Spectral Instruments Series 800, Руководство пользователя

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Spectral Instruments
Pt # 2500- 57
signal in electrons per pixel per second. That value should agree with the test
report to within 10%. If the dark signal is too high something is wrong.
The usual cause of reported high dark turns out to be a light leak in the
application. It does not take very much like leaking into the application to
mimic high dark current. If possible, blank off the CCD front and see if the
symptom disappears. Otherwise be as careful as possible to shut off all room
lights and application illuminators and repeat the dark measurement. If it
decreases at all, there was a light leak and the problem is still possibly light
leaking into the camera.
If there is absolutely no light leak, then how much too high a dark current
reading is an indicator. If it is just a little too high, check the pressure reading
inside the camera head. If it is above 2 torr it is possible that the CCD is
being warmed by conduction. In any event, if the camera pressure is above 2
torr it is time to pump the camera.
If the dark is very much too high it is possible that the CCD has become
separated from the cold block where the temperature is measured. To
determine if this is the case (and incidentally to also fix the problem if it is)
allow the camera to warm up to room temperature and then cool it back down.
If the problem persists and the pressure is below 2 torr and the temperature
indicated for the CCD is OK, then it is possible that the cooling capability of
the TE cooler is at margin.
8.4 Camera Does Not Cool
Several possibilities exist. One is that the TE power supply has failed, the
other is that the camera vacuum is not high enough. Generally, the back plate
of the camera is slightly warm unless a refrigeration unit is in use. If one is,
turn it off for a bit and see if the back plate becomes warm to the touch. If the
back plate is/becomes warm, the TE power supply is operating. If the back
plate is quite warm the water circulation is probably not operating properly. If
the camera pressure is high and the dark is high the camera needs to be
pumped.
8.5 Condensation On The Camera Window
The most likely scenario is that the vacuum needs to be refreshed.