NAME PLATE, TR 1C3935 - Caterpillar

(B) Accuracy Check Procedure
This procedure should be performed at least once a year to ensure the ammeter is within specifications. The following checks must be made with all components stabilized at a room temperature of 25°C 5°C (77°F 9°F).
The following instructions must be followed exactly or the results will not be correct. Also, the 6V6124 Calibration Coil must be used to get accurate results with this Ammeter.
(1) Connect the 21 Volt power supply (1), or a 12 Volt battery, to 12 Volt DC terminals (2) on the calibrator with 18 gauge or larger wire. Connect the (+) positive supply lead to (+) positive and the (-) negative supply lead to (-) negative.(2) Connect digital multimeter (3) to VOLTMETER terminals (4) using the meter test leads. Set the meter to the 20 VDC range.(3) Connect 6V6124 Calibration Coil (5) leads into coil jacks (6); red plug in the (+) positive and black plug in the (-) negative.(4) If a power supply is used instead of a battery, turn it on and set the output voltage at 18 Volts (12 Volts can be used if 18 Volts is not available, but maximum calibration current will be lower). NEVER USE MORE THAN 21 VOLTS OR DAMAGE TO THE AMMETER WILL BE THE RESULT. If a battery is being used, make sure it is fully charged. Open the jaws of the ammeter and inspect the core closure points to be sure they are clean and free of all foreign material. If necessary, clean the points. Close the jaws slowly to avoid snapping them.(5) Depress the power trigger on the ammeter and lock the trigger in the ON position. Let the ammeter warm up for several minutes. If the low battery indicator appears during the test, replace the batteries.(6) Put AC-DC Mode Switch (7) in the DC position. Open the jaws of the ammeter and place the 6V6124 Coil in the aperture of the ammeter. Make sure the arrow on the coil points in the same direction as the arrow on the ammeter. Close the jaws slowly. Move the coil slightly to be sure it is loose in the aperture and the jaws are tightly closed.(7) Put the ammeter in the position shown so 6V6124 Calibration Coil is on current selector switch knob (9). Keep the ammeter and the coil in this position during the entire test procedure. The 6V6124 Calibration Coil is accurate when used in one position only. It must be held straight out from the end of the ammeter as shown. Any change from this position will cause an error in the readings. To help keep the coil in this position during test, put the coil on the CURRENT SELECTOR switch knob with the Ammeter in the location as shown.(8) Adjust DC ZERO control (8) until the digital display reads 000.(9) Turn CURRENT SELECTOR knob (9) to the number one position for the lowest current setting. Press PUSH TO CALIBRATE button (10) and make a comparison between the