The third article of our Infrared thermometers series Explain how to properly validate the accuracy of an infrared device on the ground. Our first article examined the emissivity and how to obtain a precise reading, while the second focused on how to clean and store an infrared thermometer. If you have not already done so, we also recommend that you read these articles in order to fully understand the operation of the infrared before trying a calibration.
Calibration vs validation
The calibration process of a thermometer can only be carried out in a controlled laboratory environment. The validation process, where an instrument is compared to verify its precision, is what is described here. If the reading of an instrument turns out to be inaccurate during validation using a calibrated thermometer, it must then be sent to a laboratory to be repaired or re-standard.
Why the validation of a temperature on an IR instrument is different from the calibration of a penetration probe
Infrared thermometers only measure surface temperatures and therefore should only be used as a quick guide. Indeed, the precision of the measurement is affected by many factors and variables such as the surface emissivity, the type of material, transparency, color and reflectivity (read our complete guide to obtain precise infrared readings here ). An infrared thermometer must be validated compared to a calibrated "master" thermometer in the laboratory on a known temperature source. The best way to control the emissivity and the temperature of a surface, ensuring that you get the real reading of an infrared thermometer is to use a solid black body. This minimizes most external factors and prevents temperature from changing too quickly.
Emissivity
As we saw in our previous blog article On the details and limits of the infrared, emissivity plays a huge role during the calibration of IR thermometers.
Depending on what you point your infrared thermometer, you will get a variation in the infrared energy emitted. Esstyivity is a measure of the capacity of a material to emit infrared energy. It is measured on a scale of approximately 0.01 to 1.00. Generally, the more the emissivity index of a material is close to 1.00, the more this material tends to absorb reflected or ambient infrared energy and only emits its own infrared radiation. Click here To find out more about emissivity.
What equipment is necessary to validate the accuracy of an infrared instrument?
At Thermometre.fr, we are able to provide a traceable calibration certificate on all infrared thermometers.
In order to check the accuracy of an infrared thermometer on the ground, a Thermometers comparator and a high -precision calibrated "master" thermometer, such as a Reference thermometer , are necessary. The thermometer comparator consists of an aluminum cup with a solid matt black base. The base integrates two holes to take the internal temperature of the base using a "master" thermometer. An infrared thermometer can then be held above the cup input to take the temperature of the base surface.
How to validate a temperature on an infrared instrument?
Make sure the infrared comparator and thermometer are clean and free from any debris or substance that can affect reading (read our complete guide on cleaning and storing your IR device here ).
Place the thermometer comparison on a flat surface.
Insert the reference thermometer probe in one of the base test holes and let it stabilize. This can take any duration, depending on the response time of the inserted probe.
If the infrared device has adjustable emissivity, make sure it is set to 0.95, the correct adjustment for the matt black surface of the thermometer comparator.
Direct the thermometer down of the comparator and take a measure. The instrument must read less than 1 ° C of the reference thermometer to an ambient room temperature of 22 ° C, depending on the precision of the thermometer.
At what temperature can an infrared instrument be validated?
The accuracy of an infrared thermometer can be checked using a comparison at any stable temperature. However, to reduce the possibility of a temperature difference between the inner surface and the basic test hole, it is more precise at 22 ° C, room temperature of the room.
Thermal stability
The use of an infrared thermometer at hot or cold temperatures will increase the possibility of thermal instability.
For each 1 ° C of the upper environment or less than 22 ° C (room temperature), an adjustment factor must be added to the accuracy of the instrument to take into account thermal instability. These are generally 0.05 ° C for Raytemp thermometers. Other infrared thermometers can have a different value. Here is a table indicating the values to be taken into account when using a Raytemp 2 thermometer in cold or hot environments.
*The precision and thermal stability of other instruments may vary.
To do and not to do
Stretch At an ambient temperature of around 22 ° C if possible.
Born Do not change the temperature surrounding the comparator before validation or the surface temperature may differ from the internal temperature.
Be Aware of external factors that influence the correct IR reading of the comparator, such as humidity, frost and debris.
Born Do not position the infrared thermometer too far, or at an angle, when taking the comparator's temperature as it can provide inaccurate reading.
Make Measures as quickly as possible to prevent the surface temperature from changing.
Don't forget that thermometers need time to acclimatize to a different environment.
