Avoiding measurement errors – Tips for correct measurement
Immersion and penetration measurement
In immersion and penetration measurements, the temperature probe is inserted directly into the measurement object. The measurement is finished as soon as the t99 time is reached.
The most common measurement errors
If the temperature probe is colder than the measurement object, then energy in the form of heat is withdrawn from the measurement object in the vicinity of the probe. If it is warmer than the measurement object, then heat is introduced to the object. The mass ratio of the probe and the medium should also be taken into account: The greater this is, the more energy is withdrawn from the measurement object. Since this energy withdrawal means that the actual temperature of the object is no longer measured, a too high mass of the probe can lead to measurement errors.
Tips for correct penetration measurement
- The penetration or immersion depth should be the 10 to 15 times the diameter of the probe.
- For immersion measurements in liquids, the liquid should be kept constantly in motion.
- In the ideal case, t99 is reached after approx. 0.5 seconds.
In surface measurements, the probe head is placed vertically onto the surface.
Here it is important to ensure that neither the contact surface of the probe head, nor the the measurement object, are uneven, as this can falsify the measurement.
Tips for measuring surface temperature
- Place probe tip flat onto surface.
- Do not move the probe during the measurement.
- Apply constant and sufficient pressure.
- Use low-mass surface probe.
- In the ideal case, t99 is reached after approx. 3 seconds.
Measurement of air temperature
For measurement of moving air, the measurement probe is simply introduced to the environment to be measured. In order to achieve a short acclimatization time, ideally use an air probe with an exposed sensor. The measurement result can be optimized by moving the probe in the air at 2 m/s during the measurement.
Tips for measuring air temperature
- Use air probe with exposed sensor (not penetration or surface probes).
- Move the probe at 2 m/s during the measurement.
- Hold the probe away from your body.
- Use radiation-protected probes.
- In the ideal case, t99 is reached after approx. 7 seconds.