How to choose the right laboratory thermometer?

Accurate thermometric testing and documentation of a given sample - or determining ambient temperature and humidity - is often an integral part of accurate materials testing. So, determine which field/lab thermometer is right for your specific materials testing needs. This blog post helps remove heat from the process and provides insight into liquid-in-glass (LiG) mercury thermometers, non-mercury LiG thermometers, and digital thermometers. It also provides information on the limits of mercury LiG thermometers, including those for laboratory and industrial use, and finally, considerations for determining which thermometer meets your needs.

ASTM Mercury Thermometers for Materials Testing

Mercury thermometers used to be one of the common types of LiG thermometers , touted for their high accuracy and ability to measure extreme temperature ranges.

However, for at least the past two decades, many state, local and federal agencies have classified mercury as a toxic substance, many of which have phased out and banned its use in thermometers and other devices. The sale and shipment of mercury instruments is often regulated and sometimes banned in specific regions. The National Institute of Standards and Technology (NIST) stopped calibrating mercury thermometers in 2011, and non-mercury alternatives have also begun to grow in terms of utilization and technological advancement.

However, certain laboratory test methods still specify the use of mercury thermometers in certain applications. The American Standard Test Method for Density of Semi-Solid and Solid Asphalt Materials (ASTM) D3289 Standard Test Method (Nickel Crucible Method), revised last September, is an example. However, the standard also states that "any other temperature measuring device with equivalent accuracy may be used."

Currently, ASTM Standard D1856 / AASHTO Standard R59 for the Abson method for the recovery of asphalt binder from solution still requires a 7C or 7F thermometer - and there is no LiG essential oil substitute. But keep in mind that there may be other state standards that rely on mercury thermometers for specific tests.

At Gilson, we provide each mercury thermometer with a safety data sheet listing the standards they meet in the product description and in the specifications for each product. In addition, we comply with all regulations restricting the sale and shipment of such products.

State listings for product bans and phase-outs are available online at the Northeast Waste Management Officials Association/Interstate Mercury Education and Reduction Clearinghouse. Due to new and ongoing restrictions on the use, sale, and shipping of mercury, we strongly recommend that anyone considering purchasing a mercury thermometer check their city and state regulations before ordering.

Alternatives to Mercury Thermometers (ASTM Non-Mercury Thermometers)

With the growing ban on mercury products across the United States, there is a need for alternative products to measure and record temperature in laboratories and the materials testing industry. Additionally, state and federal agencies have strong incentives to revise standards to effectively align with testing for mercury-free materials. ASTM, AASHTO, and state agencies that maintain such standards continue to research and standardize non-mercury alternatives that are safer to use, provide precisely accurate temperature values, and can be reliably calibrated.

These less hazardous LiG thermometers can have their own set of considerations. For example, according to aashtoresource.org, may respond to temperature changes differently than mercury, and may have different thermal expansion characteristics than mercury. While some mercury-free LiG thermometers contain a harmless indicating substance, others may use petroleum, which is a hazardous substance. The indicating fluid used with Gilson ASTM and ASTM equivalent mercury-free thermometers is biodegradable, non-toxic and non-hazardous. Again, Gilson has safety data sheets for all of our non-mercury thermometers online along with product descriptions and specifications.

The Environmental Protection Agency (EPA) provides some information resources on alternative temperature measuring devices, as well as a list of the revised ASTM standards for testing with mercury-free thermometers.

Digital thermometers for laboratory and field materials testing

Like any other digital technology, digital thermometers offer new advances in their design and materials that LiG thermometers do not offer. They do more than measure and display temperature. Many can record maximum and minimum temperatures, record time-stamped data and interface with a computer or laptop to analyze the data in more detail. Obviously, the more complex the technology, the higher the price.

Likewise, there are good digital thermometers on the market for a lot more and a lot less. Digital temperature measurement devices can be calibrated; in fact, some are self-calibrating. Choices include platinum resistance thermometers and resistance thermal Detectors; platinum is said to be a desirable element for measuring temperature. A clear LCD display provides good resolution for temperature readings, and units come in a variety of shapes and sizes for easy measurement in any environment. A guide to what you should know about digital thermometers is available at aashtoresource.org.

Like LiG Mercury-Free Thermometers, their digital thermometers are reliable, accurate, and accurate, and meet the requirements of various standard test methods as an alternative to mercury temperature measurement. Plus, since the digital thermometer contains no harmful ingredients, there are no sales or use restrictions. Product descriptions and specifications for the digital units available from Gilson are published on the product page.

Here are some factors to determine which thermometer is right for you: