A-8 620UK Calibration Adjustment Procedure.
All the 620UK Ohmmeter calibration adjustments (trimpots) are located on the DVM PCB (top slot - see
diagram below). The calibration adjustments must take place with the 620UK Ohmmeter Front panel and all
PCBs assemblies must be out of the 620UK chassis.
* Place the 620UK in the 20 Ohm range and short the measurement test leads together.
*
Adjust the unit’s front panel “Zero” knob to a full clockwise position.
* Put the measurement test leads across a known 10.0 Ohm resistance standard. (i.e 0.005% or better)
* Adjust RV401 so the display is the value of the 10 ohm resistance standard.
* Next short the measurement test leads together.
* Place the 620UK Ohmmeter in the 2 Ohm range (front panel range select knob).
* Adjust RV403 (see diagram below) for a reading of .0000 on the display.
* Put the output leads across a known 1.0 Ohm resistance standard (0.005%).
* Adjust RV402 so the ohmmeter displays the same value of the 1.0 Ohm resistance standard.
* Reassemble and verify the other ranges (there are no other adjustments needed)
toward the front panel
DVM PCB (top slot)
toward the back (rear panel)
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