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802BT/802R Video Test Generator User Guide 47
Calibrating the generator
The 802BT/R generator can calibrate itself. Once calibrated, the generator does not
require periodic calibration. There are no physical controls to adjust. All calibration is
electronic. Calibration factors are saved in non-volatile memory.
The calibration accuracy of the generator for analog video voltage swing is specified to be
±14mV (or ±2% for a nominal 700mV signal). Using a typical oscilloscope such as a
Tektronix VM700T, which might have a swing measurement accuracy of ±14mV, we
should expect readings between 674mV to 726mV.
You can also set the analog output calibration factors to values other than those set by the
generator's own self-calibration function. Each channel is calibrated using two
independent zero calibration points, and two independent slope calibration points.
Interpolation equations for the different video types are used to set the caldac values that
controls the output sync and voltage levels to the correct values.
Follow the procedures below to calibrate the generator.
To self-calibrate the generator using the front panel:
1. It is not necessary to load the outputs of a generator during self-calibration. However,
attaching a nominal load may yield a slight increase in accuracy.
2. Simultaneously depress all three R, G and B video gate keys and power cycle the
generator.
The LCD will display a special message indicating that it is about to do a
self-calibration.
3. Release the R, G and B video gate keys and the generator will begin its self-calibration
routine.
You will see calibration factors flash on the display. Observe the display for any error
messages that might occur. If an error message appears, make a note of it and call your
technical support representative for further assistance.
To self-calibrate the generator using the command interface:
1. Establish a terminal session with the generator. See “Setting up a terminal connection
with the generator” on page 14.
2. Enter the following command:
SCAL
The generator then goes through a complete calibration procedure.
To view analog calibration factors:
1. Enter the following commands to view the analog video Red, Green, Blue calibration
factors: