Model 2790 SourceMeter
®
Switch System User’s Manual
6-9
shows the simplified test circuit for using the
Ω
2 function of the Model 2790 with
the 7751/7752/7753 module to measure high ohms DUT (i.e., insulation resistance) up to
120M
Ω
. The DUT is connected to channels 10 and 11 (Bank 4) of the 7751/7752/7753. To
connect the DUT to the DMM of the Model 2790, channels 10, 11, 13, and 18 must be
closed. Note that the voltage across the DUT
is
sensed through the fuse resistance, so that
measurement accuracy can be affected by fuses when making low ohms measurements.
NOTE
When using the 2-wire ohms function of the Model 2790 to measure a resistance
through one of the 775X modules, there will be an offset in the measured value
due the signal path resistance of the 775X module (see
). This path resistance is due to safety circuitry (fuses) in
the module. The offset can be corrected for by measuring a zero ohm load (short
circuit) and then using the REL function (see Section 5 of the Model 2790 Refer-
ence Manual) to remove the offset. 4-wire ohms measurements are not affected
by the safety circuitry.
Figure 6-6
Using Model 2790 2-wire ohms with 7751/7752/7753 module
(high ohms measurements)
DMM
Ω
2
Input HI
Input LO
DUT
18
Ch 10
Ch 11
= Channel closed by user (multiple channel operation).
Keithley 2790
18
10
11
13
13
HI
Source
<120M
Ω
Source
LO
Keithley 7751/7752/7753
Fuse
Resistance