Differential And Common-Mode Isolation Tests - Keithley 7011-S Instruction Manual

Service Information
5.3.8 Differential and common-mode isola-
tion tests
These tests check the leakage resistance (isolation) be-
tween HI 0 and LO Q (differ&ial), and from HI @I)
and LO CL) to chassis kommon-mode) of every bank
and channeL In general, the test is performed by apply-
ing a voltage NJOv) ~CXISS the terminals and then mea-
suring 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 am-
meter. In the V/I function, the Model 617 intemalIy cal-
culates the resistance from the known voltage and
current levels, and displays the resistance value.
+rform the following steps to check differential and
::ommon mode isolation:
1. Turn the Model 7001 off if it is on, and remove any
jumpers and test leads connected to the multiplex-
er 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.
WARNING
The following steps use high voltage
(100X9. Be sure to remove
power
from the circuit before making con-
nection changes.
4.
On the Model 617, set the voltage source for +lOOV,
and select the 2CGnA current range. Make sure the
voltage source is still in standby.
5.
Place the Model 617 in the V/I measurement func-
tim by pressing SHFI OHMS.
6. With the Model 617 in standby, connect the elec-
trometer to Bank A of the multiplexer card, as
shown in Figure 5-6.
7.
install the Model 7011 in slot 1 CARD 1) of the
mainframe, and turn the Model 7001 on.
8. Make sure all the relays are open. (press OPEN
ALL on the Model 7001.)
9.
On the Model 617, disable zero check, and press
olmL4TF. to source 1ooV.
10. After allowing the reading on the Model 617 to set-
tle,verify that it is >lGQ (1O'Q). This measurement
is the differential leakage resistance (isolation) of
BankA.
11. Place the Model 617 in standby and enable zero
check
Figure 5-6
Differential isolation test connections
3-12