Pyrocam IV Oper
ator’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.
