LESSON 2. CALIBRATION AND USE OF TEMPERATURE STANDARDS
ACCP Subcourse Number MM 0483........
Thermometry
Lesson Objectives..................................
After studying this lesson you should have
a basic knowledge of the standards used to
calibrate temperature sensing devices. Be
able to answer all review questions
correctly pertaining to:
1. Platinum resistance thermometer.
2. Equiphase triple point of water cell.
3. Ice point calibration standard.
4. Constant temperature Baths.
5. Thermocouple.
6. Resistance thermometer.
7. Temperature measurement system.
Credit Hours.......................................... Two hours
1. CALIBRATION REFERENCES
a. Primary Standards.
The primary standards are the platinum resistance thermometer and platinum-platinum
rhodium (10) thermocouple.
The platinum resistance thermometers cover a range of -182.970,C to 630.5, C and are
calibrated against the following references:
Boiling point of oxygen........... -182.970,C
Triple point of water............. 0.01000,C
Freezing point of antimony........ 630.5,C
The triple point of water is also called the equiphase of water, because at 0.01000, C,
water coexists as liquid, solid, and gas (vapor). This is the most accurate temperature
reference at present.
The freezing point of a substance is the temperature at which a liquid when cooled
becomes a solid. Boiling point, however, is the temperature at which a liquid becomes a
gas.
Calibration of the platinum-platinum rhodium (10) thermocouple, which is the
international standard from 630.5,C to 1, 063,C, is referenced to the freezing points of
antimony ( 630.5,C) and gold (1, 063,C) .
b. TEMPERATURE STANDARDS AND THE TRIPLE POINT OF WATER.
Fixed points which define international temperature scales are thermal states or
temperatures uniquely defined and recognized by physical phenomena occurring
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