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Chapter 7 Troubleshooting 69
69
Cooling Troubleshooting
Temperature Lock Cannot be Achieved or Maintained.
Operating a PI-SCX:1300 camera with coolant at a temperature colder than specified
could cause induced condensation in the electronics enclosure and possible catastrophic
damage to the camera. Damage resulting from this type of operation may void the
warranty.
Possible causes could include:
Ambient temperature greater than +23°C. If it is greater than +23°C, you will need to
cool the camera environment or raise the set temperature.
The vacuum has deteriorated and needs to be refreshed.
The connectors of the cable that interconnects the controller and the camera need to
be secured.
The target array temperature is not appropriate for your particular camera and CCD
array.
For cameras that are liquid-cooled or have liquid-assisted cooling, the coolant flow
rate may be insufficient due to a pinched coolant line, blockages, circulator power
problem, or pump failure. Check the flow rate and coolant temperature.
For a TE-cooled camera, the camera's internal temperature may be too high, such as
might occur if the operating environment is particularly warm or if you are
attempting to operate at a temperature colder than the specified limit. TE-cooled
cameras are equipped with a thermal-protection switch that shuts the cooler circuits
down if the internal temperature exceeds a preset limit. Typically, camera operation
is restored automatically in about ten minutes. Although the thermo-protection switch
will protect the camera, you are nevertheless advised to power down and correct the
operating conditions that caused the thermal-overload to occur.
Camera loses Temperature Lock
The internal temperature of the camera is too high. This might occur if the operating
environment is particularly warm or if you are trying to operate at a temperature colder
than the specified limit. If this happens, an internal thermal overload switch will disable
the cooler circuits to protect them. Typically, camera operation is restored in about ten
minutes. Although the thermal overload switch will protect the camera, users are advised
to power down and correct the operating conditions that caused the thermal overload to
occur. With some versions of the software, the indicated temperature when the camera is
in thermal overload (thermal switch is in the cut-out state) is -120° C.
Gradual Deterioration of Cooling Capability
With time, there may be a gradual deterioration of the camera’s vacuum. This can affect
temperature performance such that it may be impossible to achieve temperature lock at
the lowest temperatures. In the kind of applications for which cooled CCD cameras are so
well suited, it is highly desirable to maintain the system’s lowest temperature
performance because lower temperatures result in lower thermal noise and better the
signal-to-noise ratio.
Vacuum deterioration occurs primarily as a result of material outgassing in the vacuum
chamber. Because outgassing normally diminishes with time, the rate of vacuum
Caution