Heathkit Model IM-103

Line Voltage Monitor

Calibration Procedure

· With the meter off, the meter pointer should be over the 90 volt indication on the meter face.  If it is not, turn the mechanical zero-adjust screw at the bottom of the meter until the pointer is properly aligned

Ancillary Equipment Needed

AC VTVM (optional)

Variable AC voltage Source (optional)

* * * * * * *

INITIAL ADJUSTMENTS

(    )         Set the HI and LOW controls at the center of their rotation.

(    )         Set the NORM-CAL switch in the CAL position.

ADJUSTMENT WITHOUT INSTRUMENTS

(    )         Connect the instrument to the AC line.

(    )         Adjust the LOW control to indicate 137.5 VAC.

(    )         Set the NORM-CAL switch to NORN.

· To complete the following steps it is necessary to know the correct AC line voltage.  If you do not know the correct power line voltage, do not perform this step.

(    )         Adjust the HI control to indicate the voltage of the AC line being measured.

(    )         Calibration procedure is complete.

ADJUSTMENT WITH INSTRUMENTS

· A variable AC voltage source and an accurately calibrated AC voltmeter are required for the following steps.

(    )*       Adjust the LOW control for a meter reading of 95 VAC.

(    )*       Set the output from the variable supply to 125 VAC.

(    )*       Adjust the HI control for a meter reading of 135 VAC.

(    )         Repeat the above three marked steps* until the voltage monitor reads the same as the AC VTVM at 95 VAC and 135 VAC.

(    )         Calibration procedure is complete.