Pyrocam IV Operator’s Manual Document No. 50337-001 Rev F 2/21/2017 Page 23
3.5.1 Calibrate Cycle
The Calibrate operation is performed in the Pyrocam when a Calibrate command (see
APPENDIX F) is sent to the Pyrocam firmware. This process establishes a zero set-point
within the Pyrocam that corrects for circuit and ADC offset errors. It also sign adjusts for
the pyro-electric crystal’s polarity and dynamic range.
A Calibrate cycle is initiated in the Pyrocam each time an Ultracal cycle is initiated in
BeamGage.
3.5.2 Ultracal Cycle
An Ultracal cycle begins after the above Calibrate cycle is completed. The Ultracal
operation is performed completely in BeamGage. Ultracal will average 64 dark frames to
establish a new baseline that is accurate to fractional count precision. This extra precision
allows beam width and centroid calculations to be as precise as possible.
Ultracal operations should be performed whenever any of the following conditions are
changed:
1. A change of the Pulsed/Chopped mode selector
2. A change in pulse trigger repetition rate
3. A change of Chopper frequency
4. A change of Exposure time
5. A change of the Gain setting
6. A change in background radiation (including room temperature or changes caused
by varying the optical path)
7. A change in the Pyrocam operating temperature
3.5.3 Performing an Ultracal
After setting up the Pyrocam, in either Pulsed or Chopped mode, an Ultracal cycle
can be performed. It is recommended to wait approximately 30 minutes after powering
up the Pyrocam so that it reaches thermal equilibrium. If a warm up period is not
possible, the Ultracal cycle should be rerun every 5 minutes or so during the warm-up
phase.
To execute an Ultracal cycle, do the following:
STEP 1. In Pulsed mode, provide stable periodic trigger pulses to the Pyrocam at
the rate for which operation is required. Note: if you are operating below
3Hz in single shot mode, an external trigger is not required during the
Ultracal cycle. Adjust the Exposure, Delay, and Gain values as needed.
In Chopped mode, external trigger pulses are not required. Adjust the
Chop Rate and Gain values as needed.
STEP 2. Block the laser beam, from the Pyrocam’s detector. If you are using a lens,
cover it with an opaque material or close its iris. If the imager’s window can
transmit visible light. or if no window is installed, all operations should be
performed under subdued room lighting conditions.
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