1. Principles of Measurement
LESSON 1
Principles of Measurement
Let the Games Begin!

2. Objectives Measurement of temperature and pressure
Units of measurement
Measurement devices

3. References Introduction to Naval Engineering
Principles of Naval Engineering

4. Purpose of Measuring Devices
Why essential to proper operation of propulsion plants?

5. WHAT IS TEMPERATURE?
An indication of the internal energy contained in a substance
Mono-Atomic Gases: Linearly proportional
Poly-Atomic Gases: translational, rotational and vibrational kinetic energy.
Temp is a measure of but not directly proportional to internal kinetic energy.

6. Measurement of Temperature
Relative Scales
Fahrenheit (°F)
Celsius (°C)
Absolute Scales
Rankine (°R)
Kelvin (K)
F = 1.8 C R = F C = (F - 32) / K = C Temperature At the beginning of the renaissance many scientists recognized that the idea of the subjective sense of temperature needed to be quantified. They knew that the behavior, and sometimes the structure, of a body changed as it became hotter or colder. The most vivid example of the phenomenon is the behavior and structure of water as it is cooled to the freezing point. But, how does one quantify, or measure, a subjective feeling?
Galileo, and others, tried to build various types of thermometers which were are successful to some extent, but they all lacked the essential quality of being able to measure temperature with any more repeatability than the common sense of touch.
Along comes a German Physicist, Gabriel Fahrenheit, and the mercury thermometer. Fahrenheit's real contribution was a sealed thermometer that measured the expansion and contraction of mercury with temperature changes and it was independent of atmospheric pressure changes. The susceptibility of the non-sealed thermometers to atmospheric pressure changes later evolved into the barometer that is the basis of the next topic.Fahrenheit. He needed to calibrate his thermometer at some repeatable temperatures and so he selected the two most common and universally repeatable temperatures: the freezing point of pure water and the boiling point of pure water.Fahrenheit engraved a scale on his prototype thermometer before he calibrated it. When he measure the temperatures of ice water and boiling water, he came up with two of the most inconvenient numbers around: 32° and 212°.

7. Temperature Relationships
(°F) = 9/5*(°C) +32
(°C) = 5/9*[(°F) –32]
(°F) = (°R) –
(°C) = (K) –

8. Measurement of Pressure
Definition: Force per unit area
Units of measurement
Pounds force per square inch (psi)
Inches Hg or inches H2O (“Hg)
Atmospheres (atm)

9. Pressure Relationships
Gage pressure (PSIG)
Absolute pressure (PSIA)
Vacuum pressure (PSIV) or (in Hg)
Atmospheric pressure (14.7 psi)

10. Pressure Relationships
Absolute Pressure = Atmospheric Press Gage Press.
Vacuum = Atmospheric Pressure - Absolute Pressure

11. Pressure Relationships
30 PSIA
15.3 PSIG
GAGE
PRESSURE
(PSIG)
ABSOLUTE
PRESSURE
(PSIA)
Atmospheric Pressure
14.7 PSIA
0 PSIG
(Average at Sea Level)
0 In. Hg
VACUUM
(in. Hg)
0 PSIA
29.92 In. Hg

12. Sensors
In the late 1800s, another physicist, Bill Rankine, measured the change in thermal energy with each change in temperature for many substances and he found that each of these substances had the same theoretical temperature at which they possessed no thermal energy. That temperature is approximately -460° F.
Rankine called this point absolute zero and declared the only true temperature scale to be the Rankine scale which started at absolute zero.
Celsius was a little smarter than Fahrenheit when he calibrated his thermometer. He waited until after he “calibrated” his thermometer in ice water and boiling water to put the scale markings on his thermometer. He made his lower calibration point zero degrees and his upper calibration point 100 degrees. While dividing the temperature scale into 100 increments made more sense over the range of temperatures experienced in everyday life, his scale, like that of Fahrenheit, did not start at absolute zero. Kelvin fixed Celsius in the same manner as Rankine fixed Fahrenheit in that a degree Kelvin is the same as a degree Celsius except that zero degrees Kelvin is at degrees Celsius.

13. Principle of Operation Temperature Devices
Expansion Thermometers
Liquid in glass
Bimetallic
Filled system/distant reading
Pyrometers
Thermocouple
Resistance
Radiation and optical pyrometers

14. Expansion Thermometer
Liquid in Glass
Bimetallic
Filled System/Distant Reading

15. Expansion Thermometer
Liquid in Glass
Bimetallic
Filled System/Distant Reading

16. Expansion Thermometer
Liquid in Glass
Bimetallic
Filled System/Distant Reading

17. Expansion Thermometer
Liquid in Glass
Bimetallic
Filled System/Distant Reading

18. Pyrometers
Thermocouple
Resistance
Radiation and Optical

19. Pyrometers
Thermocouple
Resistance
Radiation and Optical

20. Pyrometers
Thermocouple
Resistance
Radiation and Optical

21. Pyrometers
Thermocouple
Resistance
Radiation and Optical

22. Operation of Pressure Measuring Devices
Manometers
Bourdon tube
Bellows gage

23. Operation of Pressure Measuring Devices
Manometers
Bourdon tube
Bellows gage

24. Operation of Pressure Measuring Devices
Manometers
Bourdon tube
Bellows gage

25. Operation of Pressure Measuring Devices
Manometers
Bourdon tube
Bellows gage

26. Questions?