If you work with temperature measurement instruments, it’s important to achieve a certain level of accuracy and precision. Calibration ensures that you can rely on the accuracy of instruments over and over again.
Understanding uncertainty levels
Rather than claiming that an instrument is 100% accurate, which is never really possible, instrument calibration focuses on uncertainty levels. Uncertainty levels are the maximum expected error in any measurement using that instrument. In some situations, this is referred to as an instrument being ‘out of tolerance’ when it doesn’t meet certain accuracy standards.
When calibrating precision instruments such as thermometers, it is first important to understand the different levels of uncertainty that may be permissible. This generally depends on what you’re using the instruments for, and the permitted level of inaccuracy for that particular use.
There are typically three common levels of uncertainty:
- +/- 1 degree Celsius
- +/- 0.1 degree Celsius
- +/- 0.01 degree Celsius
As an example, your standard household thermometer may work on a permissible uncertainty level of +/- 1 degree Celsius, whereas a permissible uncertainty level of +/- 0.01 degree Celsius is used for master reference thermometers and other such precision devices.
Temperature instrument calibration basics
While the process of correctly calibrating instruments is a lot more complex than this, we’re going to discuss the basic approach to keeping measurement instruments in correct calibration.
Comparison: The simplest way to check an instrument’s accuracy is to compare it with a master reference thermometer. Naturally, reference thermometers themselves are expertly calibrated to an uncertainty level of +/- 0.01 degree Celsius, meaning in simple terms that they are very accurate.
Using conditions as close as possible to the instrument’s normal operating environment, it can be compared with a master reference thermometer to check the accuracy levels. Because your reference thermometer is already calibrated to a very low level of uncertainty, if the device being calibrated matches the reference, it is considered to be accurate.
Master reference thermometers: Of course, for the above basic approach to work, you need absolute confidence in the reference instrument. The process of calibration for these is quite involved. The best option for this type of instrument calibration is to always have instruments checked, tested and calibrated by a NATA-accredited testing service.
These reference thermometers should be periodically calibrated by a professional testing service to ensure their ongoing accuracy.
Why is calibration important for temperature measurement devices?
It doesn’t matter what industry you operate in, because temperature accuracy plays a part in so many situations. From scientific research and medical laboratories to the food production industry, temperature is important. Essentially, only the permissible uncertainty levels change, and that’s because all instruments have a different designated use.
All testing should seek to imitate the instrument’s normal operating environment. When temperature measurement equipment is outside the normal permitted levels of error, the consequences can be severe. For example, public swimming pools may be too hot. Drink manufacturing could be compromised by not operating at the right temperature. Laboratory results could be inaccurate in scientific testing. The list goes on and on, so it’s crucial in any industry relying on temperature control that your measurement instruments are properly calibrated.
If you’d like to discuss the calibration of your temperature measurement instruments or master reference thermometers, NWI Group is here to help. Contact us today to find out more.
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