Differential And Common-Mode Isolation Tests - Keithley 7015-S Instruction Manual

5.3.8 Differential and common-mode isolation
tests
These tests check the leakage resistance (isolation) between
HI (H) and LO (L) (differential), and from HI (H) and LO (L)
to chassis (common-mode) of every bank and channel. 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 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 differential and com-
mon mode isolation:
1. Turn off the Model 7001/7002 if it is on, and remove any
jumpers and test leads connected to the multiplexer
card.
2. Turn on the Model 617, and allow the unit to warm up
for two hours for rated accuracy.
3. On the Model 617, select the 2pA range, and enable zero
check and zero correct in that order. Leave zero correct
enabled for the entire procedure.
Banana to Banana Cable
Ground Link
Removed
INPUT
Model 617
Unterminated
Banana Cable
Note : Setup shown is configured to
test isolation between HI and
LO of Bank A.
Figure 5-6
Differential isolation test connections
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4. On the Model 617, set the voltage source for +100V, and
5. Place the Model 617 in the V/I measurement function by
6. With the Model 617 in standby, connect the electrometer
7. Install the Model 7015 in slot 1 (CARD 1) of the main-
8. Make sure all the relays are open. (Press OPEN ALL on
9. On the Model 617, disable zero check, and press OPER-
10. After allowing the reading on the Model 617 to settle,
11. Place the Model 617 in standby, and enable zero check.
Model 7025
Unterminated
Triax Cable
1 2 3
A
HI
(Red)
B
C
D
H L H L H L H
WARNING
The following steps use high voltage
(100V). Be sure to remove power from
the circuit before making connection
changes.
select the 200nA current range. Make sure the voltage
source is still in standby.
pressing SHIFT OHMS.
to Bank A of the multiplexer card, as shown in Figure 5-
6.
frame, and turn on the Model 7001/7002.
the Model 7001/7002.)
ATE to source 100V.
verify that it is >1G Ω (10 Ω ). This measurement is the
9
differential leakage resistance (isolation) of Bank A.
Bank Inputs
4 5 6 7 8
L H L H L H L H L H L
Model 7015
Service Information
9 10
H
L
H
L
Bank
H
Outputs
L
H
L
H L
5-11