Princeton 4411-0087 Manuale Utente

Chapter 4 

Temperature Control 

39 

 

Many cameras incorporate a vacuum chamber for enhanced cooling performance. With 
time, there can be a gradual deterioration of the camera’s vacuum. This is turn may 
eventually affect temperature performance to where it may no longer be possible to 
achieve temperature lock at the lowest temperatures. In the kind of low-light imaging 
applications for which cooled CCD cameras are so well suited, it is highly desirable to 
maintain the controller’s temperature performance because the lower the temperature, the 
lower the thermal noise will be and the better the signal-to-noise ratio.  

Vacuum deterioration occurs primarily as a result of outgassing occurring in the vacuum 
chamber. Because outgassing normally diminishes with time, the rate of vacuum 
deterioration in new cameras will be faster than in older ones. As a result, for example, a 
camera that has to be repumped after perhaps a year of operation, may not have to be 
pumped again for several years.  

In any case, should you notice a gradual deterioration in temperature control performance 
indicative of vacuum deterioration, the camera can be repumped. Contact the factory 
Technical Support Dept. for information on refreshing the vacuum. See page 114 for 
contact information. 

The CCD array is subject to damage from condensation if exposed to atmospheric 
moisture when cold. For this reason, the camera should be kept properly evacuated.  

If temperature lock cannot be achieved or maintained, it will be necessary to find and 
correct the problem to be assured of good measurement results. Possible causes could 
include: 

•  The vacuum has deteriorated as described above and needs to be refreshed. 
•  The connectors of the cable that interconnects the controller and the camera need to 

be secured (slide-lock latch or screws as required).   

•  The internal temperature of the camera has gotten 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. Both TE and RTE 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.