Keithley 7999-2, Instruction Manual

Page: 34 / 44

Service Information 4-7
Common-mode isolation tests
CAUTION The following procedure uses the Model 6517A voltage source to measure
resistance. To avoid damage to the Model 7999-2, use the Model 6517A
manual ohms mode to limit the test voltage to 30V as outlined in the
procedure.
Perform the following steps to check common-mode isolation:
1. Turn on the Model 6517A Electrometer, and allow the unit to warm up for one hour
before testing.
2. Select the Model 6517A ohms function and 2G
Ω
range, and enable zero check. Make
sure the voltage source is in standby.
3. Connect the electrometer to the Model 7999-2 channel being tested, as shown in Figure
4-4. Note that electrometer INPUT HI is connected to the tested channel, while VOLT-
AGE SOURCE HI is connected to system ground.
4. Put the Model 6517A in the manual ohms mode, and set the voltage source to +30V.
5. Place the Model 6517A voltage source in operate, and disable zero check.
6. Allow the reading to settle, then verify that the resistance reading is >1G
Ω
.
7. Enable zero check, and place the Model 6517A voltage source in standby.
8. Repeat steps 3 through 7 for all other channels on the card.
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.
INPUT
250V PEAK
!
LINE RATING
50-60HZ
50VA MAX
AC ONLY
LINE FUSE
SLOWBLOW
1/2A 90-125V
1/4A 180-250V
IEEE-488
(CHANGE IEEE ADDRESS
WITH FRONT PANEL MENU)
DIGITAL
I/O
TRIG LINK
1
15V
LO
HI
RS232
!
MADE
IN
U.S.A.
PREAMP OUT
250 PEAK
COMMON 2V ANALOG
OUTPUT
TEMP
TYPE K
HUMIDITY
OPTION SLOT
V SOURCE
EXT TRIG
IN
MTR COMP
OUT
INTERLOCK
SELECTED
LINE VOLTAGE
90-110V
105-125V
180-220V
210-250V
1010V
PEAK
750V
PEAK
Model 6517A Electrometer
Model 7999-2 Relay
Under Test. See Section 2
for Detailed Connections.
Connect Voltage
Source HI to
System Ground
In
Out
H
L
G
Close
Relay
INPUT
Voltage Source HI
Connect INPUT HI
to Relay
Figure 4-4
Common-mode
isolation connections