ASTM E77 Inspection and Verification of Thermometers

Scope:

ASTM E77 is crucial to ensure that thermometers used indicate temperatures within the maximum scale and are compatible with the apparatus and the purpose for which they are designed. The procedures are also used for other liquid-in-glass thermometers.

Procedure

In ASTM E77, first gas bubbles are detected and removed readily. Compliance is determined with lineal dimensional specifications by comparing the thermometer with the appropriate scale or template. For compliance with specifications, the errors in the temperature indications of ASTM thermometers are being verified.

Video 01: Calibration of a thermometer

Specimen size:

Most thermometers contain mercury as the actuating liquid. Some thermometers use an organic liquid, especially those at temperatures below −56 °C (−69 °F). The partial-immersion thermometers range from approximately 0.3 °C (0.5 °F) to 2.0 °C (3.0 °F).

Data

The following equation is used in ASTM E77 to calculate corrections:

Emergent stem correction = kn (T- t)

where:

k = differential expansion coefficient of the liquid and the glass of which the thermometer is made

n = number of degrees emergent from the bath,

T = temperature of the bath, and

t = average temperature of the liquid column of n degrees.

Conclusion:

ASTM E77 is crucial to ensure that thermometers used indicate temperatures within the maximum scale and are compatible with the apparatus and the purpose for which they are designed.