Cooling

Integral Thermal Protection

Care should be taken to ensure that the camera does not overheat, as this can cause system failure. Overheating may occur if either of the following situations arises:

Air-cooled Models

  • The air vents on the sides of the head are accidentally blocked

  • The ambient air temperature is more than 30ºC (ZL41 Cell 5.5), or 27ºC (ZL41 Cell 4.2)

To protect the camera from overheating, a thermal switch has been attached to the heat sink. If the temperature of the heat sink rises above predefined limit then the current supply to the cooler will cut out and a buzzer will sound. To reset this, it is necessary to exit the software and switch off the camera, correct the issue, let the system cool then restart the camera and software.

Water-cooled Models

• The coolant system is not operating correctly

To protect the camera from overheating, a thermal switch has been attached to the heat sink. If the temperature of the heat rises above predefined limit then a buzzer will sound. To reset this, it is necessary to exit the software and switch off the camera, correct the issue, let the system cool then restart the camera and software.

TE Cooling (Air-Cooled Models)

The ZL41 Cell sCMOS sensor is cooled using a thermoelectric (TE) cooler. TE coolers are small, electrically powered devices with no moving parts, making them reliable and convenient. A TE cooler is actually a heat pump, i.e. it achieves a temperature difference by transferring heat from its ‘cold side’ (the CMOS-chip) to its ‘hot side’ (the built-in heat sink). Therefore the minimum absolute operating temperature of the ZL41 Cell sensor depends on the temperature of the heat sink. The maximum temperature difference that a TE device can attain is dependent on the following factors:

  • Heat load created by the ZL41 Cell sensor (dependant on pixel readout speed)

  • Number of cooling stages of the TE cooler

  • Operating current

  • Hot side temperature of thermoelectric cooler

Even with a fan, a heat sink typically needs to be at least 10ºC hotter than the air (room) temperature to transfer heat efficiently to the surrounding air. Therefore during normal operation the temperature of the heatsink within the camera head will be warmer than the ambient (room) temperature.

TE Cooling (Water Cooled Models)

For water cooled models the dissipation of heat from the TE cooler is achieved by circulating coolant liquid through the heat sink. The high specific heat capacity of water provides efficient heat dissipation, allowing the sensor to be operated at -10ºC. Benefits of water cooling include:

  1. Reduced vibration as there is no cooling fan required, which may be useful for ultra-sensitive measurements and

  2. Improved dark current.