STUDY & ANALYSIS OF MODERN INSTRUMENTS FOR PROCESS AUTOMATION & CONTROL- 6 months study

STUDY & ANALYSIS OF MODERN
INSTRUMENTS FOR PROCESS
AUTOMATION & CONTROL
A SIX-MONTH TRAINING COMPLETED AT IPS AUTOMATION
(CHANDIGARH)
In partial fulfillment of the requirement for the degree of
BACHELOR OF TECHNOLOGY
IN
ELECTRONICS & INSTRUMENTATION
of
Punjab Technical University(Jal.)
UNDER THE GUIDANCE OF
S. R.P.S.SAINI HARPREET SINGH
(TD. IPS) (SR. ENGINEER.IPS)
SUBMITTED BY:-
MUNISH GOYAL(315069182)
DEPARTMENT OF ELECTRONICS & INSTRUMENTATION

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GURU TEG BAHADUR KHALSA INSTITUTE OF ENGINEERING &
TECHNOLOGY
CHAPPIANWALI, MALOUT-(152107)
INDEX
Contents Page no.
Index ………………………………………………………1
Acknowledgement ………………………………….……..2
Company profile…………………………………………...3-4
Synopsis.…………………………………………………...5-7
1. Measurements……………..………………………………8
A.Pressure Measurements……………………………….9-18
a.1 Pressure Gauges & Switches………………10-13
a.2 Transducer Types……………………...…...13-14
a.3 Strain Gauges………………………………14
a.4 Capacitance Types…………………………15-16
a.5 Potentiometer………………………………17
a.6 Resonant Types…………………………….18
B. Level Measurements…………………………………19-23
b.1 Level Sensor Selection…………………….19-21
b.2 Boiling & Cryogenic Fluids………………..21-22
b.3 Sludge, Foam & Molten Metals……………22-23
C. Temperature Measurements………………………….23-25
c.1 What is temperature?……………………….24
c.2 Temp. measurement with Thermocouple.….24-25
c.3 Temp. measurement with RTD…………….25
D. Flow Measurements………………………………….26-38
d.1 Reynold numbers…………………………..27-28
d.2 Flow meter types…………………………..29
d.3 Differential pressure meters……………….29-32
d.4 Positive displacement meters……………...32-38
2. Introduction to PLC………………………………………39-93
3. Introduction to DCS……………………………………….94-116
GTBKIET:6 MONTH TRAINING 2

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ACKNOWLEDGEMENT
“A great achievement drawn with an idea grows with an effort & attains
fulfillment with our will power”. In our efforts toward the realization of our
training, we had drawn on the guidance of many people, which we are glad to
acknowledge.
I would like to express my deep sense of gratitude for all those persons who
helped me during the course of my ongoing training.
With immense gratitude, I wish to acknowledge my ineptness to my external
guide S.R.P.S.SAINI (TD. IPS AUTOMATION) who contributed with their
suggestions, counsel, guidance, encouragement & all possible help. I would also
like to thank Mr. VIJAY DUA (TD. IPS AUTOMATION), Mr. VIKAS
MARWAHA (DIR. IPS AUTOMATION), & S.HARPREET SINGH (Sr.
Engineer) .I would also like to thank MR.NITIN BANSAL (TECHNICIAN).
I am pleased to express my sincere gratitude to our internal guide for their
surmount patience & zeal in helping us at every stage, which gave us a vital
thrust.
I would like to thank all the staff members of the E&I dept. G.T.B.K.I.E.T for
the support rendered in the course of our task. A very heartful thank to our
training & placement officer for assisting us through out training period.
Last but not least I would like to thank my college faculty & all those responsible
directly & indirectly for the successful completion of my training.

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COMPANY PROFILE
INSTRUMENTATION PRODUCTS & SERVICES (IPS) AUTOMATION is
authorized distributor of ABB Instrumentation Ltd. For complete North India
including U.P & Jaipur. IPS under takes automation jobs with detail engineering
using ABB PLC’s in instrumentation areas. IPS provides the facilities to develop
a system tailored exactly to your applications.
In 1988 ABB was formed with the merger of ASEA of Switzerland & BROWN
BOVERI CORPRATION of Finland. It is one of the leading electrical
engineering companies in the world.
ABB is primarily involved in:
• Power Generation
• Power Transmission & Distribution
• Industrial & building system
• Switchgear equipments
• Process control & automation equipments
ABB is the company that utilizes technology to the maximum extent. In spite of
all this ABB has a powerful work force of 157000 engineers, placed in more than
100 countries in the world. Along with this its 120 year of service has added
another medal on chest.
This company in India has 12 manufacturing units & regional marketing offices.
ABB has employed more than 10000 people in India. Some of various products
manufactured by ABB are;
• High current rectifiers
• Static excitation system
• New generation digital devices
• relay system & panels
• Process automation & control systems
• Crane drive systems
IPS-A trusted name in control & instrumentation. Since its inception in 1992, IPS
has built up a sound reputation for being “Responsive to customer needs”. IPS
supplies primary sensors, electronic process control instruments & control panel.
It also undertakes turnkey instrumentation including system design, detailed

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engineering, procurement, erection, commissioning & maintenance. IPS also
provides micro-processor base process control & automation systems.
IPS is managed by well knit, dedicated team of young energetic members. The
members of this group are professionals with educational back-ground from
amongst the finest institutions in Engineering, Basic Sciences & Management.
• IPS offers the complete range of Process Control Instruments.
• IPS also offers Turnkey Instrumentation Projects including system
design, detailed engineering, software development, erection &
commissioning.
• IPS believes in prompt after sales services for the products
supplied through them. It has got a fully equipped service cell which
executes repair, service on products under warranty. This cell also under
takes repair & maintenance of various types of instruments. It also helps in
providing on site services & annual maintenance contract to the
customers.
Our area of interest is automation & process control products. It is concerned with
Programmable logic controllers (PLC), PID controllers, Distributed control
system (DCS), Supervisory Control and DAS (SCADA).

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SYNOPSIS
STUDY & ANALYSIS OF MODERN INSTRUMENTS
FOR PROCESS AUTOMATION & CONTROL
All of us are aware of the growth potential of the Indian economy. Our GDP growth
between 6-8% is one of the highest in the world. While we have opened the economy to
the world, the Indian industry is yet to learn how to stand in competition. Our ability to
offer world-class products & services at competitive prices is yet to be proven. With the
process of liberalization, Indian manufacturers are coming under the pressure to increase
their competitiveness in terms of quality, consistency & cost. And the only way to
achieve this is automation. But the industry needs to bring in the mindset. Manufacturers
should understand that this may not be cheap, but in the long run it surely will be cost
effective.
Automation & the Instrumentation system is going to be technological drive for energy
efficiency, effective use of industrial raw material & high tech safety.
So in order to achieve these objectives we have to use high tech devices for process
automation & control. These devices include PLC, DCS, Supervisory Control and
DAS, Control Panel, PC based control, communication between these different devices
using Profibus, Field bus, Mod bus, Inter bus etc. This is the reason why we have chosen
the above said title for 6 – month industrial Training.
The titled project has been completed at IPS in which we suited & analyzed PLC, DCS.
This report gives the reader a closer view of different modes of PLC & DCS of ABB
make their evolution, principle of operation, description of different software & hardware
devices included, their successful commissioning & operation. This report also allows the
reader to carry out a detailed analysis of these products.
PLC

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Programmable Logic Controllers were originally designed for General Motors
Corporation in 1968 to eliminate costly scrapping for assembly line relays during model
changeovers. The automotive industry fostered the development of PLC primarily
because of the massive rewiring that has to be done every time a model change occurred.
Solid-state logic is much easier to change than relay panels, and this advantage was
reflected in the cost of installation & operating the PLC instead of traditional relay
systems. Now the days PLC are no longer different from DCS. Handling analog signals
& process monitoring is also possible.
Tests like Checkup of digital & analog I/O, Power supply, Comm. Cards software,
hardware & logics is essential before sending the same for installation.
DCS
Distributed Control Systems have been evolving rapidly since mid-1980 from being
essentially panel board replacements at their inception to become comprehensive plant
information computing & control networks fully integrated into the mainstream of plant
operation. This system evolved quickly, adding video based workstation & shared
controllers capable of expressing complex unit operations oriented regulatory & sequence
control, strategies containing scores of functional element such as PID lead/lag totalizers,
dead time elements, logic circuits & general purpose calculators.
DCS are becoming distributed computing platforms with sufficient performance to
support large-scale real time process applications & scaleable to address small unit
application.
Open systems standards are enabling DCS’ s to receive information from a diverse set of
similarity compatible computing platforms, including business, laboratory information,
maintenance & other
Plant systems as well as to provide information to these systems in support of
applications.
Even with DCS systems this is still a problem to be reckoned with, because each
installation is different & requires a separate programming effort, however the
availability of standardized & tested DCS software packages for the more routine
function reduces this problem.

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SCADA
Supervisory Control & DAS (SCADA) is ABB’s Human System Interface (HSI) for
remote process control & controller applications.
SCADA portal allows faster & more natural navigation than a traditional operator
workplace. Monitoring, Controlling, Investigating exception, Studying trends are all
available with a minimum of efforts.
For today’s process control professionals, SCADA portal offers three key advantages:
1. SCADA portal is compatible with numerous communication protocols, & can
accommodate both locally & geographically distributed devices.
2. Application in SCADA portal are created using Object-Oriented Principle of
design. This enhances the quality of the application software & reduces the cost of
programming & maintaining the application.
3. SCADA portal represents a convenient points of entry to ABB’s world of
industrial IT, with scalability & upgrade capabilities as required when the control
application evolves over time.

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MEASUREMENTS
A. PRESSURE MEASUREMENT
B. LEVEL MEASUREMENT
C. TEMPERATURE MEASUREMENT
D. FLOW MEASUREMENT

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A.PRESSURE:
Pressure measurements are one of the most important measurements made in
industry especially in continuous process industries such as chemical processing and
manufacturing. The principles used in measurement of process are also applied in
the measurement of temperature, flow and liquid level.
Pressure is represented as force per unit area. As such, it has the same units as
stress and may, in general sense, be considered as a type of stress. However, the
term pressure is used for designating the force per unit area exerted by a fluid on a
containing wall. Hence, the discussion is limited to measurement of force per unit
area i.e. pressure in fluid systems.
Fluid pressure is on account of exchange of momentum between the molecules of the
fluid and a container wall. The total exchange of momentum is dependent upon the
total number of molecules striking the wall per unit time and the average velocity of
molecules. For an ideal gas we can write
Pressure, P=1/3 nm V2rms
Where n= molecular density; molecules per unit volume,
m= molecular mass; Kg
Vrms= root mean square molecular velocity; m/s
Mean free path:
The mean free path is defined as the average distance a molecule travels
between collisions.
Static and Dynamic Pressures:
When a fluid is in equilibrium, the pressure at a point is identical in all
directions and is independent of orientation. This is called static pressure.
However, when pressure gradients occur within a continuum of pressure, the
attempt to restore equilibrium results in fluid flow from regions of higher
pressure to regions of lower pressure. In this case the pressures are no longer
independent of direction and are called dynamic pressure.
Static pressure:
Static pressure may be considered as the pressure that is experienced if moving
along the stream, and the total pressure may be defined as the pressure if the

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stream is brought to rest isentrapically. The difference of the two pressures is the
pressure due to fluid motion commonly referred as the velocity pressure.
Velocity pressure = stagnation pressure- static pressure
Therefore, in order to properly interpret flow measurements, consideration
must be given how the pressure is being measured.
Absolute pressure:
It is the absolute value of force per unit area on the containing wall by a fluid.
Gauge pressure:
It represents the difference between the absolute pressure and the local
atmospheric pressure.
a.1 Pressure Gauges & Switches:
Mechanical methods of measuring pressure have been known for centuries. U-tube
manometers were among the first pressure indicators. Originally, these tubes were made
of glass, and scales were added to them as needed. But manometers are large,
cumbersome, and not well suited for integration into automatic control loops. Therefore,
manometers are usually found in the laboratory or used as local indicators. Depending on
the reference pressure used, they could indicate absolute, gauge, and differential pressure.
Differential pressure transducers often are used in flow measurement where they can
measure the pressure differential across a venturi, orifice, or other type of primary
element. The detected pressure differential is related to flowing velocity and therefore to
volumetric flow. Many features of modern pressure transmitters have come from the
differential pressure transducer. In fact, one might consider the differential pressure
transmitter the model for all pressure transducers.
"Gauge" pressure is defined relative to atmospheric conditions. In those parts of the
world that continue to use English units, gauge pressure is indicated by adding a "g" to
the units descriptor. Therefore, the pressure unit "pounds per square inch gauge" is
abbreviated psig. When using SI units, it is proper to add "gauge" to the units used, such
as "Pa gauge." When pressure is to be measured in absolute units, the reference is full
vacuum and the abbreviation for "pounds per square inch absolute" is psia.

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Often, the terms pressure gauge, sensor, transducer, and transmitter are used
interchangeably. The term pressure gauge usually refers to a self-contained indicator that
converts the detected process pressure into the mechanical motion of a pointer. A
pressure transducer might combine the sensor element of a gauge with a mechanical-to-
electrical or mechanical-to-pneumatic converter and a power supply. A pressure
transmitter is a standardized pressure measurement package consisting of three basic
components: a pressure transducer, its power supply, and a signal
conditioner/retransmitter that converts the transducer signal into a standardized output.
Pressure transmitters can send the process pressure of interest using an analog
pneumatic (3-15 psig), analog electronic (4-20 mA dc), or digital electronic signal. When
transducers are directly interfaced with digital data acquisition systems and are located at
some distance from the data acquisition hardware, high output voltage signals are
preferred. These signals must be protected against both electromagnetic and radio
frequency interference (EMI/RFI) when traveling longer distances.
Pressure transducer performance-related terms also require definition. Transducer
accuracy refers to the degree of conformity of the measured value to an accepted
standard. It is usually expressed as a percentage of either the full scale or of the actual
reading of the instrument. In case of percent-full-scale devices, error increases as the
absolute value of the measurement drops. Repeatability refers to the closeness of
agreement among a number of consecutive measurements of the same variable. Linearity
is a measure of how well the transducer output increases linearly with increasing
pressure. Hysteresis error describes the phenomenon whereby the same process pressure
results in different output signals depending upon whether the pressure is approached
from a lower or higher pressure.

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From Mechanical to Electronic:
The first pressure gauges used flexible elements as sensors. As pressure changed, the
flexible element moved, and this motion was used to rotate a pointer in front of a dial. In
these mechanical pressure sensors, a Bourdon tube, a diaphragm, or a bellows element
detected the process pressure and caused a corresponding movement.
A Bourdon tube is C-shaped and has an oval cross-section with one end of the tube
connected to the process pressure. The other end is sealed and connected to the pointer or
transmitter mechanism. To increase their sensitivity, Bourdon tube elements can be
extended into spirals or helical coils.This increases their effective angular length and
therefore increases the movement at their tip, which in turn increases the resolution of the
transducer.
Pressure Sensor Diaphragm Designs
The family of flexible pressure sensor elements also includes the bellows and the
diaphragms Diaphragms are popular because they require less space and because the
motion (or force) they produce is sufficient for operating electronic transducers. They
also are available in a wide range of materials for corrosive service applications.
After the 1920s, automatic control systems evolved, and by the 1950s pressure
transmitters and centralized control rooms were commonplace. Therefore, the free end of
a Bourdon tube (bellows or diaphragm) no longer had to be connected to a local pointer,
but served to convert a process pressure into a transmitted (electrical or pneumatic)
signal. At first, the mechanical linkage was connected to a pneumatic pressure
transmitter, which usually generated a 3-15 psig output signal for transmission over
distances of several hundred feet, or even farther with booster repeaters.
Later, as solid state electronics matured and transmission distances increased, pressure
transmitters became electronic. The early designs generated dc voltage outputs (10-50
mV; 1-5 V; 0-100 mV), but later were standardized as 4-20 mA dc current output signals.
Because of the inherent limitations of mechanical motion-balance devices, first the

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force-balance and later the solid state pressure transducer were introduced. The first
unbonded-wire strain gages were introduced in the late 1930s. In this device, the wire
filament is attached to a structure under strain, and the resistance in the strained wire is
measured. This design was inherently unstable and could not maintain calibration.
There also were problems with degradation of the bond between the wire filament and the
diaphragm, and with hysteresis caused by thermoelastic strain in the wire.The search for
improved pressure and strain sensors first resulted in the introduction of bonded thin-film
and finally diffused semiconductor strain gages. These were first developed for the
automotive industry, but shortly thereafter moved into the general field of pressure
measurement and transmission in all industrial and scientific applications.
Semiconductor pressure sensors are sensitive, inexpensive, accurate and
repeatable Many pneumatic pressure transmitters are still in operation, particularly in the
petrochemical industry. But as control systems continue to become more centralized and
computerized, these devices have been replaced by analog electronic and, more recently,
digital electronic transmitters.
Electronic Pressure Sensor Ranges
a.2 Transducer Types:
Electronic pressure sensor ranges provides an overall orientation to the scientist or
engineer who might be faced with the task of selecting a pressure detector from among
the many designs available. This table shows the ranges of pressures and vacuums that
various sensor types are capable of detecting and the types of internal references (vacuum
or atmospheric pressure) used, if any.
Because electronic pressure transducers are of greatest utility for industrial and
laboratory data acquisition and control applications, the operating principles and pros and
cons of each of these is further elaborated in this section.

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a.3 Strain Gauge:
When a strain gage, is used to measure the deflection of an elastic diaphragm or Bourdon
tube, it becomes a component in a pressure transducer. Strain gage-type pressure
transducers are widely used.
Strain-gage transducers are used for narrow-span pressure and for differential pressure
measurements. Essentially, the strain gage is used to measure the displacement of an
elastic diaphragm due to a difference in pressure across the diaphragm. These devices can
detect gauge pressure if the low pressure port is left open to the atmosphere or differential
pressure if connected to two process pressures. If the low pressure side is a sealed
vacuum reference, the transmitter will act as an absolute pressure transmitter.
Differential pressure tranducers in a variety
of ranges and outputs.
Strain gage transducers are available for pressure ranges as low as 3 inches of water to
as high as 200,000 psig (1400 MPa). Inaccuracy ranges from 0.1% of span to 0.25% of
full scale. Additional error sources can be a 0.25% of full scale drift over six months and
a 0.25% full scale temperature effect per 1000¡ F.

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a.4 Capacitance:
Capacitance pressure transducers were originally developed for use in low vacuum
research. This capacitance change results from the movement of a diaphragm element.
The diaphragm is usually metal or metal-coated quartz and is exposed to the process
pressure on one side and to the reference pressure on the other. Depending on the type of
pressure, the capacitive transducer can be either an absolute, gauge, or differential
pressure transducer.
Stainless steel is the most common diaphragm material used, but for corrosive service,
high-nickel steel alloys, such as Inconel or Hastelloy, give better performance. Tantalum
also is used for highly corrosive, high temperature applications. As a special case, silver
diaphragms can be used to measure the pressure of chlorine, fluorine, and other halogens
in their elemental state.
In a capacitance-type pressure sensor, a high-frequency, high-voltage oscillator is used to
charge the sensing electrode elements. In a two-plate capacitor sensor design, the
movement of the diaphragm between the plates is detected as an indication of the changes
in process pressure.
Capacitance-Based Pressure Cell

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The deflection of the diaphragm causes a change in capacitance that is detected by a
bridge circuit. This circuit can be operated in either a balanced or unbalanced mode. In
balanced mode, the output voltage is fed to a null detector and the capacitor arms are
varied to maintain the bridge at null. Therefore, in the balanced mode, the null setting
itself is a measure of process pressure. When operated in unbalanced mode, the process
pressure measurement is related to the ratio between the output voltage and the excitation
voltage.
Single-plate capacitor designs are also common. In this design, the plate is located on
the back side of the diaphragm and the variable capacitance is a function of deflection of
the diaphragm. Therefore, the detected capacitance is an indication of the process
pressure. The capacitance is converted into either a direct current or a voltage signal that
can be read directly by panel meters or microprocessor-based input/output boards
Capacitance pressure transducers are widespread in part because of their wide
rangeability, from high vacuums in the micron range to 10,000 psig (70 MPa).
Differential pressures as low as 0.01 inches of water can readily be measured. And,
compared with strain gage transducers, they do not drift much. Better designs are
available that are accurate to within 0.1% of reading or 0.01% of full scale. A typical
temperature effect is 0.25% of full scale per 1000¡ F.
Capacitance-type sensors are often used as secondary standards, especially in low-
differential and low-absolute pressure applications. They also are quite responsive,
because the distance the diaphragm must physically travel is only a few microns. Newer
capacitance pressure transducers are more resistant to corrosion and are less sensitive to
stray capacitance and vibration effects that used to cause "reading jitters" in older
designs.

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a.5 Potentiometer:
The potentiometric pressure sensor provides a simple method for obtaining an electronic
output from a mechanical pressure gauge. The device consists of a precision
potentiometer, whose wiper arm is mechanically linked to a Bourdon or bellows element.
The movement of the wiper arm across the potentiometer converts the mechanically
detected sensor deflection into a resistance measurement, using a Wheatstone bridge
circuit.
The mechanical nature of the linkages connecting the wiper arm to the Bourdon tube,
bellows, or diaphragm element introduces unavoidable errors into this type of
measurement. Temperature effects cause additional errors because of the differences in
thermal expansion coefficients of the metallic components of the system. Errors also will
develop due to mechanical wear of the components and of the contacts.
Potentiometric transducers can be made extremely small and installed in very tight
quarters, such as inside the housing of a 4.5-in. dial pressure gauge. They also provide a
strong output that can be read without additional amplification. This permits them to be
used in low power applications. They are also inexpensive. Potentiometric transducers
can detect pressures between 5 and 10,000 psig (35 KPa to 70 MPa). Their accuracy is
between 0.5% and 1% of full scale, not including drift and the effects of temperature.

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a.6 Resonant Wire:
The resonant-wire pressure transducer was introduced in the late 1970s. A wire is gripped
by a static member at one end, and by the sensing diaphragm at the other. An oscillator
circuit causes the wire to oscillate at its resonant frequency. A change in process pressure
changes the wire tension, which in turn changes the resonant frequency of the wire. A
digital counter circuit detects the shift. Because this change in frequency can be detected
quite precisely, this type of transducer can be used for low differential pressure
applications as well as to detect absolute and gauge pressures.
The most significant advantage of the resonant wire pressure transducer is that it
generates an inherently digital signal, and therefore can be sent directly to a stable crystal
clock in a microprocessor. Limitations include sensitivity to temperature variation, a
nonlinear output signal, and some sensitivity to shock and vibration. These limitations
typically are minimized by using a microprocessor to compensate for nonlinearities as
well as ambient and process temperature variations.
Resonant wire transducers can detect absolute pressures from 10 mm Hg, differential
pressures up to 750 in. water, and gauge pressures up to 6,000 psig (42 MPa). Typical
accuracy is 0.1% of calibrated span, with six-month drift of 0.1% and a temperature
effect of 0.2% per 1000¡ F.
B. A Level Measurement Orientation:

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On the 28th of March, 1979, thousands of people fled from Three Mile Island (near
Harrisburg, PA) when the cooling system of a nuclear reactor failed. This dangerous
situation.
developed because the level controls turned off the coolant flow to the reactor when
they detected the presence of cooling water near the top of the tank. Unfortunately,
the water reached the top of the reactor vessel not because there was too much
water in the tank, but because there was so little that it boiled and swelled to the
top. From this example, we can see that level measurement is more complex than
simply the determination of the presence or absence of a fluid at a particular
elevation.
b.1 Level Sensor Selection:
When determining what type of level sensor should be used for a given application,
there are a series of questions that must be answered:
Can the level sensor be inserted into the tank or should it be completely external?
Should the sensor detect the level continuously or will a point sensor be adequate?
Can the sensor come in contact with the process fluid or must it be located in the
vapor space?
Is direct measurement of the level needed or is indirect detection of hydrostatic head
(which responds to changes in both level and density) acceptable?
Is tank depressurization or process shut-down acceptable when sensor removal or
maintenance is required?
By evaluating the above choices, one will substantially shorten the list of sensors to
consider. The selection is further narrowed by considering only those designs that
can be provided in the required materials of construction and can function at the
required accuracy, operating temperature, etc. (Table 4). When the level to be
measured is a solid, slurry, foam, or the interface between two liquid layers, it is
advisable to consult not only Table 4, but other recommendations, such as Table 5.
If it is found that a number of level detector designs can satisfy the requirements of
the application, one should also consider the traditions or preferences of the
particular plant or the particular process industry, because of user familiarity and the
availability of spare parts. For example, the oil industry generally prefers
displacement-type level sensors, while the chemical industry favors differential
pressure (d/p) cells. (The petroleum industry will use d/p cells when the span
exceeds 60-80 in.)

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If the tank is agitated, there is often no space in which to insert probe-type sensors.
Plus, because the liquid surface is not flat, sonic, ultrasonic, or radar devices typically
cannot be used, either. Even with displacer or d/p sensors, agitation can cause the
level signal to cycle. These pulses can be filtered out by first determining the
maximum rate at which the level can change (due to filling or discharging) and
disregarding any change that occurs faster than that.
The relationship between level and tank volume is a function of the cross-sectional
shape of the tank. With vertical tanks, this relationship is linear, while with horizontal
or spherical vessels, it is a non-linear relationship.
If the level in a tank is to be inferred using hydrostatic pressure measurement, it is
necessary to use multi-transmitter systems when it is desirable to:
Detect the true level, while either the process temperature or density varies;
Measure both level and density; and
Measure the volume and the mass (weight) in the tank.
By measuring one temperature and three pressures, the system shown in Figure is
capable of simultaneously measuring volume (level), mass (weight), and density, all
with an accuracy of 0.3% of full span.

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b.2 Boiling & Cryogenic Fluids:
When a d/p cell is used to measure the level in a steam drum, a reverse-acting
transmitter is usually installed . An uninsulated condensing chamber is used to
connect the high pressure (HP) side of the d/p cell to the vapor space on the top of
the drum. The steam condenses in this chamber and fills the wet leg with ambient
temperature water, while the low pressure (LP) side of the d/p cell detects the
hydrostatic head of the boiling water inside the drum. The output of the d/p cell
reflects the amount of water in the drum. Output rises as the mass of water in the
drum drops (because the steaming rate and the associated swelling increase). It is
for this reason that a reverse acting d/p cell is recommended for this application.
When the process fluid is liquid nitrogen (or some other cryogenic material), the tank
is usually surrounded by a thermally insulated and evacuated cold box. Here, the low
pressure (LP) side of a direct acting d/p cell is connected to the vapor space above
the cryogenic liquid. As the liquid nitrogen approaches the HP side of the d/p cell
(which isat ambient temperature outside the cold box), its temperature rises. When
the temperature reaches the boiling point of nitrogen, it will boil and,

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from that point on, the connecting line will be filled with nitrogen vapor. This can
cause noise in the level measurement. To protect against this, the liquid filled portion
of the connecting line should be sloped back towards the tank. The cross-section of
the line should be large (about 1 inch in diameter) to minimize the turbulence caused
by the simultaneous boiling and re-condensing occurring at the liquid-vapor
interface.
b.3 Sludge, Foam, & Molten Metals:
Many process fluids are aggressive or difficult to handle and it's best to
avoid physical contact with them. This can be accomplished by placing the level
sensor outside the tank (weighing, radiation) or locating the sensor in the vapor
space (ultrasonic, radar, microwave) above the process fluid. When these options are
not available or acceptable, one must aim to minimize maintenance and physical
contact with the process fluid.
When the process fluid is a sludge, slurry, or a highly viscous polymer, and the goal
is to detect the level at one point, the design shown in Figure is commonly
considered. The ultrasonic or optical signal source and receiver typically are
separated by more than six inches so that the process fluid drains freely from the
intervening space. After a high-level episode, an automatic washing spray is
activated.
When the sludge or slurry level is detected continuously, one of the goals is to
eliminate dead-ended cavities where the sludge might settle. In addition, all surfaces
which are exposed to the process fluid should be covered with Teflon®. such an
installation, employing Teflon®-coated extended diaphragms to minimize material
buildup.
In strippers, where the goal is to drive off the solvent in the shortest period of time,
one aims to keep the foam level below a maximum. In other processes, it is
desirable to separately control both the liquid level beneath the foam and the
thickness of the foam. In the paper industry, beta radiation detectors are used for
such applications (Kraft processing), while other industries detect the degree of
foaming indirectly (by measuring related variables, such as heat input or vapor flow),
or they use capacitance, conductivity, tuning fork, optical, or thermal switches, all
provided with automatic washers.

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Measuring the level of molten glass or metals is another special application. The
most expensive (but also most accurate) technique available is proximity
capacitance-based level measurement, which can provide a resolution of 0.1 mm
over a range of 6 in. Laser-based systems can provide even better resolution from
distances up to 2 ft. If such high resolution is not required and cost is a concern, one
can make a float out of refractory material and attach a linear variable differential
transformer (LVDT), or make a bubbler tube out of refractory material and bubble
argon or nitrogen through it.
C. TEMPERATURE:
Temperature measurement are amongst the most common and the most important
measurements made in controlling industrial processes. The precise control of temperature
is key factor in process industry especially those which involve chemical operations.
Consequently, it is most important to make a comprehensive survey of methods of
measurement of temperature and their advantages and disadvantages. It is equally
important to have information about the operating limitations in terms of time of response,
temperature range, distance of operation and compatability with other control elements.
This will permit one to select the best method of measurement for a particular application.
The measurement of temperature is done in many diverse fields like measuring temperature
of a household oven, of a distant planet, of a red hot blume of iron being rolled, of parts of
human body, of windings of electricals machines, of bearings of steam turbines etc.
Temperature is not measured directly like displacement, pressure or flow are but is
measured through indirect means. Change of temperature of a substance causes a
variety of effects. These effects may be physical, chemical, electrical or optical and
they may be used for the measurement of temperature through use of proper
temperature sensing devices. They change with temperature and these changes can
be used to measure temperature. Calibration may be achieved through comparison
with established standards.
CLASSIFICATION OF TEMPERATURE MEASUREMENT DEVICES
There are many basis for classification of temp. measuring instruments. These
devices can be classified on the basis of:
1. Nature of change produced in the temp sensing element or the phenomenon
used
for production of a change due to temperature.
a. Those which are primarily electrical or electronic in nature and
b. Those which do not employ electrical and electronic methods for
their working.
1. Electrical and non-electrical operatinf principles.
2. Temperature range of the instrument

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Temperature Measurement Basics:
c.1 What is Temperature?
Qualitatively, the temperature of an object determines the sensation of warmth or coldness
felt by touching it. More specifically, temperature is a measure of the average kinetic
energy of the particles in a sample of matter, expressed in units of degrees on a standard
scale.
There are numerous technologies and sensors for measuring temperature, however, two of
the most common types of sensors are thermocouples and RTDs. See how to measure
temperature with a thermocouple and an RTD below.
c.2 Temperature Measurement With A Thermocouple
You cannot simply connect the thermocouple to a voltmeter or other measurement system
to measure a thermocouple Seebeck voltage. This is because connecting the thermocouple
wires to the measurement system creates additional thermoelectric circuits.
Consider the circuit illustrated in Figure 1. A J-type thermocouple is in a candle flame that
has a temperature you want to measure. The two thermocouple wires are connected to the
copper leads of a DAQ board. Notice that the circuit contains three dissimilar metal
junctions -- J1, J2, and J3. J1, the thermocouple junction, generates a Seebeck voltage
proportional to the temperature of the candle flame. J2 and J3 each have their own Seebeck
coefficient and generate their own thermoelectric voltage proportional to the temperature at
the DAQ terminals. To determine the voltage contribution from J1, you need to know the
temperatures of junctions J2 and J3 as well as the voltage-to-temperature relationships for
these junctions. You can then subtract the contributions of the parasitic junctions at J2 and
J3 from the measured voltage at junction J1.
Thermocouples require some form of temperature reference to compensate for these
unwanted parasitic "cold" junctions. The most common method of cold junction
compensation is to measure the temperature at the reference junction with a direct-reading
temperature sensor and subtract the parasitic junction voltage contributions. This process is
called cold-junction compensation. You can simplify computing cold-junction

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compensation by taking advantage of some thermocouple characteristics.
c.3 Temperature Measurement With a RTD or Thermistor
Because RTDs and thermistors are resistive devices, you must supply them with an
excitation current and then read the voltage across their terminals. If extra heat cannot be
dissipated, I2R heating caused by the excitation current can raise the temperature of the
sensing element above that of the ambient temperature. Self-heating will actually change
the resistance of the RTD or thermistor, causing error in the measurement. The effects of
self-heating can be minimized by supplying lower excitation current.
RTD and thermistor output signals are typically in the millivolt range, making them
susceptible to noise. Low-pass filters are commonly available in RTD and thermistor data
acquisition systems, and they can effectively eliminate high-frequency noise in RTD and
thermistor measurements. For instance, low-pass filters are useful for removing the 60 Hz
power line noise that is prevalent in most laboratory and plant settings.
You can also significantly improve the noise performance of your system by amplifying
the low-level RTD and thermistor voltages near the signal source. Because RTD and
thermistor output voltage levels are very low, you should choose a gain that optimizes the
input limits of the analog-to-digital converter (ADC).
The easiest way to connect an RTD or thermistor to a measurement device is with a 2-wire
connection.
With this method, the two wires that provide the RTD or thermistor with its excitation
current are also used to measure the voltage across the sensor. Because of the low nominal
resistance of RTDs, measurement accuracy can be drastically affected by lead wire
resistance. For example, lead wires with a resistance of 1? Connected to a 100? Platinum
RTD cause a 1 percent measurement error.
D. Flow Reference Section:
An overview of types and capabilities, plus guidelines on selection, installation, and
maintenance

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INTRODUCTION
Measuring the flow of liquids is a critical need in many industrial plants. In some
operations, the ability to conduct accurate flow measurements is so important that it can
make the difference between making a profit or taking a loss. In other cases, inaccurate
flow measurements or failure to take measurements can cause serious (or even disastrous)
results.
With most liquid flow measurement instruments, the flow rate is determined inferentially
by measuring the liquid's velocity or the change in kinetic energy. Velocity depends on
the pressure differential that is forcing the liquid through a pipe or conduit. Because the
pipe's cross-sectional area is known and remains constant, the average velocity is an
indication of the flow rate. The basic relationship for determining the liquid's flow rate in
such cases is:
Q = V x A
Where
Q = liquid flow through the pipe
V = average velocity of the flow
A = cross-sectional area of the pipe
Other factors that affect liquid flow rate include the liquid's viscosity and density, and the
friction of the liquid in contact with the pipe.
Direct measurements of liquid flows can be made with positive-displacement flowmeters.
These units divide the liquid into specific increments and move it on. The total flow is an
accumulation of the measured increments, which can be counted by mechanical or
electronic techniques.
d.1 Reynolds Numbers
The performance of flow meters is also influenced by a dimensionless unit called the
Reynolds Number. It is defined as the ratio of the liquid's inertial forces to its drag forces.

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Laminar and turbulent flow are two types normally encountered in liquid flow
Measurement operations. Most applications involve turbulent flow, with R values
above 3000. Viscous liquids usually exhibit laminar flow, with R values below 2000.
The transition zone between the two levels may be either laminar or turbulent.
The equation is:
R = 3160 x Q x Gt
D x µ
Where:
R = Reynolds number
Q = liquid's flow rate, gpm
Gt = liquid's specific gravity
D = inside pipe diameter, in.
µ = Liquid’s viscosity, cp

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The flow rate and the specific gravity are inertia
forces, and the pipe diameter and viscosity are drag
forces. The pipe diameter and the specific gravity
remain constant for most liquid applications. At
very low velocities or high viscosities, R is low, and
the liquid flows in smooth layers with the highest
velocity at the center of the pipe and low velocities
at the pipe wall where the viscous forces restrain it.
This type of flow is called laminar flow. R values
are below approximately 2000. A characteristic of
laminar flow is the parabolic shape of its velocity
profile.
However, most applications involve turbulent flow,
with R values above 3000. Turbulent flow occurs at
high velocities or low viscosities. The flow breaks
up into turbulent eddies that flow through the pipe
with the same average velocity. Fluid velocity is
less significant, and the velocity profile is much
more uniform in shape. A transition zone exists
between turbulent and laminar flows. Depending on
the piping configuration and other installation
conditions, the flow may be either turbulent or
laminar in this zone.

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d.2 FLOWMETER TYPES:
Numerous types of flow meters are available for closed-piping systems. In general, the
equipment can be classified as differential pressure, positive displacement, velocity, and
mass meters. Differential pressure devices (also known as head meters) include orifices,
venturi tubes, flow tubes, flow nozzles, pitot tubes, elbow-tap meters, target meters, and
variable-area meters.
Positive displacement meters include piston, oval-gear, nutating-disk, and rotary-vane
types. Velocity meters consist of turbine, vortex shedding, electromagnetic, and sonic
designs. Mass meters include Coriolis and thermal types. The measurement of liquid
flows in open channels generally involves weirs and flumes.
Space limitations prevent a detailed discussion of all the liquid flowmeters available
today. However, summary characteristics of common devices
d.3 Differential Pressure Meters:
The use of differential pressure as an inferred measurement of a liquid's rate of flow is
well known. Differential pressure flowmeters are, by far, the most common units in use
today. Estimates are that over 50 percent of all liquid flow measurement applications use
this type of unit.
The basic operating principle of differential pressure flowmeters is based on the premise
that the pressure drop across the meter is proportional to the square of the flow rate. The
flow rate is obtained by measuring the pressure differential and extracting the square root.
Differential pressure flowmeters, like most flowmeters, have a primary and secondary
element. The primary element causes a change in kinetic energy, which creates the
differential pressure in the pipe. The unit must be properly matched to the pipe size, flow
conditions, and the liquid's properties. And, the measurement accuracy of the element
must be good over a reasonable range. The secondary element measures the differential
pressure and provides the signal or read-out that is converted to the actual flow value.
Orifices are the most popular liquid flowmeters in use today. An orifice is simply a flat
piece of metal with a specific-sized hole bored in it. Most orifices are of the concentric
type, but eccentric, conical (quadrant), and segmental designs are also available.
In practice, the orifice plate is installed in the pipe between two flanges. Acting as the
primary device, the orifice constricts the flow of liquid to produce a differential pressure
across the plate. Pressure taps on either side of the plate are used to detect the difference.
Major advantages of orifices are that they have no moving parts and their cost does not
increase significantly with pipe size.

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Conical and quadrant orifices are relatively new. The units were developed primarily to
measure liquids with low Reynolds numbers. Essentially constant flow coefficients can
be maintained at R-values below 5000. Conical orifice plates have an upstream bevel, the
depth and angle of which must be calculated and machined for each application.
The segmental wedge is a variation of the segmental orifice. It is a restriction orifice
primarily designed to measure the flow of liquids containing solids. The unit has the
ability to measure flows at low Reynolds numbers and still maintain the desired square-
root relationship. Its design is simple, and there is only one critical dimension the wedge
gap. Pressure drop through the unit is only about half that of conventional orifices.
I
Integral wedge assemblies combine the wedge element and pressure taps into a one-piece
pipe coupling bolted to a conventional pressure transmitter. No special piping or fittings
are needed to install the device in a pipeline.
Metering accuracy of all orifice flowmeters depends on the installation conditions, the
orifice area ratio, and the physical properties of the liquid being measured.

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Venturi tubes have the advantage of being able to handle large flow volumes at low-
pressure drops. A venturi tube is essentially a section of pipe with a tapered entrance and
a straight throat. As liquid passes through the throat, its velocity increases, causing a
pressure differential between the inlet and outlet regions.
The flowmeters have no moving parts. They can be installed in large diameter pipes
using flanged, welded or threaded-end fittings. Four or more pressure taps are usually
installed with the unit to average the measured pressure. Venturi tubes can be used with
most liquids, including those having a high solids content.
Flow tubes are somewhat similar to venturi tubes except that they do not have the
entrance cone. They have a tapered throat, but the exit is elongated and smooth. The
distance between the front face and the tip is approximately one-half the pipe diameter.
Pressure taps are located about one-half pipe diameter downstream and one pipe diameter
upstream.
Flow Nozzles, at high velocities, can handle approximately 60 percent greater liquid flow
than orifice plates having the same pressure drop. Liquids with suspended solids can also
be metered. However, use of the units is not recommended for highly viscous liquids or
those containing large amounts of sticky solids.
Pitot tubes sense two pressures simultaneously, impact and static. The impact unit
consists of a tube with one end bent at right angles toward the flow direction. The static
tube's end is closed, but a small slot is located in the side of the unit. The tubes can be
mounted separately in a pipe or combined in a single casing.
Pitot tubes are generally installed by welding a coupling on a pipe and inserting the probe
through the coupling. Use of most pitot tubes is limited to single point measurements.
The units are susceptible to plugging by foreign material in the liquid. Advantages of
pitot tubes are low cost, absence of moving parts, easy installation, and minimum
pressure drop.
Elbow meters operate on the principle that when liquid travels in a circular path,
centrifugal force is exerted along the outer edges. Thus, when liquid flows through a pipe
elbow, the force on the elbow's interior surface is proportional to the density of the liquid
times the square of its velocity. In addition, the force is inversely proportional to the
elbow's radius.
Any 90 deg. pipe elbow can serve as a liquid flowmeter. All that is required is the
placement of two small holes in the elbow's midpoint (45 deg. point) for piezometer taps.
Pressure-sensing lines can be attached to the taps by using any convenient method.
Target meters sense and measure forces caused by liquid impacting on a target or drag-
disk suspended in the liquid stream. A direct indication of the liquid flow rate is achieved
by measuring the force exerted on the target. In its simplest form, the meter consists only

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of a hinged, swinging plate that moves outward, along with the liquid stream. In such
cases, the device serves as a flow indicator.
A more sophisticated version uses a precision, low-level force transducer-sensing
element. The force of the target caused by the liquid flow is sensed by a strain gage. The
output signal from the gage is indicative of the flow rate. Target meters are useful for
measuring flows of dirty or corrosive liquids.
Variable-area meters, often called rotameters, consist essentially of a tapered tube and a
float. Although classified as differential pressure units, they are, in reality, constant
differential pressure devices. Flanged-end fittings provide an easy means for installing
them in pipes. When there is no liquid flow, the float rests freely at the bottom of the
tube. As liquid enters the bottom of the tube, the float begins to rise. The position of the
float varies directly with the flow rate. Its exact position is at the point where the
differential pressure between the upper and lower surfaces balance the weight of the float.
Because the flow rate can be read directly on a scale mounted next to the tube, no
secondary flow-reading devices are necessary. However, if desired, automatic sensing
devices can be used to sense the float's level and transmit a flow signal. Rotameter tubes
are manufactured from glass, metal, or plastic. Tube diameters vary from 1/4 to greater
than 6 in.
d.4 Positive-Displacement Meters:
Operation of these units consists of separating liquids into accurately measured
increments and moving them on. Each segment is counted by a connecting register.
Because every increment represents a discrete volume, positive-displacement units are
popular for automatic batching and accounting applications. Positive-displacement
meters are good candidates for measuring the flows of viscous liquids or for use where a
simple mechanical meter system is needed.

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Reciprocating piston meters are of the single and multiple-piston types. The specific
choice depends on the range of flow rates required in the particular application. Piston
meters can be used to handle a wide variety of liquids. A magnetically driven, oscillating
piston meter is shown in Fig. Liquid never comes in contact with gears or other parts that
might clog or corrode.
Oval-gear meters have two rotating, oval-shaped gears with synchronized, close fitting
teeth. A fixed quantity of liquid passes through the meter for each revolution. Shaft
rotation can be monitored to obtain specific flow rates.
Nutating-disk meters have a moveable disk mounted on a concentric sphere located in a
spherical side-walled chamber. The pressure of the liquid passing through the measuring
chamber causes the disk to rock in a circulating path without rotating about its own axis.
It is the only moving part in the measuring chamber.
A pin extending perpendicularly from the disk is connected to a mechanical counter that
monitors the disk's rocking motions. Each cycle is proportional to a specific quantity of
flow. As is true with all positive-displacement meters, viscosity variations below a given
threshold will affect measuring accuracies. Many sizes and capacities are available. The
units can be made from a wide selection of construction materials.
Rotary-vane meters are available in several designs, but they all operate on the same
principle. The basic unit consists of an equally divided, rotating impeller (containing two
or more compartments) mounted inside the meter's housing. The impeller is in continuous
contact with the casing. A fixed volume of liquid is swept to the meter's outlet from each
compartment as the impeller rotates. The revolutions of the impeller are counted and
registered in volumetric units.
Helix flowmeters consist of two radically pitched helical rotors geared together, with a
small clearance between the rotors and the casing. The two rotors displace liquid axially
from one end of the chamber to the other.
Velocity Meters
These instruments operate linearly with respect to the volume flow rate. Because there is
no square-root relationship (as with differential pressure devices), their range ability is
greater. Velocity meters have minimum sensitivity to viscosity changes when used at
Reynolds numbers above 10,000. Most velocity-type meter housings are equipped with
flanges or fittings to permit them to be connected directly into pipelines.

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Turbine meters have found widespread use for accurate liquid measurement
applications. The unit consists of a multiple-bladed rotor mounted with a pipe,
perpendicular to the liquid flow. The rotor spins as the liquid passes through the blades.
The rotational speed is a direct function of flow rate and can be sensed by magnetic pick-
up, photoelectric cell, or gears. Electrical pulses can be counted and totalized.
The number of electrical pulses counted for a given period of time is directly proportional
to flow volume. A tachometer can be added to measure the turbine's rotational speed and
to determine the liquid flow rate. Turbine meters, when properly specified and installed,
have good accuracy, particularly with low-viscosity liquids.
A major concern with turbine meters is bearing wear. A "bearingless" design has been
developed to avoid this problem. Liquid entering the meter travels through the spiraling
vanes of a stator that imparts rotation to the liquid stream. The stream acts on a sphere,
causing it to orbit in the space between the first stator and a similarly spiraled
secondstator. The orbiting movement of the sphere is detected electronically. The
frequency of the resulting pulse output is proportional to flow rate.
Vortex meters make use of a natural phenomenon that occurs when a liquid flows
around a bluff object. Eddies or vortices are shed alternately downstream of the object.
The frequency of the vortex shedding is directly proportional to the velocity of the liquid
flowing through the meter.
The three major components of the flowmeter are a bluff body strut-mounted across the
flowmeter bore, a sensor to detect the presence of the vortex and to generate an electrical
impulse, and a signal amplification and conditioning transmitter whose output is
proportional to the flow rate. The meter is equally suitable for flow rate or flow
totalization measurements. Use for slurries or high viscosity liquids is not recommended.

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Electromagnetic meters can handle most liquids and slurries, providing that the material
being metered is electrically conductive. Major components are the flow tube (primary
element). The flow tube mounts directly in the pipe. Pressure drop across the meter is the
same as it is through an equivalent length of pipe because there are no moving parts or
obstructions to the flow. The voltmeter can be attached directly to the flow tube or can be
mounted remotely and connected to it by a shielded cable.
Electromagnetic flowmeters operate on Faraday's law of electromagnetic induction that
states that a voltage will be induced when a conductor moves through a magnetic field.
The liquid serves as the conductor; the magnetic field is created by energized coils
outside the flow tube. The amount of voltage produced is directly proportional to the flow
rate. Two electrodes mounted in the pipe wall detect the voltage, which is measured by
the secondary element.
Electromagnetic flowmeters have major advantages: They can measure difficult and
corrosive liquids and slurries; and they can measure forward as well as reverse flow with
equal accuracy. Disadvantages of earlier designs were high power consumption, and the
need to obtain a full pipe and no flow to initially set the meter to zero. Recent
improvements have eliminated these problems. Pulse-type excitation techniques have
reduced power consumption, because excitation occurs only half the time in the unit.
Zero settings are no longer required.
Ultrasonic flowmeters can be divided into Doppler meters and time-of-travel (or transit)
meters. Doppler meters measure the frequency shifts caused by liquid flow. Two
transducers are mounted in a case attached to one side of the pipe. A signal of known
frequency is sent into the liquid to be measured. Solids, bubbles, or any discontinuity in
the liquid, cause the pulse to be reflected to the receiver element. Because the liquid
causing the reflection is moving, the frequency of the returned pulse is shifted. The
frequency shift is proportional to the liquid's velocity.
A portable Doppler meter capable of being operated on AC power or from a rechargeable
power pack has recently been developed. The sensing heads are simply clamped to the
outside of the pipe, and the instrument is ready to be used. Total weight, including the
case, is 22 lb. A set of 4 to 20 millampere output terminals permits the unit to be
connected to a strip chart recorder or other remote device.
Time-of-travel meters have transducers mounted on each side of the pipe. The
configuration is such that the sound waves traveling between the devices are at a 45 deg.
angle to the direction of liquid flow. The speed of the signal traveling between the
transducers increases or decreases with the direction of transmission and the velocity of
the liquid being measured. A time-differential relationship proportional to the flow can be
obtained by transmitting the signal alternately in both directions. A limitation of time-of-
travel meters is that the liquids being measured must be relatively free of entrained gas or
solids to minimize signal scattering and absorption.

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Mass Flowmeters The continuing need for more accurate flow measurements in mass-
related processes (chemical reactions, heat transfer, etc.) has resulted in the development
of mass flowmeters. Various designs are available, but the one most commonly used for
liquid flow applications is the Coriolis meter. Its operation is based on the natural
phenomenon called the Coriolis force, hence the name.
Coriolis meters are true mass meters that measure the mass rate of flow directly as
opposed to volumetric flow. Because mass does not change, the meter is linear without
having to be adjusted for variations in liquid properties. It also eliminates the need to
compensate for changing temperature and pressure conditions. The meter is especially
useful for measuring liquids whose viscosity varies with velocity at given temperatures
and pressures.

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Coriolis meters are also available in various designs. A popular unit consists of a U-
shaped flow tube enclosed in a sensor housing connected to an electronics unit. The
sensing unit can be installed directly into any process. The electronics unit can be located
up to 500 feet from the sensor.
Inside the sensor housing, the U-shaped flow tube is vibrated at its natural frequency by a
magnetic device located at the bend of the tube. The vibration is similar to that of a
tuning fork, covering less than 0.1 in. and completing a full cycle about 80 times/sec. As
the liquid flows through the tube, it is forced to take on the vertical movement of the
tube, Fig. When the tube is moving upward during half of its cycle, the liquid flowing
into the meter resists being forced up by pushing down on the tube.
Having been forced upward, the liquid flowing out of the meter resists having its vertical
motion decreased by pushing up on the tube. This action causes the tube to twist. When
the tube is moving downward during the second half of its vibration cycle, it twists in the
opposite direction.
Having been forced upward, the liquid flowing out of the meter resists having its vertical
motion decreased by pushing up on the tube. This action causes the tube to twist. When
the tube is moving downward during the second half of its vibration cycle, it twists in the
opposite direction. The amount of twist is directly proportional to the mass flow rate of
the liquid flowing through the tube. Magnetic sensors located on each side of the flow
tube measure the tube velocities, which change as the tube twists. The sensors feed this
information to the electronics unit, where it is processed and converted to a voltage
proportional to mass flow rate. The meter has a wide range of applications from
adhesives and coatings to liquid nitrogen.

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Thermal-type mass flowmeters have traditionally been used for gas measurements, but
designs for liquid flow measurements are available. These mass meters also operate
independent of density, pressure, and viscosity. Thermal meters use a heated sensing
element isolated from the fluid flow path. The flow stream conducts heat from the
sensing element. The conducted heat is directly proportional to the mass flow rate. The
sensor never comes into direct contact with the liquid. The electronics package includes
the flow analyzer, temperature compensator, and a signal conditioner that provides a
linear output directly proportional to mass flow.
PROGRAMMING THE KLOCKNER MOELLER EASY
MINI - PLC

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This is a front view of the
Moeller Klockner EASY
programmable controller.
There are 4 pushbuttons, DEL,
ALT, ESC and OK, which are
used to program and operate
the unit.
The large round cursor disk is
used to move around menus or
circuit diagrams and is
operated by pressing near the
top, bottom right or left edge.
The OK button is used to select
menu functions highlighted by
the cursor.
`

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Table of Contents:-
Programming Screens
• Status Screen
• Main Menu
• Program Menu
• Circuit Diagram
Basic Programming Steps
• Entering your program
• Setting Parameters
Available Functions
• Variables Negation
• Output Relays
• Output Relay Contacts
• Marker relays
• Counter Relays
• Timers
• Clock Controllers
• Analog Comparators
• P-Buttons
• "If" Jumps
• Text Display
System Settings
• System Screen
• Password Protection
• Menu Language
• Debounce
• Activating P-Buttons
• Startup Mode
• Retention
Memory Modules
• Archive or Copy a Program
Expansion Units
• Join 2 units for increased capacity
Physical Wiring

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• Connecting Inputs, Outputs and Power Supply
Specifications
• Ratings & Technical Information

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The Programming Screens
Figure 1
Status Screen: this shows the condition of the inputs (I) and the
outputs (Q). In this case, inputs 3 & 5 are activated and output
relay 2 is closed.
"RUN" indicates the unit is currently running the program.
On models that have the clock, the "WE" on the right indicates
"Wednesday" and below that is the time of day in 24 hour
format.
Press the OK button, for the Main Menu.
Figure 2
Main Menu: You may move up and down using the cursor
arrows on the large disk, your present selection is blinking.
Selecting "PROGRAM" takes you to the program menu.
"RUN" is the start button to begin processing, and means the
unit is currently in stop mode. If you see a "STOP" button, the
unit is in run mode, and pressing it will stop processing.
"PARAMETER" is used to set-up various counters, timers, etc.
On models with the clock, you will also have the "SET CLOCK"
option.
Use the OK button to make your selection.
Figure 3
Program Menu: To begin programming or to view the circuit
diagram, select PROGRAM and press the OK button.
Or, to delete your existing program, select "DELETE PROG"
and press the OK button.

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Figure 4
Circuit Diagram: This screen begins as a blank, and you type in
your desired program. This simple program has only one
function: If input 1 (I1) is activated then output relay 1 (Q1) is
activated.
After you have entered your program, simply hit the ESC button
until the Main Menu appears, then select RUN and hit OK.
Figure 5
Circuit Diagram: Power the unit up, then press the OK button 3
times and you will arrive at the blank screen where you will
enter your program.
We will now write a simple program, which will activate output
Q1 when input I1 OR I2 are activated, and will activate output
Q2 when both inputs I1 AND I2 are activated.
Figure 6
Begin with the blank screen and your blinking cursor is in the
upper left corner. Note that the screen is 4 columns wide, which
allows for 3 contacts plus one coil on the right.
Press OK, and I1 will appear, indicating Input 1.
Now use the cursor arrow to move all the way to the right and
press OK again and the symbol {Q1 will appear, indicating
Output 1.
Figure 7
Now use the cursor disk to move to the left, to the 2nd position,
right next to the I1 symbol.
Press the ALT button and the line drawing tool appears. Use the
cursor again to move the line drawing tool to the right, twice.
Now press the ALT button again, to turn the line drawing tool
off.
The input I1 and the output relay Q1 are now "wired" together.

315069182/E&I/03L
Figure 8
Now use the cursor to move to the 2nd row, all the way to the
left. Here, press the OK button, and I1 appears.
But we wanted I2 here, so use the cursor to move one character
to the right, to the "1". Here use the up cursor to change the "1"
to a "2" and you will have "I2". Press OK to select it.
You are now at the 2nd column so press ALT for the line
drawing tool, and "wire" input 2 as shown, and then press ALT
again to turn the line tool off.
Figure 9
Now move down to the 3rd line, and press OK twice to enter I1.
Note you may use the same input symbol repeatedly.
In the next column you press OK and I1 appears, pressing OK
again moves you to the "1" of the "I1" and uses the UP cursor to
change it to "I2" and press OK to select it. Notice the "wires"
appear automatically.
Move to the far right column and press OK and {Q1 appears,
which you will change to {Q2.
Figure 10
Fill in any missing "wires" and you're done!
Press ESC a few times to reach the Main Menu, and select RUN
and press OK and your program is running.
Programming Parameters: Here is a program using a timer.
Timers need parameters set for on-delay or off-delay, time, etc.
Enter the symbols shown at left. When you put in the TT1 timer
coil, a {Q1 will appear, use the UP cursor to change it to TT1.

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Figure 11
When you enter the T1 contact, an I1 will appear, again use the
UP cursor to change it to T1, and when you press OK to select it,
the parameter display will appear.
Note, timers are set-up at the contact, not at the coil.
Figure 12
Parameter Display: Shown here is a typical parameter display.
In the case of a timer, the top left symbol indicates type (on-
delay, off-delay, etc), in this case the X means "on-delay".
Below that the "S" indicates "seconds". The number at the top
(01.14) is the actual time that has elapsed and the number below
it (07.00) is the preset time.
You can move around the parameter display using only the right
and left cursor. Use the up and down cursors to change
individual values. More specific information appears in the next
section below.
Figure 13
Illegal: If you have more than 4 symbols to place on one line,
you could do it the way shown, but THIS WON'T WORK!
"Power" flows only to the right. Instead, use 3 symbols and a
"marker relay" coil, then place a contact from the marker relay at
the beginning of the next line, then continue on.
See the section on "marker relays" for the correct method.
Figure 14
Negation: Relay circuits often require "closed contacts" and
this is done with negation. Simply move to any contact on
your diagram and press OK to select it. Then press ALT, and
a small line will appear above the symbol. This is now a
"normally closed" contact. This works for any type of contact,
timers, counters, clocks, etc.
In the picture here the output relay Q1 will be energized
whenever input I1 is NOT activated. And output relay Q2
will be energized whenever On-Delay Timer T1 is not yet

315069182/E&I/03L
timed out.
Figure 15
Output Relays: A "normal" output relay is shown here as
{Q1. Output Q1 is energized when I1 is activated, and drops
out if I1 is deactivated.
Latching output relay: remains energized indefinitely once
it has been "set", until it is "reset". Two separate coils are
used. I2 operates the "set" coil and latches the Q2 in. I3
operates the "reset" coil and causes Q2 to drop out.
Impulse or Alternating Relay: This is shown as Q3. A
pulse will latch the relay in, then a later pulse will reset it
back out. This can make a very handy alternator circuit.
To create these, move to the right column, and press OK to
create a normal {Q1 output relay. Move one digit to the left
and use the UP cursor to change to one of the other types.
Caution: any relay coil may appear only once in a circuit
diagram. You may not use the latching coil AND the normal
coil of the same relay in the same circuit diagram. This
caution applies to all types of relays, counters, timers, etc.
Figure 16
Output Relay (Q) Contacts: Q-Relays have auxiliary
contacts which can be used in any of the 3 left columns.
In this example, I1 runs Q1 and I2 runs Q2, but neither of the
outputs will activate if the other is already activated. This has
an application in a reversing contactor for example.

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Figure 17
Marker Relays: These are handy internal relays which can
be used as memory or to extend a row if more than 3 contacts
are needed such as in the ILLEGAL example shown at the
left.
The lower picture shows the correct method, using marker
relay M1.
Note that marker relays can be of various types: Normal,
Latching, and Impulse/Alternating, similar to the Q types
shown above.
Figure 18
Counter Relays: These are used to count pulses, usually
from inputs. A total is kept, visible on the parameter screen,
and when a preset total is reached, the counter's contacts will
switch over. Counters can count in either direction, plus or
minus.
Shown here in the circuit diagram, I1 pulses the CC1 counter
coil and the count is incremented by 1 for each pulse.
If I2 activates the direction coil DC1, then pulses from I1 will
count down
I3 can be used to reset the counter back to zero.
As the preset amount is reached, contact C1 activates output
relay Q1
On the parameter display, the left number (9999) is the preset
amount, and the right number (1234) is the running total. The
maximum preset is 9999, and maximum count is 9999.
The operating speed of the counters is dependant on the
complexity of the program. With a simple program they can
count up to 100 pulses per second (100 Hz).

315069182/E&I/03L
Figure 19
Timers: Shown here is a simple on-delay timer circuit and
parameter display.
Input I1 activates the TT1 timer "trigger" coil, and the time
count begins.
Input I2 activates the "reset" timer coil which will rest the
time count back down to zero, if desired.
When the preset time is elapsed, then timer contact T1 will
activate output relay Q1
The "X" in the upper-left corner of the parameter display
indicates the type of timer, in this case "on-delay". The "S"
indicates the time-units, in this case "Seconds". The number
at the top (01.14) indicates the timer has been running 1.14
seconds, and the number below it (07.00) is the preset time.
When the preset time is reached then the timer switches.
Here are the various types of timers with their parameter
symbols:
On-Delay, "X,” When the TT1 "trigger" coil is activated, the
time count begins and the timer's contacts close when the
preset time is reached and then remain closed until power is
removed from the trigger coil TT1. A momentary activation
of the reset coil RT1 will stop the timer dead and the elapsed
time will remain at zero. After the reset coil RT1 is
deactivated, the timer remains dead until the trigger coil TT1
is momentarily deactivated and then reactivated.
Off-Delay, " ": When the TT1 "trigger" coil is activated, the
timer's contacts switch on immediately. When the trigger coil
TT1 is deactivated then the time count begins and when the
time reaches the preset then the timer's contacts switch off. If
the trigger coil is reactivated while the time is running, the
time resets to zero and the time count starts again when the
trigger is deactivated again. A momentary activation of the
reset coil RT1 will stop the timer. An obvious application for
this would be a "minimum-run" function perhaps for a
pumping system, or perhaps to have a cooling fan continue
running after a motor has stopped.
Single-Pulse, " ": A single-pulse timer is the same as an off-

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delay timer except that the trigger coil TT1 need not remain
activated for the time count to proceed. A momentary pulse to
the TT1 coil will cause the time to start running, and the
contacts switch on immediately, then switch off after the time
is elapsed. The time count begins the moment the coil is
activated, even if the coil remains activated. Another pulse to
the TT1 coil while the time is already running will restart the
time count and continue running. A momentary activation of
the reset coil RT1 will stop the timer.
Flasher, " ": The flasher timer is like the "turn signal" relay
on your automobile, it blinks on and off while the trigger coil
TT1 is activated. The timer can be stopped by activating the
reset coil RT1; however it will resume blinking if the reset
coil is deactivated. One obvious application for this would be
a to control a flashing warning light.
Random On-Delay, "? X": This is identical to the normal
on-delay "X" function except that the time will be a random
number between zero and the preset time.
Random Off-Delay, "? ": This is identical to the normal off-
delay " " function except that the time will be a random
number between zero and the preset time.
Figure 20
Clock Controllers " ": Models equipped with a clock can be
used to control lighting and other functions on a regular time-
of-day and day-of-the-week schedule. There are 4 separate
clocks and each clock can have 4 programmed on/off cycles.
Each of these on/off cycles can be specified for a different
day of the week or groups of days. The clocks are not aware
of the year or
date, but they do track the day of the week. As the clocks run
continually, there is no "activation coil", one merely inserts
the clock contact " " in the diagram as needed.
In this circuit diagram Clock 1 contact " 1" controls output
relay Q1
Note there are 2 parameter screens shown, though 4 are
possible. You tell them apart by the A, B, C or D near the

315069182/E&I/03L
lower right corner. Those 4 letters are known as "channels".
In this case, Channel A turn’s clock " 1" on from 9 AM until
5 PM on weekdays, and Channel B turns clock " 1" on from
11:30 AM until 5 PM on the weekends.
Another application might be to control lights in a home
while the owner is away on vacation. Combined with the
"Random On-Delay" and "Random Off-Delay" timers shown
in the previous section, the lights will come on not at the
exact same times each day but rather at somewhat variable
times, thereby more closely simulating an occupied house.
Figure 21
Figure 22
Figure 23
Analog Comparators: The DC models are able to accept 2
analog 0-10 volt sensors. These are always connected to
inputs I7 and I8. Analog Comparator Relays are available to
process the information.
The circuit diagram in Figure 21 shows comparator A1 will
"set" output relay Q1, and comparator A2 will "reset" Q1.
The contacts can be used like any other contact, however if
the input voltage fluctuates slightly, it may be good to use
latch relays so as to prevent chattering.
There are 6 specific analog comparators to work with:
I7 >= I8: This comparator activates when the voltage on I7 is
greater than or equal to the voltage on I8. This is shown in
Fig.22, where I7 is 8.4 volts and I8 is 6.1 volts, therefore the
condition is met and comparator A1 is activated. Note the 2
numerical displays show the actual voltages present at the 2
inputs.
I7 <= I8: This comparator activates when the voltage on I7 is
less than or equal to the voltage on I8.
I7 >= set point: This comparator is activated when the
voltage on I7 is greater than or equal to a set point value. This
is shown in Fig.23, where I7 is presently 8.4 volts and the set
point is 9.3 volts, therefore the condition is not met and
comparator A2 is not activated.

315069182/E&I/03L
I7 <= set point: This comparator is activated when the
voltage on I7 is less than or equal to a set point value.
I8 >= set point: This comparator is activated when the
voltage on I8 is greater than or equal to a set point value.
I8 <= set point: This comparator is activated when the
voltage on I8 is less than or equal to a set point value.
Figure 24
Figure 25
P-Buttons: The 4 cursor buttons can be used as inputs. Here in
Fig.24, the left cursor button P1 controls output relay {Q1.
The left cursor "<" is P1
The up cursor "^" is P2
The right cursor ">" is P3
The down cursor "v" is P4.
To use these P-Buttons, one must enter the system menu and
use the "P ON" selection.
Fig.25 shows a "P" in the upper right corner, indicating that the
P-Buttons activated. See the section on SystemMenu,below.
Figure 26
"If" Jumps: The 600 series units have the ability to "jump" to
another section of the program, thereby skipping certain
portions.
Here in Fig.26, if I1 is not activated, then I2 would control
output Q1. But, if I1 were activated, then Jump relay 1 (:1)
would activate and the entire second line containing I2 would
be skipped and the program would continue at the: 1 "contact"
marker.
In all cases, I3 would still control output Q3.

315069182/E&I/03L
Figure 27
Text-Display Variables: The 600 series units are able to
display text on the screen as desired; however this can only
be entered via EASY-SOFT.
Up to 8 Text Variables (D1 thru D8) can be defined, each
of up to 12 characters. 4 lines can be displayed at any given
time.
The text display in Fig.26 shows 4 text variables telling the
operator how many pieces have been produced and how
many are required for the job's completion, and the running
condition of the machine.
Permissible displays include actual text as well as variables
such as actual values and set points of timers, counters, and
the time of day. Voltages from analog inputs I7 and I8 can
be displayed as actual voltage or as a scaled number
representing their function.
A text will be displayed whenever that Text Variable (D1
thru D8) is activated.
Figure 28
The System Screen: This is used to set system defaults and
startup behavior. To reach this screen, go to the status display by
pressing ESC several times, then press DEL and ALT at the
same time. Note: This screen is not available if a password is set
and "active", you must enter the password first and deactivate it.
See below...
Figure 29
Password Protection: Setting a system password will prevent
tampering with the program in the field and will prevent viewing
of the program by unauthorized persons.
To set a password, enter the System Menu, select
"PASSWORD", then select "CHANGE PW" and then enter a 4
digit number for your password. Then press"OK" and you may
select "ACTIVATE".
If the password appears as "----" then no password is stored.

315069182/E&I/03L
Figure 30
Figure 31
If the password appears as "XXXX" then a previous password
had been set and is stored in memory.
The password may be any number from 0001 thru 9999. Setting
a password of 0000 will completely delete a previous password.
If a password is set but not activated, then the password is stored
in memory but is not used.
If a password is set, you cannot view the program. Use the
Program menu selection from the Main Menu to enter your
password.
An active password prevents:
Changing or viewing the program.
Copying the program.
Changing System parameters.
Changing unprotected relay function parameters.
Figure 31 shows a typical parameter screen, in this case a timer.
Note the "+" in the lower right corner. This means that the
parameter screen for this particular timer is available even when
a password is active, and one may change the time values but not
the function or type. If a "-" is shown instead of a "+" then the
parameters are not viewable or changeable at all.
If a machine operator might need to change a parameter but you
wish to prevent accidental changes, then set the parameter
displays to "+" and activate a password.
If you forget your password, there is no "back door" into the
unit: Enter an incorrect password 3 times, and the program will
be deleted and the password removed and you may then put in a
new program.
Figure 32
Setting the Menu Language: The various menus can be
displayed in any of these languages: English, German, French,
Spanish or Italian. The 600 series units also have these additional
languages: Portuguese, Dutch, Swedish, Polish and Turkish.
On the System Menu, select "GB D F E I" and then select the
language desired:
GB (Great Britain) = English

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D (Deutsch) = German
F = French
E (Espanol) = Spanish
I = Italian
Figure 33
Debounce: Inputs are sometimes subject to "contact bounce"
from pushbuttons or other input devices, which may cause a
momentary "chatter" in some circuits. Setting the Debounce will
cause an input to delay activation until a "steady" signal is
received. This delay is approximately 20 milliseconds.
To activate this feature, enter the System Menu, then select
"SYSTEM" and the screen shown in Figure 33 will appear. Press
"DEBOUNCE ON" to activate.
Figure 34
Activating P-Buttons: The cursor arrow buttons on the unit can
be programmed into the circuit for use as inputs, but they must
be activated before their function will be available.
"P ON" to activate.
Figure 35
Startup Mode: The unit can be set to begin running immediately
upon power-up, or alternatively to power-up in the "stop" mode,
requiring a manual start from the Main Menu.
"MODE: RUN" to set the unit to start the program running
immediately on power-up, or press "MODE: STOP" to set the
program to NOT start on power-up.
The default is "RUN" and the programmer will likely want to
connect a start button to an input to start the machine actually
running.

315069182/E&I/03L
Figure 36
Retention: The units can be set to "retain" or "remember" the
value of various functions thru a power-down and resume
running exactly where they left off when powered-up again.
"RETENTION ON" to enable this feature.
EASY 412-DC units can remember Marker Relays M13, M14,
M15, M16, Timer T8 and Counter C8.
EASY 412-AC models do NOT offer this feature.
All 600 series units can remember Marker Relays M13, M14,
M15, M16, Timer T7, T8 and Counters C5, C6, C7 and C8 and
all 8 Text Relays
This feature is useful where a machine must remember it's exact
place in a continuing process
Memory Modules (Cards)
Figure 37
Figure 38
Notes: A small memory "Card" is available which is used to
store the program much in the way one would use a Floppy Disk.
The 412 units use the EASY-M-8K and the 600 series units use
the EASY-M-16K Memory Card. This card is a small memory
chip that plugs into a little door on the lower right face of the
unit, just above the output relay terminals.
The Card may be plugged in when the unit is powered up. The
unit must be powered up to use it's functions.
The unit will automatically detect the presence of a Card, and the
Program Menu will then have an additional choice: CARD. This
is shown in Figure 40. Select CARD and press OK and you will
see the Card Menu.
The Card Menu shown in Figure 41 has 3 options:
DEVICE->CARD copies a program from the unit to the card.
CARD->DEVICE copies a program from the card into the
unit.

315069182/E&I/03L
DELETE CARD will erase the card completely.
Units that lack the buttons and LCD Screen will automatically
load the program from the card to the unit each time the unit is
powered up.
The Memory Card provides a convenient way to update a
program and send the Card to an untrained person in the field for
installation. This way the programmer need not travel to the job-
site to make program changes.
The Memory Card is also a convenient way to archive a copy of
the program in case of damage to the unit.
Expansion Units
Figure 39
Figure 40
Expansion Units: If the requirements exceed the 12 inputs and 6
outputs of the 600 series units, it is possible to select a Master
and a Slave unit and connect them together, thereby making
available 24 inputs and 12 outputs.
The Master and Slave units can be located side-by-side or remote
from each other:
Side-By-Side Connection: Figure 39 shows a Master unit and a
Slave unit mounted side by side, connected by a small plug-
connector that is included with the Slave unit.
Remote Connection: Figure 40 shows a Master unit and a
Remote Connection Unit (EASY-200-EASY) mounted side-by-
side, connected by the included plug-connector. The Remote
Connection Unit has terminals to connect wires to the remotely
located Slave unit. The connection is made with 2 wires or a
single twisted-pair and may have a maximum length of 30
meters, approximately 100 feet. In cases where severe
interference is present, a shielded 2-wire cable should be used.
Note: Only models specifically designated as Master or Slave
can be used for expansion.

315069182/E&I/03L
Physical Wiring
Figure 41
Connecting DC Inputs: Figure 41 shows
the connection for the incoming 24 Volt
DC power and the DC operated Inputs.
Shown is a pushbutton on Input I2 and a
limit switch on Input I4. Wiring for 600
Series DC units is identical.
All Inputs (including I7 & I8) are
activated when a +24V signal appears on
the connection terminal.
Inputs I7 and I8 can also be activated by a
variable voltage signal up to +10V DC if
they are set up as "analog". Also note that
the 600 Series units with 12 inputs also
use I7 and I8 as their analog inputs.

315069182/E&I/03L
Figure 42
Connecting AC Inputs: Figure 42 shows
the connection for the incoming Line and
Neutral power at 120-240 Volts AC and
the AC operated Inputs. Shown is a
pushbutton on Input I2 and a limit switch
on Input I4. Wiring for 600 Series DC
units is identical.
AC units do not offer analog inputs.
Figure 43
Connecting Relay Outputs: Figure 43
shows Relay Output Q2 connected to
Load 1 and Relay Output Q3 connected to
Load 2.
Note that the power (shown as L & N) to
the relay outputs can be any voltage up to
250 Volts AC or DC, and they need not
all be from the same source. You may
mix L1, L2 and L3.
The Loads may be relay coils, small
motors, lights, etc.
Figure 44
Connecting Transistor Outputs: Figure
44 shows the 24 Volt DC power
connections for the outputs, and shows
Transistor Output 2 (Q2) connected to
Load 1, and Transistor Output 3 (Q3)
connected to Load 2.
The loads must all be 24 Volt DC
operated, and you must observe polarity.
Wiring for 600 Series units with transistor
outputs is identical.
Specifications:

315069182/E&I/03L
Supply Voltage
• AC Units: 90-264 Volts 50/60 Hz
• DC Units: 20.4-28.8 Volts DC
• DA Units: 10.2-15.6 Volts DC
Power Consumption
• At 115 Volts AC 50/60 Hz = 40 mA.
• At 230 Volts AC 50/60 Hz = 20 mA.
• At 24 Volts DC = 80 mA.
• Line Fuse should be minimum 1 Amp (slow-blow).
Relay Outputs
• Resistive Load = 8 amps @ 230 Volts AC 50/60 Hz
• Inductive Load (relay coils & solenoids):
o 3 Amps @ 250 Volts AC (600 switches/hour)
o 1 Amp @ 24 Volts DC (500 switches/hour)
• Filament Light Bulbs:
o 1000 Watts @ 230/240 Volts AC
o 500 Watts @ 24 Volts DC
Transistor Outputs
• Rated thermal current = 0.5 Amp @ 24 Volts DC
• Group connection rating up to 2 Amps @ 24 Volts DC
Program Capacity
• 412 Series Units: 41 lines of ladder-logic code
• 600 Series Units: 121 lines of ladder-logic code

315069182/E&I/03L
PROGRAMMABLE LOGIC CONTROLLERS
PLCs
Programmable Logic Controllers (PLCs), also referred to as programmable controllers,
are in the computer family. They are used in commercial and industrial application. A
PLC monitors inputs, makes decisions based on its program & controls the output to
automate a process or machine. This course is meant to supply you with basic
information on the function and configuration of PLCs.
WHAT IS A PLC?
A PLC is a device that was invented to replace the necessary sequential relay circuits for
machine control. The PLC works by looking at its inputs & depending upon their state,
turning on/off its outputs. The user enters a program, usually via software, that gives the
desired results.
PLCs are used in many real world applications. If there is industry present, chances are
good that there is a PLC present. If you are involved in machining, packing, material
handling, automated assembly or count less other industries you are probably already
using them. If you are not, you are wasting money & time. Almost any application that
needs some type of electrical control has need for a PLC.
For example, let’s assume that when a switch turns on we want to turn a solenoid on for
five seconds & then turn it off regardless of how long the switch is on for. We can do this
with a simple external timer. But what if the process included ten switches & solenoid?

315069182/E&I/03L
We would need ten external timers. But if the process also needed to count how many
times the switches individually turned on? We need a lot of external counters.
As you can see the bigger the process more of a need we have for a PLC. We can
simply program the PLC to count its inputs & turned the solenoid on for the specified
time.
This site gives you enough information to be able to write programs for more
complicated than the simple one above. We will take a look at what is considered to be
the top 20 PLC instructions. It can be safely estimated that what understanding of these
instructions, one can solve more than 80% of the applications in existence. That’s right,
more than 80%! Of course we’ll learn more than just these instructions to help you solve
almost all your potential PLC applications.
PLC HISTORY
In the late 1960’s PLC’s were first introduced. The primary reason for designing such a
device was eliminate the large cost involved in replacing the complicated relay based
machine control systems. Bedford Associates proposed something called a Modular
Digital Controller (MODICON) to a major US car manufacturer. Other companies at the
time proposed computer based schemes, one of which was based upon the PDP-8. The
MODICON 084 brought the world’s first PLC into commercial production.
When production requirements changed so did the control system. This becomes very
expensive when the change is frequent. Since the relay is mechanical devices they also
have a limited lifetime which required strict adhesion to maintenance schedules.
Troubleshooting was also quite tedious when so many relays are involved. Now picture a
machine control panel that included many, possibly hundreds or thousands, of individual
relays. The size could be mind boggling.
How about the complicated initial wiring of so many individual devices! These relays
would be individually wired together in a manner that would yield the desired outcome.
Where there problems? You bet! These” new controllers” also had to be easily
programmed by maintenance & plant engg. The life time had to be long & programming
changes easily performed. That’s a lot to ask!
In the mid-70’s the dominant PLC technology were sequencer state- machines & the bit-
slice based CPU. The AMD 2901 & 2903 were quite popular in MODICON & A-B
PLC’s. Conventional micro-processor lacked the power to quality solve PLC logic in all
but the smallest PLC’s. As conventional µp evolved, larger & larger PLC’s were being
based upon them. However, even today some are still based upon the 2903.
Comm. Abilities began to appear in approx. 1973. The first such system was
MADICON’s mod bus. The PLC could now talk to other PLC’s & they could be far

STUDY & ANALYSIS OF MODERN INSTRUMENTS FOR PROCESS AUTOMATION & CONTROL- 6 months study

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