The technical data of industrial cameras always refer to the permissible operating temperature or ambient temperature. This is the air temperature that prevails around the device at a certain distance. Typically, the lower limit of the temperature range is just above 0 °C, as condensation on and in the camera, which is not normally protected against water, must be avoided. The upper limit represents the worst-case limit to be on the safe side. A thermometer in the room can be used to measure whether the temperature is suitable or not. It's not quite that simple - this document shows other points on the subject that can be taken into account.

Camera manufacturers usually specify the ambient temperature as follows:

• Storage temperature -20...60 °C, relative humidity 20...90%

• Ambient temperature 0...45 °C, relative humidity 30...80%

However, it becomes more difficult when the extremes are reached. It must be noted that cameras differ in terms of power consumption, for example. This leads to different housing temperatures. The design of the camera itself can also be different. Housing temperatures can be reduced by connecting to heat-dissipating metal structures. Another effective way of reducing housing temperatures is convection cooling through air movement, which can also be "forced" by fans. The housing temperature indicates how warm it is inside the camera. There are normally two critical temperature limits here:

• The image sensor and

• the FPGA/memory or "glue logic".

Industrial image sensors, for example, are limited to 75 °C (again: ambient temperature: Sony CMOS) during operation; sensors in the automotive sector can have higher limits. FPGA/memory & glue logic in the industrial sector have a limit of 85 °C.

Balluff GmbH offers an extended temperature range option for some cameras, which allows a wider temperature range and has been explicitly tested for this. This option may be sufficient for many users, but is associated with a surcharge.

If you want to test the temperature limits of a camera, industrial cameras from Balluff offer two integrated thermometers that can be read out via GigE Vision properties. One is located directly next to the image sensor, the other is located near the FPGA. As long as the thermometers remain within the permissible limits, the camera can be operated safely, regardless of the environment. The thermometers can be read out via GigE Vision properties.

Figure 1: Device Temperature Selector

The following setup shows a BVS CA-SF1 and its temperature on a desk at 23 °C room temperature. The ambient temperature could rise another 27 °C without the need for additional cooling (the temperature on the sensor board could also be checked, depending on what is relevant).

Figure 2: Surface temperature

The camera consumes ~2.5 W, so the thermal resistance of the housing camera can be calculated as RTh ~10 K/W. It is possible to operate the camera below 0 °C (down to -20 °C) as long as condensation on and inside the camera can be avoided. There is a difference of approx. 10 °C between the housing temperature at the front flange (red measuring point) and the value read out at the sensor, as is the case here with a BVS CA-SF2.

If the camera is connected to a heat spreader, the thermal resistance can be significantly reduced (through heat conduction and convection): (the temperature was measured at the same point).

Figure 3: Surface temperature with heat dissipation

The tests showed that the upper limit of the housing temperature corresponds to 65 °C. This can be used as an alternative to the specification for the permissible ambient temperature. Board-level cameras, on the other hand, are more sensitive as there is no housing for heat dissipation.