Mercury-Containing Thermometer Alternatives

This six minute video by the National Institute of Standards and Technology (NIST) describes the types of mercury-containing thermometer alternatives that are currently available for use today in laboratory and industrial applications. This video and the similar ones on the EPA website ( are important adjuncts to the recently announced Calibration Policy change at NIST, NIST will cease offering calibration services for mercury-filled thermometers on March 1, 2011. … Continue reading

Calibrating Ordinary Thermometers

This six-minute video by AquaLab captures the correct way to check, verify and if necessary, adjust some ordinary thermometers using an ice bath. Most people think that it’s easier to do so at the boiling point of water, but the ice point (very nearly 0.01 ° C at all normal atmospheric pressures) is far more stable than the boiling point that varies considerably with atmospheric pressure and consequently the altitude of the location at which the measurement is made. What’s more, the ice point was, until about 1990, the fundamental reference point for the Centigrade and Fahrenheit scales. However, when … Continue reading

Triple Point Cell at 36.324 Degrees Celcius

About a unique Triple Point Cell based on Ethylene Carbonate  developed at Britain’s National Physical Laboratory (NPL) in a nearly 4 minute video from YouTube. It’s kind of a commercial, but a really useful one. It explains about this special calibration tool and how it can and is being used to help verify the calibration of sensors designed to measure human body temperature. … Continue reading

How to Realize a Triple Point of Water Cell

From Fluke Corporation In this video Matt Newman from Fluke Corporation’s Hart Scientific Division ( demonstrates the proper technique for realizing a triple point of water cell for temperature calibration. Triple point of water cells are used for calibrating a variety of precision thermometers. The triple point of water cell is an intrinsic standard with a temperature defined to be 0.010 °C. This temperature is the most important temperature of the International Temperature Scale of 1990 (ITS-90) which is used to define the Kelvin unit of thermodynamic temperature on the International System of Units (SI). For more YouTube videos from … Continue reading

Triple Point Cells (part one)

Explanation of Triple Point Cells with Dr R. L. Rusby of Britain’s National Physical Laboratory (NPL) in a nearly 10 minute video from YouTube. This is the first in a series of several excellent videos online that deal with this fundamental calibration point in establishing and reproducing practical calibrations. The meaning of the triple point of matter is explained very well, with several examples, on Wikipedia at: and the triple point of water is perhaps most succinctly described in the IUPAC * “Gold Book“** at: illustrating the pressure-temperature conceptional relationship of the states of matter, in general, showing  … Continue reading

As Found Calibration Data

This free, online technical paper from Burns Engineering discusses why the resistance at the triple point of water (RTPW) is considered the most important piece of information obtained during calibration of a Secondary Standard Platinum Resistance Thermometers (SSPRT). It goes further, telling how the change in the RTPW can be used to estimate changes at other temperatures. They also have a second related paper on their website, entitled Using an Ice Bath to Approximate the Triple Point of Water. This paper describes two methods for approximating the TPW resistance measurement of a SSPRT using an ice bath and provides a … Continue reading