TIPS ON IR MEASUREMENT
How to get the IR thermometer to show the right temperature
IR measurement is a useful and effective measurement method in various situations in most industries. There are many advantages to non-contact temperature measurement. It is quick, can be done from a safe distance and you do not risk affecting or destroying what is being measured. However, there are some things to consider in order to measure correctly and get reliable temperature values. Here are some useful tips to help you succeed.
Where and how should I measure?
In general, an IR thermometer can be used to measure the temperature of all kinds of non-metallic materials and painted metal surfaces. In the case of tarnished or oxidized metal surfaces, measurement results can be misleading due to the fact that the emission factor (see “Measure with the correct emission factor” below) can vary from 0.3 to 0.9. If you just want to make a comparative measurement and absolute accuracy is not so important, you can measure with an IR thermometer.
However, in cases where you are looking for higher accuracy, we suggest that you make a comparative contact measurement and correct the emission factor. Alternatively, paint or tape the surface of the material to be measured. The latter measures are recommended for IR measurement of high gloss surfaces.
Common sources of error.
Do you suspect that the IR meter is showing the wrong temperature? Here are some common reasons why you may get wrong values:
- The IR thermometer has the wrong emission factor set. Read more below!
- The reflection from the shiny metal surface interferes with the measurement.
- The measuring spot is larger than the measuring object.
- There is dirt or fog on the lens.
- The temperature difference between instrument and ambient air is too great.
- It is an air pocket between the packaging material and the measured object.
Measure with the correct emission factor.
The emission factor is something that many people either don’t know or forget about when making an IR measurement. So what is the emission factor? In short, it can be described as a value of the radiant heat emitted by a particular material. In order to make an accurate temperature measurement, the IR thermometer must be corrected and set to a specific emission value between 0.01 and 0.99. The vast majority of IR devices have a pre-set emission factor of 0.95. It provides good accuracy for measurements below 100 plus degrees on materials such as paper, plaster, wood, rubber, stone, paint and food.
Follow these steps to check and set the emission factor:
- Turn on the instrument by pressing the “trigger”.
- Press the up arrow for three seconds to display the set emission factor.
- Press the up or down arrow to change the emission factor. The instrument automatically returns to measurement mode after three seconds.
The above example applies to Testo’s 830-T1, 830-T2 and 830-T4 IR thermometers. If you have another meter, check the user manual for how to set the emission factor.
Use tape on shiny surfaces.
The IR measurement of shiny surfaces requires either painting or taping the surface. The easiest way is to temporarily use a piece of tape. We have a special tape with a fixed emission factor, designed specifically for IR measurement of high-gloss surfaces. Attach the tape and let it acclimatize for a little while – then just measure. Here you can read about and buy our issue tape.
Applications for IR measurement.
Here are some examples of times when it is useful to have an IR thermometer on hand to measure temperature quickly and easily.
Emission table for some common materials.
| Material | Temperatur | E |
| Aluminium, blankvalsat | 170 °C | 0,04 |
| Betong | 25 °C | 0.93 |
| Is, slät | 0 °C | 0.97 |
| Vatten | 20 °C | 0,96 |
| Järn, polerat | 20 °C | 0.24 |
| Järn med valsbeläggning | 20 °C | 0.77 |
| Gips | 20 °C | 0.90 |
| Glas | 90 °C | 0.94 |
| Gummi, hårt | 23 °C | 0.94 |
| Trä | 70 °C | 0.94 |
| Kylfläns, svarteloxerad | 50 °C | 0.98 |
| Koppar, något matt | 20 °C | 0.04 |
| Koppar, oxiderad | 130 °C | 0.76 |
| Plast (PE, PP, PVC) | 20 °C | 0.94 |
| Mässing, oxiderad | 200 °C | 0.61 |
| Papper | 20 °C | 0.97 |
| Porslin | 20 °C | 0.92 |
| Svartfärg (matt) | 80 °C | 0.97 |
| Stål, oxiderad | 200 °C | 0.79 |
| Lera, bränd | 70 °C | 0.91 |
| Tegelsten, murbruk, puts | 20 °C | 0.93 |
If you want to learn more about IR technology, read our fact sheet Measuring with IR thermometers.
