Isolation Tests; Figure 4-3 Connections For Same-Channel Isolation Tests - Keithley 2000-Scan Instruction Manual

4-8 Service Information

Isolation tests

These tests check the leakage resistance (isolation) between all HI and LO terminals and from
HI and LO terminals to chassis ground. In general, the test is performed by applying a voltage
(100V) across the terminals and then measuring the leakage current. The isolation resistance is
then calculated as R = V/I. In the following procedure, the Model 617 functions as a voltage
source and as an ammeter. In the V/I function, the Model 617 internally calculates the resistance
from the known voltage and current levels, and displays the resistance value.
Perform the following steps to check isolation:
1.
2.
3.
4.
5.
WARNING
6.
7.
8.
Figure 4-3
Connections for same-
channel isolation tests
Connect a 4" length of Teflon-insulated #22AWG stranded wire to every HI and LO
terminal on the scanner card (both inputs and outputs). Mark the free end of each wire
so you can identify wires when the scanner card is installed.
With the power off, install the scanner card in the multimeter.
Turn on the Model 2001 power.
Turn on the Model 617, and allow the unit to warm up for two hours for rated accuracy.
Select the Model 617 2pA range, and enable zero check and zero correct in that order.
Leave zero correct enabled for the entire procedure.
The following steps use high voltage (100V). Be sure to remove power from
the circuit before making connection changes.
Set the Model 617 voltage source for +100V, and select the 200nA current range. Make
sure the voltage source is still in standby.
Place the Model 617 in the V/I measurement function by pressing SHIFT OHMS.
With the Model 617 in standby, connect the electrometer to OUT A HI and LO terminals
of the scanner card, as shown in
Banana to Banana Cable
Ground Link
Com
Removed
INPUT
V-Source LO
V-Source HI Model 617
Source V and
Measure V/I Unterminated to
Banana Cable
Figure 4-3.
Model 7025
Unterminated
Triax Cable
HI
(Red)
HI
Channel 1
LO
Channel 2-4
HI
Channel 5
LO
4-Pole
HI
Channel 6
LO
Channel 7-9
HI
Channel 10
LO
Model 2000-SCAN
HI
OUT A
LO
HI
OUT B
LO
2-Pole