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TESTING, CALIBRATION, AND TROUBLESHOOTING
TESTING OF LCD
With no test leads connected to the meter, move the selector switch around the dial. You should obtain the following
readings. A (–) sign may also be present or blinking.
1) ACV Range:
750
200
2) DCA,10A Ranges:
200μ
2m
20m
200m
10A
If any of these tests fail:
a) Check that the battery is good.
b) Check the values of resistors R1 - R7, R30, VR1.
c) Check the values of capacitors C1 - C5, C7.
d) Check the PC board for solder bridges and bad solder connections.
e) Check that the slide contactors are seated correctly.
f ) Check that the LCD and zebras are seated correctly.
CALIBRATION
Refer to the METER OPERATION section for test lead connections and measurement procedure.
A/D CONVERTER CALIBRATION
Turn the range selector switch to the 20V position and connect the test leads to the VΩmA and COM sockets. Using another
meter of known accuracy, measure a DC voltage of less than 20 volts (such as a 9V battery). Calibrate the kit meter by
measuring the same voltage and adjusting VR1 until the kit meter reads the same as the accurate meter (do not use the
kit meter to measure its own battery). When the two meters agree, the kit meter is calibrated. Turn the knob to the OFF
position and remove the voltage source.
SHUNT WIRE CALIBRATION
To calibrate the shunt wire, you will need a 1A current source such as a 5V
power supply and a 5Ω, 5W resistor. If no supply is available, it is not
important to do this test. Set the range switch to the 10A position and connect
the test leads as shown in Figure L. If the meter reads higher than 1A,
resolder the shunt wire so that there is less wire between the 10A DC and
COM sockets.
If the meter reads low, resolder the shunt wire so that there is more wire
between the sockets.
If the calibration fails:
a) Check the PC board for solder bridges and bad solder connections.
b) Check the value of resistors R3, R8 - R10, and capacitor C4.
HV 0 0 0
3) Ohms, Diode and h
0 0.0
0 0.0
.0 0 0
0.0 0
0 0.0
0.0 0
4) DCV Range:
-8-
Ranges: B indicates blank.
FE
h
FE
Diode (
)
200
2k
20k
200k
2M
200m
2
20
200
1000
Power Supply
123
+
5VDC
5Ω
5 Watts
10A DC
VΩmA
COM
0 0 0
1 B B B
1 B B.B
1.B B B
1 B.B B
1 B B.B
1.B B B
0 0.0
.0 0 0
0.0 0
0 0.0
HV 0 0 0
–
Figure L
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