Mapúa University

Muralla St. Intramuros, Manila

School Of Mechanical, Manufacturing, and Energy Engineering

MECHANICAL ENGINEERING LABORATORY 1

EXPERIMENT NO. 2
PRESSURE AND TEMPERATURE MEASURING DEVICES

PANGILINAN, NIKKO L. Date of Performance: 09/09/2024

ME139L-3 / B5 Date of Submission: 09/16/2024
GROUP 2

SCORE

Engr. Jose Luis L. Villalon

Instructor

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 TABLE OF CONTENTS
OBJECTIVES 3
THEORY/HYPOTHESIS 3
LIST OF APPARATUS 5
PROCEDURE 6
SETUP OF APPARATUS 7
FINAL DATA SHEET 9
SAMPLE COMPUTATION
TEST DATA ANALYSIS
QUESTIONS WITH ANSWERS
CONCLUSION
RECOMMENDATION
REFERENCES

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 TITLE: PRESSURE AND TEMPERATURE MEASURING DEVICES
OBJECTIVES:
 To be able to learn how to calibrate using bourdon dead weight gage
tester.
 To be able to learn how to calibrate thermometers with known melting
and freezing points.
 To familiarize oneself with the different types of pressure and
temperature measuring devices.

THEORY/HYPOTHESIS:
PRESSURE
Since pressure is defined as force per unit area, it is apparent that
measurements of pressure and force are virtually the same thing. Measurements of
pressure are accomplished by balancing the pressure to be measured against a
known force. In barometers, manometers, and dead-weight testers, the pressure is
balanced against the force of gravity acting on a measured column of liquid or a
known weight. In bourdon and other spring gages, the known force is produced by
the deflection of a calibrated spring.
In most engineering measurements the force is expressed in pounds and the
area in square inches (psi). But the terms pressure and head are often used
interchangeably, as when the ventilating engineers speaks of a “static pressure of 2
in. of water” in a fan duct or the meteorologist refers to a “barometric pressure of 29
in.” (of mercury).
Pressures are measured either from a datum of absolute zero or from
atmospheric pressure. The term vacuum refers to a pressure measured downward
from the atmospheric line; hence when the barometer reads 30 in., the equivalent of
a “vacuum of 10 in. mercury’ is an absolute pressure of 20 in. of mercury.
Higher pressures are commonly measured by balancing the pressure against
the resistance of a metal spring. Deflection then becomes a measure of pressure,
but of course this device must be calibrated.
The ASME Test Codes recommend that a mercury barometer should always
be used. In many cases, pressures less than atmospheric are given in inches of
mercury, vacuum. In such cases, the vacuum recorded is the read on the scale of a
mercury column.
In the bourdon gage the spring is a flattened tube, bent to form a circular arc.
When subjected to internal pressure the tube will tend to straighten out. The fixed
end of tube is connected to the pressure source, and the free end is sealed and
connected to a multiplying and indicating mechanism, from which the pressure is
read. The common pressure ranges for full-scale readings of bourdon gages are 15
to 10,000 psi, but higher ranges are also available. Vacuum gages of the same type
are calibrated in inches of mercury and compound gages are marked in pounds per
square inch above the atmosphere and inches of mercury below atmosphere.

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 Dead-weight pressure gages are devices by which exact values of fluid
pressure may be produced through the use of standard weight acting vertically on a
frictionless piston of known area. Dead-weight gages are also used for precise
measurement and control of important pressures, such as the operating steam
pressure in a large electric central station.
A dead-weight tester and standard weights are to be used as the calibration
standard for pressures above atmosphere. For vacuum-gage calibration, an
arrangement is made for direct comparison with a mercury manometer. Water and
mercury manometers may also be used for calibrations in the range 0 to 15 psig, and
a hook-gage manometer or other vertical micro-manometer is used for calibration of
gages reading less than 5 in. of water.
TEMPERATURE
Three general types of instruments are commonly used for measuring
temperatures below the incandescent range, viz., expansion thermometers,
resistance thermometers, and thermocouples. Accurate temperature measurements
are not easy to make, but the difficulties are more often due to wrong methods of
installation and use than to the instruments themselves.
ASME Tests of Temperature-measuring Instrument and Apparatus, under
many of the conditions met in power tests the desired accuracy in the measurement
of temperature can be obtained only by observance of suitable precautions in the
installation and use of temperature-measuring instruments, and in the interpretation
of the results obtained with them.
Many of the instruments available for temperature measurements are capable
of indicating temperature far more accurately than is required in most tests. The
difficulties in the use of the instruments are due either to wrong installation or to
careless use.
Three methods are readily available for checking thermometers and
thermocouples. The apparatus required is as follows:
1. Comparison with Standard instruments. A thermometer – comparison bath
with mechanical stirrer should be provided, and the instruments immersed in
closed proximity in the bath of water or oil. For high temperatures a bath of
molten salt or an electric muffle furnace can be used. The accuracy of the
comparison standard must be certified, preferably by a Bureau of Standards
calibration. Stem-emergence corrections must be carefully determined for the
thermometers.

2. Checking by Reference to Known Boiling or Melting Points – Suitable

beakers, crucibles, and heat sources are required, depending on the materials
used and on the temperature range. For the boiling point of water, a total-
immersion steam bath is preferred.

3. Checking by Reference to Saturated-steam Temperatures – this method is

successful only when a dead-weight platform or other very accurate method

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 of measuring the steam pressure is available. True temperatures are read
from steam tables.

LIST OF APPARATUS/REAGENT

Bourdon Set of
Tester
Pressure Measurement Standard
Weights
Dead Weight
Tester

Hydraulic Oil

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Temperature Measurement

Analog Digital Graduated

Thermometer Thermometer Cylinder
Steam
PROCEDURE Bath

A. Calibration of Bourdon Gage by Dead Weight Tester

1. Loosen the screw of the hand-wheel by turning it counterclockwise and
remove the valve that covers the oil reservoir.
2. Pour the hydraulic oil into the reservoir up to its proper level then close the
valve cover.
3. To eliminate or remove the air that is trapped inside the cylinder, open the
drain level and screw the hand-wheel slowly by turning it clockwise. In this
way, the air bubbles will spill out through the drain cock.
4. Lock the drain valve.
5. Spin the rotating plunger to minimize the friction and slowly screw the
hand-wheel counterclockwise until the platform reaches the starting point.
6. For trial 1, slowly turn the screws of the platform and the plunger rises
(floating freely) to approximately 1 inch above the starting point.
7. Record the gage reading.
8. For the succeeding trials, load the platform gradually with the standard
weight specified by the instruction and provided by the data sheet.

9. Record the gage readings for each weight added.

10. Calculate the percentage difference between the gage to be calibrated and
the tester.

B. Checking by Reference to Known Boiling or Melting Points

a. For Melting point
1. Place ice into the graduated cylinder.
2. Placed the mercury thermometer into the cylinder and lower the
thermometer until the bulb is still near the bottom.
3. Leaving the ice to melt, the temperature of the thermometer should
be read. There will come a point when the thermometer is stable.
Record this temperature as the melting point.

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 b. For Boiling point
1. Place a fair amount of water on the steam bath.
2. Place the thermometer in the steam bath through the desired
location.
3. Turn on the apparatus to start the test.
4. There will come a point when the water will begin to boil. Read the
thermometer and record the result as the boiling point reading of
the thermometer and the digital counter.
SETUP OF APPARATUS
1. Bourdon Gage

2. Water bath

3. Ice Melting point

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FINAL DATA SHEET

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