Table of Contents
Advertisement
Service Information
4.6.3 Offset current verification
Recommended equipment
• Model 707A Switching Matrix
• Model 617 Electrometer
• Model 7078-TRX-3 Triax Cable
• Model 6172 2-slot male to 3-lug female triaxial adapter
Test connections
Figure 4-3 shows the test connections for offset current
verification. The Model 7174A row being tested is to be
connected to the Model 617 Electrometer input through the
triaxial cable and the triaxial adapter. Note that the
electrometer ground strap is to be removed, and the
electrometer should be operated in the unguarded mode.
Procedure
NOTE
The following procedure should be per-
formed at an ambient temperature of 23°C
and at a relative humidity of less than
60%.
1. Turn on the Model 617 power and allow it to warm up
for two hours before beginning the verification
procedure
3-Lug Triax Adapter
617
A
Equivalent Circuit
Figure 4-3
Offset verification test connections
4-6
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
6172 2-Slot to
Guard off
617 Electrometer
7174A
2. With the power off, install the Model 7174A in the
desired slot of the Model 707A Switching Matrix.
Remove all other cards from the instrument, and install
the slot covers.
3. After the prescribed warm up period, select the amps
function and the 2pA range on the Model 617. Zero cor-
rect the instrument, and then select autoranging.
4. Connect the Model 617 to row A of the Model 7174A,
as shown in Figure 4-4.
5. Close crosspoint A1 by using the Model 707A front
panel controls.
6. Disable zero check on the Model 617, and allow the
reading to settle.
7. Verify that the offset current reading is <500fA.
8. Enable zero check on the Model 617, and open cross-
point A1.
9. Repeat steps 5 through 8 for crosspoints A2 through
A12. Only one crosspoint at a time should be closed.
10. Disconnect the triax cable from row A, and connect it
instead to row B.
11. Repeat steps 5 through 8 for crosspoints B1 through
B12. Only one crosspoint at a time should be closed.
12. Connect the triax cable to each succeeding row and
repeat steps 5 through 8 for each of the row's
crosspoints.
Connect Cable
to Row Under
Test
7078-TRX-3 Triax Cable
Ground Link
Removed
7174A
7174A
KEITHLEY
8 x 12 LOW
CURRENT MATRIX
SIGNAL
COLUMNS
200V PK
200V PK
GUARD
200V PK
ROWS
1
A
2
B
3
C
4
D
5
6
7
8
E
9
F
10
G
11
H
12
WARNING:
!
TIGHTEN MOUNTING SCREWS
TO ENSURE PROPER
CHASSIS GROUND
Matrix Card
Advertisement
Table of Contents
