Manual

7
SECTION - 5
CALIBRATION
DIGITAL PANEL METER (DPM) :
The reference voltage of the DPM is set to 1.00V.
The Main pcb(767/01) has two test points marked DPM
and GND. With reference to this test point (GND),
measure the voltage on pin 36 of the IC1(7107) on DPM
pcb (DPM-0295). Set this voltage to 1.00V by adjusting
the preset PR1 on the DPM pcb.
MAIN PCB :
The Main pcb has two test points marked DPM and GND.
All calibration should be done with reference to the test
point marked GND.
With the Digital Wattmeter switched off, disconnect the
VIN H and VIN L inputs of the Main pcb. (Take care to
maintain the correct connection sequence during
reconnection later). Switch on the Digital Wattmeter.
DC OFFSET ADJUSTMENTS :
Adjust the presets as shown in the table and ensure that
the DC voltage at the corresponding test point is within 0
V ± 1 mV.
Adjust preset Test Point
PR14 (VOFF1) TPV1
PR11 (VOFF2) TPV2
PR6 (IOFF1) TPI1
PR7 (IOFF2) TPI2
PR12 (WOFF1) TPW1
PR13 (WOFF2) TPW2
6
COMMON MODE REJECTION
(CURRENT MEASUREMENT) :
Monitor the waveform on TPI1 on an oscilloscope and
adjust preset PR5 (I-CMRR) so that the trace is flat. This
can also be verified on an AC millivoltmeter. The reading
will be minimum at the correct setting. With the Digital
Wattmeter switched off, reconnect the VIN H and VIN L
inputs on the Main pcb. Switch on the Digital Wattmeter.
VOLTAGE CALIBRATION :
Measure the line voltage with a multimeter (AC voltage
measurement). Adjust preset PR10 (VCAL) so that the
Digital Wattmeter shows the correct line voltage.
CURRENT CALIBRATION :
Connect a suitable resistive load across the output
terminals and an AC current meter in series with it.
Select the current function "A". Adjust preset PR9 (ICAL)
so that the Digital Wattmeter shows the correct load
current.
POWER (W) CALIBRATION :
Connect a suitable resistive load across the output
terminals. Measure the voltage and current as given above.
Select the power function "W". Adjust preset PR15
(WCAL) so that the Digital Wattmeter shows the correct
power as given by the following equation :
W = V * I
(Since the load is resistive, power factor is 1)