Instrumentation ( ENT 165 )
Laboratory Module
KOLEJ UNIVERSITI KEJURUTERAAN UTARA
MALAYSIA
INSTRUMENTATION
ENT 165
EXPERIMENT # 3
PRESSURE MEASUREMENT UNIT CHARACTERISTICS
NAME
PROGRAMME
signature
GROUP
DATE
MATRIK #
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Instrumentation ( ENT 165 )
Laboratory Module
Pressure Measurement Unit Characteristic
1.
OBJECTIVE
1.1 To study the principles of different types pressure measurement unit such
as:
2.
i.
Vacuum Gauge
ii.
Pressure Gauge
iii.
Differential Pressure Gauge
iv.
Inclined Tube Manometer
v.
Singe Tube Manometer
vi.
U-Tube Manometer
INTRODUCTION
Pressure is the normal force exerted by medium, usually a fluid and gas. In
engineering, pressure is most often expressed in pascal ( Pa = 1 N/m 2 ) or
pounds-force per square inch ( lbf/in2 or psi ). Often pressure is measured by
measuring its effect to deflection through use of a pressurized area and either a
gravitational or elastic restraining element. A comprehensive classification of
basic pressure-measuring methods are difficult to make. However, the
measurement unit you will observe in this session lab should suffice for our
objectives.
Vacuum Gauge
Vacuum is pressure measured below atmospheric pressure, referenced to
atmospheric pressure. Vacuum is negative gauge pressure. Because gauge
pressure is measured relative to local atmospheric pressure, it can be either
positive or negative. Perfect vacuum is zero absolute pressure and indicates
complete absence of any matter. Figure 3.1(a) shows Vacuum Gauge.
Pressure Gauge
Pressure gauge is measured relative to local ambient pressure. It’s the difference
between the measured pressure and atmospheric pressure, unless the ambient
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Instrumentation ( ENT 165 )
Laboratory Module
pressure surrounding the sensor is different from the atmospheric pressure.
Figure 3.1 (b) shows Pressure Gauge.
Differential Pressure Gauge
Differential pressure is the difference in pressure between two points of
measurement. If the pressure at one point in a system is a 150 psig and another
point is 75 psig, the differential pressure is 75 psid. The difference is usually the
lower pressure. Figure 3.1 (c) shows Differential Pressure Gauge.
U-tube Manometer
Pressures are applied to both legs of the U, and the manometer fluid is displaced
until force equilibrium is attained. Pressures P1a and P2a are transmitted to the
manometer legs through some fluid of density ρt, while the manometer fluid has
some greater density ρm. In general, a u – tube manometer will have a greater
pressure range when a more dense measuring fluid is used and greater
sensitivity ( change in height per unit change in pressure ) when a less dense
fluid is used. U-Tube Manometer can be seen in Figure 3.1 (d).
Single Tube Manometer
This is the simple method to measure pressure. Because the fluid density is
involved, accurate work will require consideration of temperature variation. Single
Tube Manometer can be seen in Figure 3.1 (e).
Inclined Tube Manometer
An Inclined Tube Manometer is used to measure very small pressures, vacuums
or differentials. The slanted scale enables reading 0.01 “wc variations, which is
impossible with conventional manometers or gauges. Inclined Tube Manometer
can be seen in Figure 3.1 (f).
The pressure which measured using above method must be compared to the
Pressure Calibrator unit. The error between the gauges reading compare to
actual reading ( Pressure Calibrator unit ) need to be calculated. This is done to
determine which measurement give the most accurate reading according to the
Pressure Calibrator unit.
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Instrumentation ( ENT 165 )
Laboratory Module
The error percentage ;
% error = Gauge value – Pressure Calibrator Value
x 100
3.1
Pressure Calibrator Value
a
b
c
d
e
f
Figure 3.1 : a)Vacuum gauge, b) Pressure Gauge, c) Differential Pressure
Gauge, d) U-tube manometer, e) Single tube manometer, f) Inclined tube
manometer
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3.
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EQUIPMENT
Figure 3.2: Assembly Diagram of Pressure Measurement Equipment
No.
1.
2.
3.
4.
5.
Item
Pressure Gauge
Vacuum Gauge
Differential Pressure Gauge
Vacuum Tank
Vacuum/Pressure Pump
4.0
PRE-LAB QUESTIONS
No.
6.
7.
8.
9.
10.
4.1 What is pressure definition ?
Item
U-Tube Manometer
Single Tube Manometer
Inclined Tube Manometer
Pressure Tank
Pressure Calibrator
( 2 marks)
4.2 Give the brief idea about the fundamental law using in pressure
measurement.
( 4 marks)
4.3 What are standard pressure commonly use in industries? State four
standards.
( 2 marks )
4.4 What medium can be used to generate pressure?
( 2 marks)
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Instrumentation ( ENT 165 )
Laboratory Module
5.0 PROCEDURE
No.
1.
Start-up procedure
Perform a quick inspection to make sure that equipment is in a proper working
condition.
2.
Be sure that all valves ( V1 to V6 ) are initially closed
3.
Ensure that the vacuum tank and pressure tank are connected to the vacuum and
pressure port of the pump, respectively (as shown in Figure 3.2).
4.
Regulate the vacuum and pressure regulator to minimum.
5.
Connect the pump power supply cable.
6.
The equipment is now ready to be run.
No.
Vacuum Gauge Calibration Procedure
1.
Perform the general start-up procedures.
2.
Connect valve V2 to the vacuum gauge connection using 5x8 mm pneumatic tubing
3.
Connect valve V1 to the ‘Lo’ port of pressure calibrator using 4x6mm pneumatic
tubing.
4.
Open all valve ( V1 to V6) about 10 second to equalize the pressure. Then close
back all valves.
5.
Open Valve V1 and V2.
6.
Ensure that the vacuum is regulated to the minimum, and then switch on the pump.
7.
Slowly adjust the vacuum regulator so that the vacuum gauge pointer indicates
exactly – 1.0 inHg.
8.
Switch on the pressure calibrator and set to inHg unit.
9.
Record the gauge and calibrator vacuum readings into the experimental data sheet
in Table 3.1.
10.
Repeat steps 6 to 8 with decreasing 1.0 inHg up to - 10.0 inHg.
11.
Always adjust the pressure and vacuum regulators to the minimum and wait until
the pressure equalizes before switch off the pump
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Instrumentation ( ENT 165 )
No.
Laboratory Module
Pressure Gauge Calibration Procedure
1.
Perform the general start-up procedures.
2.
Connect valve V5 to the pressure gauge connection using 5x8mm pneumatic tubing.
3.
Connect valve V4 to the ‘Hi’ port of pressure calibrator using 4x6mm pneumatic
tubing.
4.
Open all valve ( V1 to V6) about 10 second to equalize the pressure. Then close
back all valves.
5.
Open Valve V4 and V5.
6.
Ensure that the pressure is regulated to the minimum, and then switch on the pump.
7.
Slowly adjust the pressure regulator so that the pressure gauge pointer indicates
exactly 1 psi.
8.
Switch on the pressure calibrator and set to psi unit.
9.
Record the gauge and calibrator pressure readings into the experimental data sheet
in Table 3.2.
10.
Repeat steps 6 to 8 with increasing 1 psi up to 10 psi.
11.
Always adjust the pressure and vacuum regulators to the minimum and wait until the
pressure equalizes before switch off the pump
No.
Differential Pressure Gauge Calibration Procedure
1.
Perform the general start-up procedures.
2.
Connect valve V5 to the ‘Hi’ port of the differential pressure gauge using 5x8mm
pneumatic tubing.
Connect valve V2 to the ‘Lo’ port of the differential pressure gauge using 5x8mm
pneumatic tubing.
3.
4.
Connect valves V1 and V4 to the ‘Lo’ and ‘Hi’ port of pressure calibrator, respectively
using 4x6mm pneumatic tubing.
5.
Open all valve ( V1 to V6) about 10 second to equalize the pressure. Then close back
all valves.
6.
Open Valve V1, V2, V4, and V5.
7.
Ensure that the pressure and vacuum is regulated to the minimum, and then switch on
the pump.
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Laboratory Module
8.
Slowly adjust the pressure regulator so that the gauge pointer indicates 1 psi.
9.
Switch on the pressure calibrator and set to psi unit.
10.
Record the gauge and calibrator pressure readings into the experimental data sheet in
Table 3.3.
11.
Repeat steps 7 to 9 with increasing 1.0 psi up to 10 psi.
12.
Always adjust the pressure and vacuum regulators to the minimum and wait until the
pressure equalizes before switch off the pump
No.
Inclined Tube Manometer Calibration Procedure
1.
Perform the general start-up procedures.
2.
Connect valve V5 to the ‘Hi’ port of the inclined manometer using 8mm grey pneumatic
tubing.
Note: Leave the ‘Lo’ port of the inclined tube manometer opened to the atmospheric
pressure.
3.
Connect valve V4 to the ‘Hi’ port of pressure calibrator using 6mm pneumatic tubing.
4.
Open all valve ( V1 to V6) about 10 second to equalize the pressure. Then close back
all valves.
5.
Open Valve V4, V5 and V6.
Note: V6 is opened to reduce pressure due to small range of the inclined tube
manometer.
6.
Adjust manometer ruler so that the red fluid on the zero scale.
7.
Ensure that the pressure is regulated to the minimum, and then switch on the pump.
8.
Switch on the pressure calibrator and set to inH2O unit
9.
Slowly adjust the pressure regulator and V6 so that the indication liquid shows 0.4
inH2O.
10.
Record the manometer and calibrator pressure readings into the experimental data
sheet in Table 3.4.
11.
Repeat steps 9 to 10 with increasing 0.2 inH2O up to 2.6 inH2O.
11.
Always adjust the pressure and vacuum regulators to the minimum and wait until the
pressure equalizes before switch off the pump
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Instrumentation ( ENT 165 )
No.
Laboratory Module
Single Tube Manometer Calibration Procedure
1.
Perform the general start-up procedures.
2.
Connect valve V5 to the ‘Hi’ port of the Single Tube Manometer using 8mm grey
tubing.
3.
Connect valve V4 to the ‘Hi’ port of pressure calibrator using 6mm pneumatic tubing.
4.
Open all valve ( V1 to V6) about 10 second to equalize the pressure. Then close back
all valves.
5.
Open Valve V4, V5 and V6.
Note: V6 is opened to reduce pressure due to small range of the Single Tube
Manometer.
6.
Ensure that the pressure is regulated to the minimum, and then switch on the pump.
7.
Slowly adjust the pressure regulator so that the indication liquid shows 0.2 kPa.
8.
Switch on the pressure calibrator and set to kPa unit.
9.
Record the manometer and calibrator pressure readings into the experimental data
sheet in Table 3.5.
10.
Repeat steps 6 to 8 with increasing 0.2 kPa up to 2.0 kPa.
11.
Always adjust the pressure and vacuum regulators to the minimum and wait until the
pressure equalizes before switch off the pump.
No.
U-Tube Manometer Calibration Procedure
1.
Perform the general start-up procedures.
2.
Connect valve V5 to the ‘Hi’ port of the U-tube manometer using 6x8mm pneumatic
tubing.
3.
Connect valve V2 to the ‘Lo’ port of the U-tube manometer using 6x8mm pneumatic
tubing.
4.
Connect valves V1 and V4 to the ‘Lo’ and ‘Hi’ port of pressure calibrator, respectively
using 4x6mm pneumatic tubing.
5.
Open all valve ( V1 to V6) about 10 second to equalize the pressure. Then close back
all valves.
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Instrumentation ( ENT 165 )
Laboratory Module
6.
Open Valve V1, V2, V4, and V5.
7.
Ensure that the pressure and vacuum is regulated to the minimum, and then switch on
the pump.
8.
Slowly adjust the pressure regulator so that the liquid in Left tube shows 220 mmH 2O
height.
9.
Switch on the manometer calibrator and set to mH2O unit.
10.
Record the gauge (Left and Right tube) and calibrator pressure readings into the
experimental data sheet in Table 3.6.
11.
Repeat steps 7 to 9 with left tube showing 240, 260, 280……400 mmH2O.
12.
Always adjust the pressure and vacuum regulators to the minimum and wait until the
pressure equalizes before switch off the pump.
No.
Shut-down Procedure
1.
Disconnect all pneumatic tubings that connect gauges or manometers to tank.
2.
Check that the pressure/vacuum regulators are set to minimum.
3.
Switch off the pump and the main power.
4.
End of experiment
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Instrumentation ( ENT 165 )
Laboratory Module
6.0 RESULT
Observation Table
Table 3.1: Vacuum Gauge
Gauge reading
Actual reading
( inHg)
( inHg)
%Error
-1.0
-2.0
-3.0
-4.0
-5.0
-6.0
-7.0
-8.0
-9.0
-10.0
* Plot the graph gauge reading against actual reading. Label the graph.
Table 3.2 : Pressure Gauge
Gauge reading
Actual reading
( psi)
( psi)
%Error
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
* Plot the graph gauge reading against actual reading. Label the graph.
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Instrumentation ( ENT 165 )
Laboratory Module
Table 3.3 : Differential Pressure Gauge
Gauge reading
Actual reading
( psi)
( psi)
%Error
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
* Plot the graph gauge reading against actual reading. Label the graph.
Table 3.4 : InclinedTube Manometer
Manometer reading
Actual reading
( inH2O)
( inH2O)
%Error
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
* Plot the graph gauge reading against actual reading. Label the graph.
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Instrumentation ( ENT 165 )
Laboratory Module
Table 3.5 : Single Tube Manometer
Manometer reading
Actual reading
( kPa)
( kPa)
%Error
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
* Plot the graph gauge reading against actual reading. Label the graph.
Table 3.6 : U-Tube Manometer
Manometer
Actual reading
difference reading
( mmH2O)
%Error
( mmH2O)
220
240
260
280
300
320
340
360
380
400
* Plot the graph gauge reading against actual reading. Label the graph.
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Instrumentation ( ENT 165 )
7.0
Laboratory Module
DISCUSSION
7.1
Explain the characteristic of each measurement unit that you had
observed in lab session:
a) Parts and their function.
b) Operation of measurement unit
c) Advantages
d) Disadvantages
7.2
( 20 marks )
Discuss the differences between Vacuum gauges, Pressure gauges and
Differential Pressure gauges.
7.3
( 10 marks )
Suggest any transducers you know that suitable to replace the Vacuum
gauges, Pressure gauges and Differential Pressure Gauges in this lab
session. Explain the transducer’s characteristic.
7.4
( 15 marks )
Base on the graph that you have plotted, is that every gauge and
manometer need to be calibrated again? Why?( Give any references that say so).
( 10 marks )
7.5
Suggest any method to reduce the error in measuring the pressure in this
lab session.
8.0
( 5 marks )
CONCLUSION ( 5 marks )
(Based on data discussion, make your overall conclusion by referring to experiment objectives)
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