Keithley 7015-C, Инструкция по эксплуатации

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Service Information
5-4
5.3.5 Offset current tests
These tests check leakage current between HI (H) and LO
(L) (differential offset current) and from HI (H) and LO (L)
to chassis (common-mode offset current) of each pathway. In
general, these tests are performed by simply measuring the
leakage current with an electrometer. In the following proce-
dure, the Model 617 is used to measure the leakage current.
Test connections are shown in Figure 5-2.
Perform the following procedure to check offset current:
1. Turn off the Model 7001/7002 if it is on, and remove any
jumpers or wires connected to the multiplexer card.
2. Connect the triax cable to the Model 617, but do not
connect it to the multiplexer card at this time.
3. Turn on the Model 617, and allow the unit to warm up
for two hours before testing. After warm-up, select the
200pA range, and enable zero check and zero correct in
that order. Leave zero correct enabled for the entire pro-
cedure. Also, be certain that V-
Ω
, GUARD is OFF and
that the ground strap is connected to LO.
4. Connect the triax cable to Bank A HI and LO, as shown
in Figure 5-2A.
5. Install the Model 7015 in slot 1 (CARD 1) of the Model
7001/7002.
Figure 5-1
Path resistance test connections
NEXT
DISPLAY
PREV
POWER
DCV ACV DCI ACI
Ω
2
Ω
4 FREQ TEMP
REL TRIG STORE RECALL
INFO LOCAL CHAN SCAN CONFIG MENU EXIT ENTER
RANGE
AUTO
FILTER MATH
RANGE
SENSE
Ω 4 WIRE
HI
INPUT
LO
INPUTS
CAL
500V
PEAK
F
R
FRONT/REAR
2A 250V
AMPS
350V
PEAK 1100V
PEAK
2001 MULTIMETER
Model 2001 Multimeter
(Measure 4-Wire Ohms)
A
B
C
D
1 3 4 5 6 7 8 9 10 2
H
L
H
L
H
L
H
L
H L H L H L H L H L H L H L H L H L H L
Note : Connections are set
up to test Bank A HI
Jumpers
Bank
Outputs
Bank Inputs
Model 7015
Sense
Ω
HI
Input HI
Input LO
Sense
Ω
LO
6. Turn on the Model 7001/7002, and program the unit to
close Channel 1!1 (Bank A, Input 1).
7. On the Model 617, disable zero check, and allow the
reading to settle. Verify that the reading is <1nA. This
specification is the offset (leakage) current of the path-
way.
8. Enable zero check on the Model 617 and open Channel
1!1 from the front panel of the Model 7001/7002.
9. Repeat the basic procedure in steps 6 through 8 to check
the rest of the pathways (Inputs 2 through 10) of Bank A
(Channels 1!2 through 1!10).
10. Turn off the Model 7001/7002, and change the elec-
trometer connections to Bank B.
11. Repeat the basic procedure in steps 6 through 10 to
check Bank B, Inputs 1 through 10 (Channels 1!11
through 1!20).
12. Repeat the basic procedure in steps 6 through 11 for
Banks C and D (Channels 1!21 through 1!40).
13. Turn off the Model 7001/7002 and change the electrom-
eter connections, as shown in Figure 5-2B. Note that
electrometer HI is connected to HI and LO of the Bank
A output, which are jumpered together. Electrometer
LO is connected to chassis.
14. Repeat steps 6 through 12 to check that the common
mode offset current is <1nA.
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