Service Information
5-8
Common-mode isolation tests
These tests check the common-mode isolation (leakage
resistance) between the input (IN) and chassis ground of
every channel.
In general, the test is performed by applying a voltage (42V)
and then measuring the leakage current. The isolation resis-
tance is then calculated as R = V/I. In the following proce-
dure, the Model 6517A functions as a voltage source and an
ammeter. In the R function, the Model 6517A internally cal-
culates the resistance from the known voltage and current
levels and displays the resistance value.
Refer to Figure 5-5 and perform the following steps to test
common-mode isolation.
1. Turn off the Model 7001/7002 if it is on.
2. Connect the Model 6517A to channel 1 as shown in
Figure 5-5. Make sure the voltage source is off. Note
that the voltage source HI is connected to the input (IN).
Electrometer HI can be connected to chassis ground at
the rear panel of the Model 7001/7002.
3. Install the Model 7036 in slot 1 (CARD 1) of the
Model 7001/7002 if it is not already installed.
4. On the Model 6517A, select the ohms function and
choose the 2G
Ω
range.
5. On the Model 6517A, set the voltage source for +42V.
Make sure the voltage source is still off.
6. Place the Model 6517A in the R measurement function.
7. Turn on the Model 7001/7002 and program the main-
frame to close channel 1!1 (slot 1, channel 1).
8. On the Model 6517A, turn on the voltage source.
9. After allowing the reading on the Model 6517A to settle,
verify that it is >1G
Ω
. This measurement checks the
common-mode isolation of channel 1.
10. Turn off the Model 6517A voltage source.
11. Repeat the basic procedure in steps 1 through 10 to
check differential isolation of the other Model 7036
channels. Remember to close the relay of the channel
being checked.
12. Turn off the Model 6517A voltage source and the Model
7001/7002.
Figure 5-5
Common-mode isolation testing
WARNING:
NO INTERNAL OPERATOR SERVICABLE PARTS,SERVICE BY QUALIFIED PERSONNEL ONLY.
WARNING:
NO INTERNAL OPERATOR SERVICABLE PARTS,SERVICE BY QUALIFIED PERSONNEL ONLY.
CAUTION:
FOR CONTINUED PROTECTION AGAINST FIRE HAZARD,REPLACE FUSE WITH SAME TYPE AND RATING.
CAUTION:
FOR CONTINUED PROTECTION AGAINST FIRE HAZARD,REPLACE FUSE WITH SAME TYPE AND RATING.
!
115V
!
90-110V
105-125V
180-220V
210-250V
Banana to
Banana Cable
Model 6517A
Model 7025
Unterminated
Triax Cable
Ground Link
Removed
Unterminated
Banana Cables
Source V and
Measure V/I
HI
HI
(Red)
HI
Each channel:
7036
IN
OUT
Chassis ground
is accessible at
7001/7002
rear panel