The recommended temperature range for all Ophir power/energy sensors and meters is as follows:
- Operating: 15 – 35 °C
- Storage: 0 – 50 °C This guideline applies to both sensors and meters.
Regarding meters, temperature effects are very small. One can expect a variation in calibration of the meter of < ±1% over the temperature range 10°C to 60°C.
Thermal sensors. The sensitivity to stable ambient temperatures is similarly small, since these sensors actually measure temperature gradient across the thermopile junctions. Calibration may vary < ±1% over the temperature range from 10°C to 50°C.
At very low temperatures, one also needs to consider possible condensation of moisture on the absorber, which could affect readings.
At high temperatures, one should be aware that the maximum rated power is lower than that given in the specification (which is for room temperature), since the sensor body will have a harder time dissipating heat in an already hot environment. Some numbers are given in our web site FAQ section.
Changing temperature, on the other hand, is a different story. Thermal sensors measure heat flow, after all, and an ambient temperature that is changing by as little as 1°C / minute can cause a change in the reading.
The following are examples of situations in which this may happen:
- Part of the laser beam is incident on the sensor body (this heats the sensor body and can cause unwanted heat flow inside the sensor, which might affect the measurement)
- A sensor that has been brought from a warm location to a cooler one (it should first be allowed to reach thermal equilibrium with its new environment before beginning measurement)
- Sudden change in the temperature, or flow rate, of cooling water in a water-cooled sensor
Pyroelectric Sensors: Our new Pyro-C energy sensors have built-in temperature compensation and so temperature effects are negligible. For our legacy line of pyro sensors, there is a positive sensitivity coefficient of approximately 0.2% / °C.
Photodiode Sensors: Since these are semiconductor devices, they have a sensitivity coefficient with temperature and wavelength based on the detector material. The following graph shows the effect details: