Measuring Temperature Accurately: What Are the Costs? (Part I)

For a few hundred years, mercury-in-glass thermometers were the precise method for measuring temperature. Since German physicist Daniel Gabriel Fahrenheit invented them in 1714, the liquid was the expected element in thermometers, which were the most common instrument for temperature measurement. The phrase “when the mercury rises” references the use of mercury thermometers to gauge temperature.

Yet, mercury is a neurotoxin and can affect vision, mood, and the central nervous system. As a toxic metal, even small amounts can impact the physical and cognitive functioning of the body. As early as 2004, the Environmental Protection agency (EPA) prohibited the sale and distribution of mercury fever thermometers in certain states and by 2008 called for the phase-out of all mercury-containing non-fever thermometers used in EPA labs. Mercury use has since continued to decline. According to the National Institute of Standards and Technology (NIST), professional groups and organizations globally are phasing out mercury thermometers. In fact, NIST stopped calibrating mercury thermometers in March of 2011.

As mercury-in-glass thermometers were replaced with alternatives, such as spirit-filled thermometers and other temperature measurement instruments including thermistors and thermocouples, the question remains how accurate are the alternatives? What is the best option for a particular application? How much does accuracy cost?