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5.3.9 Common-mode isolation tests
These tests check the common-mode isolation (leakage
resistance) between high (H) and low (L) of every
channel.
In general, the test is performed by applying a voltage
(100V) 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 volt-
age 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.
Refer to Figure 5-6 and perform the following steps to
test common-mode isolation.
1. Turn the Model 7001 off if it is on.
2. Connect the Model 617 to Channel 1 as shown in
Figure 5-6. Make sure the voltage source is in
standby. Note that the voltage source HI is con-
nected to both input (IN) high (H) and low (L) by
installing a jumper. Electrometer HI can be con-
nected to chassis ground at the rear panel of the
Model 7001.
3. Install the Model 7013 in slot 1 (CARD 1) of the
Model 7001 if it is not already installed.
Banana to Banana Cable
Ground Link
Removed
Source V and
Measure V/I
Figure 5-6
Common-mode isolation testing
INPUT
Model 617
Unterminated
Banana Cable
Chassis ground is
accessible at 7001
rear panel
The following steps use high voltage
(100V). Be sure to remove power
from the circuit before making con-
nection changes.
4. 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.
5. On the Model 617, set the voltage source for +100V,
and select the 20nA current range. Make sure the
voltage source is still in standby.
6. Place the Model 617 in the V/I measurement func-
tion by pressing SHIFT OHMS.
7. Turn on the Model 7001 and program the Model
7001 to close Channel 1!1 (Slot 1, Channel 1).
8. On the Model 617, disable zero check and press
OPERATE to source +100V.
9. After allowing the reading on the Model 617 to set-
tle, verify that it is >10G Ω . This measurement
checks the common-mode isolation of Channel 1.
10. Enable zero check on the Model 617 and place its
voltage source in standby.
11. Repeat the basic procedure in steps 1 through 10 to
check differential isolation of the other channels of
the Model 7013. Remember to close the relay of the
channel being checked.
12. Place the Model 617 in standby and turn the Model
7001 off.
Model 7025
Unterminated
Triax Cable
Each channel :
HI
(Red)
H
HI
IN
L
L
Jumper
OUT
H
Service Information
WARNING
7013
5-11
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