TI47UH1 MPU-24
19
4
Operating Procedures
Check Unit Internal Resistance (Test for Shorts)
It is essential to test for shorts to detect any problems with the unit. First, set the multimeter to the “resistance”.
Next, test to see if both terminals are isolated from the chassis ground and the line ground using the steps
below. In steps 2, 3, 5 and 6, a reading of greater than 10 MΩ will assure no shorts exist. In steps 1 and 4,
the multimeter should read less then 1 Ω.
Check DC Voltage Reading at DC Receptacle Terminals
To verify that the power cells are fully charged, set the digital
multimeter to measure dc voltage. Place the positive probe (red)
on the positive post of the DC Output Connector, as shown in Figure
4.9.3. Next, place the negative probe on the negative post. The
multimeter display should read approximately 28.5 Vdc (± 0.5 Vdc)
when power cells are fully charged and the unit is plugged into an
ac power source. When the unit is not plugged into an ac power
source, the multimeter display should read 25.5 Vdc.
Figure 4.9.3 – Testing DC Receptacle
1.
Place the negative probe on the ac
ground probe ( J or L) and the posi-
tive probe on an exposed part of the
metal case.
2.
Move the positive probe to the dc
positive post on the DC Output Con-
nector.
3.
Move the positive probe to the dc
negative post on the DC Output Con-
nector.
4.
Move the positive probe to one of the
four screws securing the DC Output
Connector to the unit casing.
5.
Move the negative probe to the dc
negative post on the DC Output Con-
nector.
6.
Move the negative probe to the dc
positive post on the DC Output Con-
nector.