Maintenance and Validation of Liquid-in-Glass Thermometers
Christina D. Cross, Dean C. Ripple, Gregory F. Strouse
Liquid-in-glass thermometers are pervasive in use throughout industry and provide a convenient method for measuring temperature over for a broad range of applications with reasonable stability and accuracy. However, liquid-in-glass thermometers are subject to drift and change in calibration status as a function of time and use of temperature. This paper describes a method for the calibration and recalibration of liquid-in-glass thermometers based on use at temperature. Procedures and examples are given for visually inspecting the thermometer to approve its use, determining the calibration status of the thermometer, guidance on recalibration of a thermometer, realization and use of an ice point for a single-point recalibration, and the determination of uncertainties in correcting a calibrated thermometer. Additionally, recommendations for recalibration intervals based on frequency of use and maximum temperature measured are give.