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F-20 TROUBLESHOOTING & REPAIRF-20
METER CALIBRATION ADJUSTMENTS (continued)
FIGURE F.1 – TRIMMER
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Note: The Precision TIG meter circuits are factory calibrated for the accuracy of the ammeter and voltmeter and should not need adjustment. However, the factory trimmers are accessible inside the control box:
CALIBRATION CHECK
The Digital Meter Calibration Trimmer is located on the back of the meter housing near the right side connec- tor plug (with two leads and a jumper attached). This trimmer adjusts calibration of the meter used for both ammeter and voltmeter readings, so its calibration should be checked first, as follows:
1.Set the TIG mode and, without closing the arc start switch, preset the panel maximum output control so the panel digital meter reads 200 amps.
2.Using a DC (avg.) digital test voltmeter with at least 0.5% accuracy at 1,000v, measure the DC voltage between (+) pin 2 (lead #303) and
3.This voltage should match the 200A panel meter reading (as 0.200v, or 200mv) within 1%. If not, adjust the trimmer so that the panel meter accuracy is corrected. (See Figure F.1)
