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Calibration should only be done by persons familiar with High Voltage testing and safety
procedures.
All calibrations have been done at the factory. Periodic calibration of the output voltmeter and output
currentmeter should be done annually.
NOTE: Refer to Electrical Diagram Section for schematics pertaining to the model number of your test set.
Locating the Calibration Adjustments
The calibration points are shown in the following diagram.
R19
R17
R113
120 kV
20 kV
VOLT
VM
VM
OFFSET
1.
Output Voltmeter
Connect a precision high voltage voltmeter across the output to ground on 20 kV output, with the
Voltage Range switch set to 20 kV. Raise the output to approximately 80% of the output rating. Adjust
the reading on the panel meter (M2) by means of potentiometer R17 to a corresponding reading.
Repeat procedure with precision high voltage voltmeter connected between the 120 kV output and
ground with the Voltage Range switch set to 120 kV. Adjust R19 to match precision voltmeter at 80% of
output rating.
2.
Output Currentmeter
It is necessary to connect adequately rated High Voltage loads (isolated from ground) to the high voltage
unit that will allow each full range current to be drawn at approximately 15% or higher output voltage.
This allows sufficient resolution to adjust current levels.
Place Binding Post Configuration in GUARD MODE. (Jumper clip is installed between "GRD" and
"GND" posts.)
Connect a precision ammeter between the low potential side of the appropriate high voltage load and
the "RTN" post. Select the 20 uA meter range. Raise the output to approximately 80% of the range
rating. Adjust the reading on the panel meter (M1) by means of potentiometer R78 to a corresponding
reading. Repeat for 200 uA, 2 mA and 10 mA ranges adjusting R80, R82 and R84, respectively. (High
Voltage load will need to change when changing range).
An optional method is to use current injection between RTN and GND (Guard Mode).
Do not turn High Voltage on for this method!
DCD 4120-10
SECTION 6: CALIBRATION
CAUTION
R84
R82
R80
10mA
2mA
200µA
CM
CM
CM
:
R78
R77
20µA
CURRENT
CM
OFFSET
6-1
R87
R72
R69
RANGE
110%
10%
OVLD
OVLD
OVLD
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