Temperature Calibration

Temperature calibration refers to the calibration of any device used in a system that measures temperature. Most importantly, this usually means the temperature sensor, itself, which is typically a platinum resistance thermometer (PRT or PT-100), thermistor, or thermocouple. Readings from these thermometers are made by “thermometer readout” devices which measure their electrical outputs and convert them to temperature according to the International Temperature Scale of 1990 (ITS-90)

International Temperature Scale of 1990 »

Thermometers are typically calibrated by placing them in a stable temperature environment (heat source) and comparing their output to that of a calibrated “reference thermometer” or “standard thermometer.” Fluke Calibration provides three general categories of heat sources:  industrial heat sources (dry-well calibrators, Micro-Baths, etc.) for field use; fluid baths and thermocouple furnaces for laboratory use; and fixed-point cells for “primary” calibrations.  Fluke Calibration also offers a variety of reference thermometers, including SPRTs, and thermometer readout instruments.

In addition, Fluke Calibration provides a variety of laboratory and field solutions for calibrating the electronics used in temperature measurement circuits.

Field, laboratory, and primary temperature calibration

Field temperature calibration(or “industrial” or “portable” temperature calibration) applies to thermometers being tested outside of a laboratory environment, typically to accuracies ranging from 5 °C to 0.5 °C. Dry-wells, Metrology Wells, Micro-Baths, IR targets, and other portable heat sources provide stable temperatures, while portable thermometer readouts and thermometer standards can provide reference temperatures beyond that available directly from the heat source.

Laboratory or secondary temperature calibration relates to the calibration of reference-grade PRT or PT-100, precision thermistors, and noble-metal thermocouples. Ultra-stable and uniform temperature baths and horizontal furnaces (for the high temperatures needed by thermocouples) are used along with SPRT reference thermometers and high-accuracy thermometer readouts.  Such systems can provide calibration accuracies from 0.5 °C to 0.02 °C.

Fixed-point or primary temperature calibration utilizes fixed-point cells, such as the Triple Point of Water, which provide extremely accurate and repeatable temperature when they are properly “realized,” typically in a laboratory setting. Such systems are used for calibrating SPRTs and noble-metal thermocouples and can be as accurate as 0.001 °C. 

Hart Scientific products and the Fluke Calibration brand

In 2001, Fluke acquired Hart Scientific, located in American Fork, Utah. Temperature products continued to be sold under the Hart Scientific label until 2010 when Fluke introduced the Fluke Calibration brand, which includes the Hart Scientific products as well as electrical, RF, pressure, and flow calibration products. Today, some temperature products are manufactured at Fluke headquarters in Everett, Washington, while fixed-point and thermometry products continue to be manufactured in Utah.  We continue to rely on the exceptional team of experts that previously made Hart Scientific the world’s leading brand for temperature calibration.

Related reference materials

Understanding Temperature Calibration Uncertainties »
Automating Temperature Calibrations »
Fluke Calibration’s Scope of Accreditation for Temperature Calibrations »
Establishment of a Primary Standards Laboratory »
Establishment of a Secondary Laboratory »
Infrared Temperature Calibration 101 »

Calibrating a temperature sensor can be a challenge, but is very doable with some know-how and the right products. The first step is to understand the thermometer being calibrated:  What type of electrical signal does it output or is it entirely mechanical? What are its physical characteristics (size, shape, size and shape of sensor hidden inside the probe sheath, etc.)? Over what temperature range is it used? And what accuracies are relied on over those temperatures? Can it be calibrated in a laboratory or must it be calibrated in the field or even in-situ?

The answers to these questions help define the products and processes that comprise the right solution for you. One quick and easy way to work through these answers and define a calibration solution that is fully reliable but not overdone is to contact our application experts at 1.877.883.8225.  They have a great deal of knowledge and experience adapting calibration solutions to a wide variety of requirements.

If you have a general idea of what you’re looking for, but want to find just the right product(s) to meet your need, these selection guides provide a quick way to compare our various product offerings and provide links to take you directly to complete information about each product.

Product Selection Guides

Primary standards

Thermometer readouts

Thermometer probes

Constant temperature calibration baths

Industrial temperature calibrators

Related reference materials

Temperature calibration: Tips and tricks from the real world