Isolation Tests - Keithley 2000-SCAN-20 Instruction Manual

Isolation tests

These tests check the leakage resistance (isolation) between all HI and LO inputs for each
channel and from the HI and LO inputs to chassis ground. In general, the test is performed by
applying a voltage (60V) across the connections and then measuring the leakage current. The
isolation resistance is then calculated as R = V/I. In the following procedure, the Model 6517A
Electrometer functions as a voltage source and as an ammeter. In the R function, the
electrometer internally calculates the resistance from the known voltage and current levels and
displays the resistance value.
Perform the following steps to check isolation:
NOTE To perform this test, you must custom-wire a cable to connect to the scanner card
connections.
1. Turn off the Model 2000-20 Multimeter if it is on and remove the scanner card.
2. Remove any jumpers or test leads connected to the card.
3. Turn on the Model 6517A Electrometer and allow the unit to warm up for two hours
before testing.
4. Connect a 4 in. length of Teflon-insulated #22AWG stranded wire to every HI and LO
input and output on the scanner card (connectors J1035 and J1036). Mark the free end
of each wire so you can identify the wires when the scanner card is installed.
5. With the power off, install the scanner card in the multimeter.
6. Connect the electrometer to OUT A HI and LO of the scanner card as shown in
Figure
Figure 4-3
Connections for same-channel isolation tests
Banana to
Com
Banana
(Ground Link
Cable
Removed)
Model 6171
Triax Adapter
Model 6517A
Model 7025
Unterminated
Triax Cable
4-3.
Unterminated to
Banana Cable
Source V and
Measure V/I
V-Source LO
V-Source HI
Channel 1
Channel 2-9
Channel 10
HI
(Red)
Channel 11
Channel 12-19
Channel 20
Service Information
HI
LO
HI
LO
4-Pole
HI
LO
HI
LO
Model 2000-SCAN-20
4-7
HI
LO OUT A
HI
OUT B
LO
2-Pole