Lecture Slides for the course Electronic Instrumentation-II delivered by me to Diploma in Electronics/Instrumentation Engineering.

1. BIE-601
Electronic Instrumentation-II
Unit-4
Display Devices & Recorders
Lecture-4
Mohd. Umar Rehman
umar.ee.amu@gmail.com
21. 4. 2020
BIE-601 U-4, L-4, 5 21. 4. 2020 1 / 14

2. Printers

3. Printers
When a record of readings of an instrument is required in hard
form or when the variation of a physical quantity is required, then
printers are required.
Printers can be classified as: Impact and Non-Impact type
Impact printers form characters by striking the paper with a print
head and squeezing an inked ribbon between the print head and
the paper.
Non-impact printers form characters without engaging the print
mechanism with the print surface, e.g. by heating sensitised paper
or by spraying ink from a jet.
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4. Printer Classification
Printers
Impact
Type
Daisy Wheel Dot-Matrix
Non-Impact
Type
Inkjet Thermal Laser
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5. Inkjet Printers
An ink jet printer sprays ink through nozzles onto the page.
There are two standard methods for spraying: Thermal bubble (used
by Canon and HP), and Piezoelectric (used by Epson)
Thermal inkjet printer uses heating element to heat liquid ink to
form vapor bubble, which forces the ink droplets onto the paper
through the nozzle. Most inkjet manufacturers use this technology
in consumer inkjet printers.
Instead of using heating element, piezoelectric printers use a piezo-
electric crystal in each nozzle.
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6. Thermal Bubble Jet Based Inkjet Printer
In this type of printer, the print head consists of an ink reservoir
with flexible casing, in which a certain pressure is maintained.
From this reservoir the ink gets into the droplet generation cham-
ber, provided with a nozzle into which the ink enters through cap-
illarity.
On one side of the chamber there is a heating element in the form
of a thin film.
Droplet generation is achieved by very rapidly heating up the ink,
with a few hundreds of ◦C per µs. Only a thin layer of ink that is in
direct contact with the heater will warm up, layer that gets to the
boiling temperature
This way a small amount of ink vaporizes and the additional pres-
sure generates a droplet, which is expelled through the nozzle (see
fig.)
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7. Thermal Bubble Jet Based Inkjet Printer
1. The ink is heated up, 2. the ink pressure increases, 3. the droplet is
expelled.
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8. Contd...
The heating element is then cooled down, so that the ink reduces
its volume and pressure, and the expelled ink is replaced with ink
from the reservoir.
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9. Advantages
1. Low initial Cost
2. Compact Size
3. Easy to use
4. No warm-up time required
5. Less noisy operation
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10. Disadvantages
1. High running Cost
2. Not good for high volume printing
3. Less durable
4. Output becomes blurred with time.
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11. Laser Printers
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12. Laser Printer
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13. Laser Printer
In a laser printer, a laser beam is turned ON and swept back and
forth across a photosensitive drum according to the image to be
printed.
As a result, the drum develops a static charge at certain spots where
the laser beam strikes while the other spots remain neutral.
Next, a blast of powder ink mixed with resin (toner) is applied to
the drum.
When the charged spots attract the ink powder leaving the neutral
part clean
Thus, a replica of the image is created on the drum and this image
is transferred electrostatically onto the paper by applying a reverse
field between the paper and the drum. Subsequently, the paper is
heated to fuse the toner spots on the paper.
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14. Laser Printer...Contd
The process is similar to that of xerox copiers 1 except that the light
source (Xenon flash lamp) and optical image formation arrange-
ment are necessary there.
Laser printers have resolution ranging from 6000 to 12000 DPI (dots
per inch) and are preferred for high quality printing.
Initial cost is high, while the operating cost is low.
Usually laser printers are not used for color printing.
However, color laser printers have also been developed.
Major advantage is high printing speed, effortless bulk printing
and less noisy operation.
1Infact, the laser printer was developed by scientists in Xerox Corp. USA
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15. BIE-601
Electronic Instrumentation-II
Unit-4
Display Devices & Recorders
Lecture-5
Mohd. Umar Rehman
umar.ee.amu@gmail.com
22. 4. 2020
BIE-601 U-4, L-5 22. 4. 2020 1 / 9

16. Recorders

17. XY Recorder
A recorder is an instrument which generally produces a graphical
display of the variation of a physical quantity w. r. t. time (usually).
Recorders can record both electrical and non-electrical quantities.
XY recorders accept two inputs and create a chart or graph of one
input versus the other.
They are commonly used to determine the relationship between
the two inputs. For example, in a chemical process, an XY recorder
might be used to monitor the effect temperature has on the pres-
sure of the process.
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18. Block Diagram of XY Recorder

19. XY Recorder
This system has a pen which can be positioned along the two axes
with the writing paper remaining stationary.
There are two amplifier units, one amplifier actuates the pen in the
Y-direction as the input signal is applied, while the second ampli-
fier actuates the pen in the X-direction.
The movements of the pen in X-and Y-directions are automatically
controlled by means of a motor, pulleys and a linear potentiometer.
The trace of the marking pen will be due to the combined effects of
two signals applied simultaneously.
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20. Working
Signals enter in each of the two channels, and then are attenuated
to the inherent full-scale range of the recorder (often 0.5 mA).
The signal then passes to a balance circuit where it is compared
with an internal reference voltage.
The error signal (i.e. the difference between the input signal
voltage and the reference voltage) is then used to drive a
servomotor which is used to balance the system and hold it in
balance as the value of the quantity being recorded changes.
The action described above takes place in both the axes
simultaneously. Thus, we get a record of one variable with respect
of another.
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21. XY Recorders
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22. Applications
Characteristic curves of zener diodes, rectifiers, and transistors
Stress–strain curve and hysteresis curve
Resistance versus temperature curves of various materials
Speed versus torque curves of various motors
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23. End of Unit-4