Keithley 7172, Instruction Manual

Page: 74 / 98

SECTION 4
Service Information
4-8
NOTE
The following procedure must be performed
at an ambient temperature of 23°C and at a
relative humidity of less than 50%.
1. Turn on the Model 617 and allow it to warm up for
two hours for rated accuracy.
2. With the mainframe power turned off, plug the
Model 7172 into slot 1 of the mainframe. Remove all
other cards from the mainframe, and install the slot
covers.
3. After the prescribed warm up period, select the
Model 617 amps function, and enable zero check.
Select the 2pA range, and zero correct the
instrument.
4. Connect the Model 617 to rows A and B of the
matrix card, as shown in Figure 4-4.
5. Program the Model 617 voltage source for a value of
+100V, but do not yet turn on the voltage source
output.
6. Close crosspoints A1 and B2 by using the switching
matrix front panel controls.
7. With the Model 617 in amps, enable suppress after
the reading has settled.
8. Turn on the Model 617 voltage source output, and
enable the V/I ohms function on the electrometer.
9. After the reading has settled, verify that the resis-
tance is >10T
Ω
(10 13
Ω
).
10. Turn off the voltage source, and enable zero check.
Disable suppress, and select the amps function on
the electrometer.
11. Open crosspoints A1 and B2, and close crosspoints
A3 and B4.
12. Repeat steps 7 through 11 for A3 and B4.
13. Repeat steps 7 through 12 for crosspoint pairs A5
and B6, A7 and B8, A9 and B10, and A11 and B12.
14. Disconnect the electrometer from rows A and B, and
connect it instead to rows C and D.
15. Repeat steps 7 through 13 for rows C and D. The
path isolation for these rows should be >10T
Ω
(10 13
Ω
).
16. Repeat steps 7 through 14 for row pairs E and F, and
G and H. For each row pair, step through the cross-
point pairs 1 and 2, 3 and 4, 5 and 6, 7 and 8, 9 and
10, and 11 and 12. The complete procedure outlined
in steps 7 through 11 should be repeated for each
crosspoint pair. Each resistance measurement for
rows E through H should be >10T
Ω
(10
13
Ω
).
(A) Cut off insulation with knife.
Cut off outer shield.
(B) Strip insulation off inner shield.
(C) Twist inner shield then strip inner conductor.
Twist inner shield and center conductor together,
slip on plastic cover.
(D) Insert wires into hole and wrap around body.
(E) Screw on plastic cover.
1”
Cut
Cut
3/4”
Insulation Over
Inner Shield
Figure 4-5. Triaxial Cable Preparation
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