Teledyne Princeton Instruments PI-MAX 3, System Manual

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Chapter 15 Tips and Tricks 189
15.6 Baseline Signal
With the detector completely blocked, the CCD will collect a dark charge pattern,
dependent on the exposure time, detector temperature, and intensifier gain setting.
The longer the exposure time and the warmer the detector the larger and less uniform
this background will appear.
After temperature lock has been established, wait about 5 minutes for the detector
temperature to completely stabilize. Then try taking a few dark charge readings with
the detector operated with the I.I.T. switch set to OFF.
NOTE:
Do not be concerned about either the baseline level of this
background or its shape, unless it is very high, i.e., > 1000
counts (or > 3000 counts at Gain=2 for some cameras).
What you see is not noise. It is a fully subtractable readout
pattern. Each CCD has its own dark charge pattern, unique
to that particular device. In addition, a small offset is built in
to prevent noise or pattern from going below zero. Every
device has been thoroughly tested to ensure its compliance
with Teledyne Princeton Instruments’ demanding
specifications.
15.7 Temperature Lock
If the PI-MAX3 Detector loses temperature lock, 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 too cold temperature. If this happens, an
internal thermo-protection switch will disable the cooler circuits to protect them.
Although the thermo-protection switch will protect the camera, users are advised to
power down and correct the operating conditions that caused the thermal-overload to
occur. Note that the cooling performance of the detector can be enhanced by
circulating water coolant. Refer to
Section 7.5, Temperature Control , on page 68.
Turn the controller off for fifteen or twenty minutes. Then turn it back on and set a
warmer temperature from the software Detector Temperature dialog. Temperature lock
should be re-established within a few minutes.
15.8 Intensifier Alarm
CAUTION!
!
Contact Teledyne Princeton Instruments immediately if
sporadic or continuous unwarranted alarms occur. They
may indicate intensifier damage or another situation that
requires immediate attention.
To reduce the risk of detector damage, PI-MAX3 detectors are equipped with an audible
alarm in the detector head which is activated when the intensity of light falling on the
image intensifier exceeds a preset threshold. While the alarm is sounding, the
photocathode is temporarily disabled. Toggle the I.I.T. switch on the back of the
PI-MAX3 to the OFF position. Cover the detector window and only switch the I.I.T.
switch to ON after the illumination level has been lowered. If the alarm sounds
repetitively even when the illumination level is adequately low, select Safe Mode in the
WinX/32 application or shut the system down and contact the factory for guidance.