SECTION 8 CALIBRATION
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SECTION 8
CALIBRATION
8 CALIBRATION
This section describes calibration of a UPC. To fully calibrate the SYSTEM for output voltage and
metering accuracy, it is necessary to perform a complete EXTERNALLY REFERENCED CALIBRATION.
The Exterally Referenced Calibration requires NO manual adjustment or access of internal circuits.
Externally Referenced Calibration achieves high calibration accuracy of the oscillator and metering
circuits. This procedure must be performed in order for the CSC (Continuous Self Calibration) function
to operate accurately as accurate metering assures that the CSC function will be able to track the
programmed value.
8.1 CALIBRATION INTERVAL
Accurate control and measurement requires calibration every six months or after any service.
8.1.1 TEST EQUIPMENT REQUIREMENTS
The test equipment listed below is required for calibration of the UPC installed in a Power Source.
1. Digital Voltmeter: 4½ Digit True-RMS responding, 1200 Hz. bandwidth, min.
2. Frequency counter: 5 digit counter, min.
3. Oscilloscope: (Optional)
4. High current load (capable of 60% Peak rated output current of power source)
5. Ammeter probe (Shunt type preferred) or ammeter capable of reading RMS amps.
8.2 EXTERNALLY REFERENCED CALIBRATION
The UPC is designed to be easily calibrated in the field. Calibration may be required in order to ensure that the
EXECUTEd voltage produced by the power source is the same as the COMMAND voltage, that the CSC function
is able to precisely match the output voltage of the power source to the programmed command voltage, and that
the metered values correctly represent the actual output. Potential sources of error which may cause difference
between these are:
a) Drift in oscillator signal level.
b) Power Amplifier gain drift.
c) Output transformer turns ratio error. i.e. Actual turns ratio different from encoded turns ratio.
d) Difference between INT SENSE metering circuit and EXT SENSE metering circuit.
e) Internal metering inaccuracy.
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