Bird Electronic 4314B, Руководство по эксплуатации, Страница: 42 / 48

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Calibrating the Wattmeter
Zero adjustment of the meter is the only calibration required for the
4314B. This should be done any time the meter pointer is not exactly
aligned with the zero mark on the meter scale when no power is being
applied. Zero adjustment must also be performed after the meter or
instrumentation module has been replaced.
1. To assure that the meter reads correctly for both average and peak
operation,
2. Apply direct current from a battery source to the input of the
amplifier circuit (figures 5 and 6, pages 20-21).
The steady direct-current peak level should be the same as the aver-
age current level because no peaks exist in this current.
Apply a direct current and adjust as necessary so that the same read-
ing is attained in both average and peak modes.
Install a voltage-dropping variable voltage dividing potentiometer and
a battery in series with the input of the amplifier.
Make sure the resistor is set for zero output. Connect the positive (+)
side of the circuit to input and the negative (-) side to ground.
Install a voltmeter across the circuit. Slowly operate the potentiome-
ter to adjust output to apply approximately 21 millivolts. Use a suit-
able resistive network.
Check the reading of the meter.
The pointer should deviate or travel about half of full scale. Set the
CW/PEAK switch to PEAK mode while watching the meter pointer.
There should be no deviation of the pointer from average to peak read-
ing.
If the pointer reads a different value for peak reading than for average
reading, adjust potentiometer R8 until the two readings coincide.
Figure 12 Calibration Potentiometer
Calibration
Potentiometer
Access Hole
X