06 chapter06 binary_logic_systems_Rev02

Binary Logic Systems
Chapter 06 – Binary Logic Systems
EMEC125

Why Binary Logic Systems?
• Documents need to be understood by people with very different
backgrounds. People who could need the documentation are:
• Management
• Process Designers
• Operations Staffs
• Maintenance Technicians
• Electrical and Control System Professionals
• Logic Device Programmers
• Supervisory Control and Data Acquisition (SCADA) System Configurators

Binary Logic Diagrams
• ISA-5.2-1976 (R1992) Binary Logic
Diagrams for Process Operations and
Scientific Apparatus Makers Association
(SAMA) PMC 22.1 Functional
Diagramming of Instrument and Control
Systems. Both address binary logic
diagrams.
• Elements of these standard are now
included in ANSI/ISA-5.1

Terms You Should Know Before Proceeding
• Discrete Control
• “On/off control. One of the two output values is equal to zero.” (International
Society of Automation, 2003, p. 150)
• A better definition would be: A signal that is either fully ON or fully OFF with
no values in-between.
• Binary
• “1. A term applied to a signal or device that has only two discrete positions or
states. When used in its simplest form, as in “binary signal” (as opposed to
“analog signal”), the term denotes an “on-off” or “high-low” state, that is, one
that does not represent continuously varying quantities. [ANSI-ISA-5.1-1984
(R1992)].” (International Society of Automation, 2003, p. 49).

• Analog
• “1. Having the form of continuously variable physical quantities, as in data.
Contrast with digital. 2. The representation of numerical quantities by means
of physical variables, such as translation, rotation, voltage or resistance. 3. A
waveform is analog if it is continuous and varies over an arbitrary range.
Contrast with digital.” (International Society of Automation, 2003, p. 21).
• Another way to define Analog is: A continually varying signal that can be fully
ON, fully OFF or any level in between. (International Society of Automation,
2003, p. 21).

• Process Variable
• “1. Any variable property of a process. The term process variable is used in
the relevant standard to apply to all variables other than instrument signals
[ANSI/ISA-5.1-1984 (R1992)]. 2. In the treatment of material, any
characteristic or measurable attribute whose value changes with changes in
prevailing conditions. Common variables are flow, level, pressure and
temperature.” (International Society of Automation, 2003, p. 392).
• Control Variable (Controlled Variable)
• “1. The variable that the control system attempts to keep at the set point
value. The set point may be constant or variable. 2. The part of a process to
be controlled (flow, level, temperature, pressure, etc.).” (International Society
of Automation, 2003, p. 109).

Combining Analog and On-Off Control
• Combining analog and on/off control schemes can be defined by
using:
• Process control descriptions
• Instrument diagrams
• Functional diagrams
• Electrical schematic diagrams
• These documents can be used independently or together depending
upon the phase of design, construction or operation.

Process Control Descriptions
• The more complex the process, the more detail that is required in a
Process Control Description. The following are areas to be included,
but not limited to, in a Process Description:
• Process Description
• Title of the system
• General description
• Form
• Control Description
• More specific data on how the system will perform
• Loop-by-loop descriptions
• Format

The Binary Concept – Multiple Input
• This two-state binary concept, applied to gates, can be the basis for
making decisions in ladder logic.
• The gate is a device that has one or more inputs and one output.
• The gate will perform a logical decision based on the status of its
inputs and produce a result at its one output.

Using Gates to Make Decisions
• The logical AND gate or function.
• All inputs must be true to obtain an output.
AND
Gate
Air Conditioner
Switch
Blower Switch
Cold Air
The automotive air conditioning to work,
the Air Conditioner must be turned on and
the Blower must be turned on.

Using Gates to Make Decisions
• The logical OR gate or function.
• Any one input must be true to obtain an output.
OR
Gate
Passenger
Door Switch
Driver Door
Switch
Dome Light
The automotive dome light will be on when
the passenger door OR the driver door or
both door switch(s) is activated.

The AND Function
• The AND function has two or more
inputs and one output. The input
signals are labeled A, B, C, etc. and
the output signal is labeled Y.
• A binary 1 represents the presence
of a voltage (signal). A binary 0
represents the absence of voltage
(no signal, 0 V or ground).
• Logic functions can be represented
using a truth table. The truth table
lists all possible input status
conditions with the corresponding
output status for each set of input
condition.
AND
Gate
A
B
YInputs
Output
Two input AND gate

An AND Gate Application
• An AND gate functions like switches in series.
• The light will only be ON when switch A AND switch B are both
closed.
AND
Gate
PB1 = 1
LT1 ON
PB2 = 1

The OR Function
• The OR function has two or more
inputs and one output. The input
signals are labeled A, B, C, etc. and
the output signal is labeled Y.
• A binary 1 represents the presence
of a voltage (signal). A binary 0
represents the absence of voltage
(no signal, 0 V or ground).
• Logic functions can be represented
using a truth table. The truth table
lists all possible input status
conditions with the corresponding
output status for each set of input
condition.
OR
Gate
A
B
YInputs
Output
Two input OR gate

An OR Gate Application
• An OR gate functions like switches in parallel.
• The light will be ON when either or both switch A OR switch B are
closed.
OR
Gate
PB3 = 1
PB4 = 0
LT2 ON

The NOT Function (Inverter)
• The NOT function gate, also
called an inverter, has one input
and one output.
• The NOT gate functions like its
name states, it inverts the input
signal status.
• If the input is a 1 the output is a
0.
• If the input is a 0, the output is a
1.
Input Input
A A
(not A)

A NOT Gate Application
• The NOT gate functions like a normally closed switch.
• The light will be ON if the switch is NOT being activated and OFF
when the switch IS being activated.
Input Input
PB5 PB5
(not PB5)

The NAND Function
• The NAND gate functions like an
AND gate with an INVERTER on
its output.
• The only time that the output of
a NAND gate is a 0 is when all
the inputs are a binary 1.
NAND
Gate
PB6
PB7
Light
Two input NAND gate

The NOR Function
• The NOR gate functions like an
OR gate with an INVERTER on its
output.
• The only time that the output of
a NOR gate is a 1 is when all the
inputs are a binary 0.
NOR
Gate
PB8
PB9
LT5
Two input NOR gate

The XOR (Exclusive- OR) Function
• The XOR gate has two inputs and
one output.
• The output of this gate is a 1
when the two inputs are
opposite to each other.
Therefore, one input a 1 and the
other a 0.
• The output of this gate is a 0
when both inputs are the same,
either two 0’s or two 1’s.
XOR
Gate
PB10
PB11
LT6

AND Gate Circuits
AND
Gate
LS10
LS10A
SOL010Inputs
Output
Two input AND gate
Electromechanical Ladder Diagram
PLC/PAC Ladder Diagram

OR Gate Circuits
OR
Gate
LS011
LS012
Sol011Inputs
Output
Two input OR gate

Combinations of Gates
OR
Gate AND
Gate
LS013
LS014 LT013
Inputs
Output
CR

Combination of Gates
AND
Gate
OR
Gate
OR
Gate
LS015
LS016
LT016Inputs
Output
CR01
CR02

AND
Gate
OR
Gate
LS017
LS031
AH017
Inputs Output
LS018

AND
Gate
OR
Gate
AND
Gate
PB019
PB020
LT019Inputs
Output
PB021
PB022

Why is this
instruction
programmed open?
AND
Gate
CR6
LS021
SOL021
Inputs Output
CR6

Why are these
instruction
programmed open?
This is an XOR circuit

AND
Gate
OR
Gate
A
B
M
Inputs
Output
C
D
Draw the PLC/PAC
ladder diagram
for this logic

Control Description (From ANSI/ISA-5.1)
• Control system design for:
• Small volumes for long and short periods should allow tank to fill to a high level to
automatically start the pump and then to stop the pump at a low level.
• Large volumes for long periods should allow the pump t run continuously and
maintain a fixed level with a level-to-flow cascade control loop.
• Pump (run, or operation) control is selected by a three-position Hand-Off-
Auto (H-O-A) selector switch:
• Selector switch is in “HAND” position.
• Selector switch is in “AUTO” position.
• Pump should be stopped at any time:
• Automatically if low level is exceeded.
• By operation the stop pushbutton.
• Switching the H-O-A selector to “OFF” position.
ISA 5.1 (2009).pdf

Instrument Diagram
T-1
LT
*02
LSL
*02
HS
*02-B
HS
*01
HS
*02-A
LSH
*02
FT
*01
P-1
FO
FIC
*01
LIC
*02
FV
*01
STOP
START
H-O-A

Functional Diagram Symbols
(*)
 Measuring, Input, or Readout Device
 [*] = Instrument Tag Number
 Symbols from Table 5.5 in the ANSI/ISA-
5.1-2009 Standard
(*)
(*)
 Automatic single-mode controller
(*)
(*) (*)
 Automatic two-mode controller
(*)  Automatic single controller
(*)  Manual signal processor
(*)  Final control element
 Control valve
(*)
 Final control element with positioner
 Control valve with positioner

Binary Logic – AND & OR Gates
A
N
D
OR
A
B
C
A
B
C
Y Y
A
B
A
B Y
AND
OR
A B C Y
0 0 0 0
0 0 1 0
0 1 0 0
0 1 1 0
1 0 0 0
1 0 1 0
1 1 0 0
1 1 1 1
A B C Y
0 0 0 0
0 0 1 1
0 1 0 1
0 1 1 1
1 0 0 1
1 0 1 1
1 1 0 1
1 1 1 1
A
N
D
OR
A
B
C
A
B
C
Y Y
A
B
C
A
B
C
Y

Binary Logic – NOT & Memory
A
A
B
C
NOT A A A
S
R D
NOT
Memory
A
A
B
C
NOT A A A
S
R D
A A
0 1
1 0
A B C D
1 0 0 0 1
2 1 0 1 0
3 0 0 1 0
4 0 1 0 1
5 0 0 0 1
6 1 1 1 0
7 0 0 1 0
8 1 1 0 1

Electrical Schematic – Ladder Diagram
M1
M2
LSH*02
HS*02-A
HS*02-B LSL*02
M
OL
STOP
START
H
O
A

Logic Diagram Example
STARTSTOP COIL OVERLOAD
RELAY CONTACTS
Pump
Stop
Motor Starter,
Pump Motor
Overload
Motor Starter,
Reset Pump
Motor
NOT
S
R
NOT
A
N
D
Pump
Start
Pump
Starts
Electrical
Logic

Function Block Diagram – Allen Bradley (FYI)

Function Block Diagram – Siemens (FYI)

Δ
P I
Δ
P I
TA TA A
T
A
(*)f(x)
FT
*01
LT
*02
FV*01
H
LSH*02
L
LSL*02
A
N
D
A
N
D
HS
*02-B
STOP
NOT
A
N
DHS
*02-A
HS
*01 H-O-A
A
N
D
A
N
D
OR
S
Ro
S
Ro
OL
OL
PUMP
P-1
START
H
A
‘1’ when
NOT at
Low Level
‘1’ when
at High
Level
This diagram literally
sucks – SU QU E
Functional Diagram

Δ
P I
Δ
P I
TA TA A
T
A
(*)f(x)
FT
*01
LT
*02
FV*01
H
LSH*02
L
LSL*02
‘1’ when
NOT at
Low Level
‘1’ when
at High
Level
HS
*02-B
STOP
HS
*02-A
START
HS
*01 H-O-A
H
A
M2
M1
OL
Pump
Functional Diagram

Summary
• This chapter discussed discrete control (on/off control) in a process
plant.
• Logic diagrams will aid in the understanding of how Safety
Instrumented Systems (SIS) work.
• Functional diagram symbols were discussed along with an example of
how they are used.
• Basic logic gates have been discussed, along with the symbols used to
represent them.

References
CEmark.com & European.Authorized-Representative.eu. (1996-2015). What is CE Marking (CE Mark)?
Retrieved June 17, 2015, from Welkang Tech Consulting: http://www.ce-marking.org/what-is-ce-
marking.html
International Society of Automation. (2003). Automation, Systems, and Instrumentation Dictonary (4th ed.).
Research Triangle Park: International Society of Automation. Retrieved from
http://app.knovel.com/hotlink/toc/id:kpASIDE005/automation-systems-instrumentation/automation-
systems-instrumentation
International Society of Automation. (2009, September 18). ANSI/ISA-5.1-2009 Instrumentation Symbols and
Identification. American National Standard. Research Triangle Park, North Carolina: International Society
of Automation.
Kirk, W. F., Weedon, A. T., & Kirk, P. (2014). Instrumentation and Process Control (6th ed.). Orland Park,
Illinois: American Technical Publishers.
Lipták, G. B. (Ed.). (1995). Process Measurement and Analysis (3rd ed.). Radnor, Pennsylvania: Chilton Book
Company.
McAvinew, T., & Mulley, R. (2004). Control System Documentation Applying Symbols and Identification (2nd
ed.). Research Triangle Park, North Carolina, USA: International Society of Automation.
Meier, F. A., & Meier, A. C. (2011). Instrumentation and Control Systems Documentation (2nd ed.). Research
Triangle Park, North Carolina: International Society of Automation.
Thomas, E. C. (2015). Introduction to Process Technology (4th ed.). Boston, MA: Cengage Learning.

06 chapter06 binary_logic_systems_Rev02

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