Keithley 7035, Instruction Manual

Page: 35 / 74

Operation
4-6
Multiplexer switching examples
This paragraph presents some typical applications for the
Model 7035. These include two-wire and four-wire resis-
tance tests.
The Model 7035 can be used to test a large number of resis-
tors using only one test instrument or group of instruments.
Such tests include two-wire and four-wire resistance mea-
surements using a DMM as discussed in the following para-
graphs.
Two-wire resistance tests
Figure 4-5 shows a typical test setup for making two-wire
resistance measurements using one of the nine Model 7035
multiplex banks. The Model 7035 provides the switching
function, while the resistance measurements are made by a
Model 2000 DMM.
Figure 4-5
Two-wire resistance testing
Since only two-pole switching is required for two-wire resis-
tance testing, one Model 7035 card can be used to switch up
to 36 resistors by externally connecting the bank outputs
using customer-supplied jumpers (Figure 4-6). Figure 4-6 is
a simplified schematic, and each input contains two-pole
switching.
Accuracy of measurements can be optimized by minimizing
stray resistance.
Make connecting wires as short as possible to minimize path
resistance. Another technique is to short one of the multi-
plexer inputs, close the shorted channel and then enable the
DMM zero feature to cancel path resistance. Leave zero
enabled for the entire test.
Figure 4-6
1
×
36 multiplex bank
B. Simplified Equivalent Circuit
Ω
R
Model 2000
DMM
7035
DUT
A. Test Configuration
HI
LO
POWER
MODEL 2000 DMM
1
4
4
Single 1
×
4 MUX
DUTs
(4)
7035
1
Single 1
×
36 Multiplexer
DUTs
Instruments
Bank A (1
×
4)
Bank B (1
×
4)
Bank I (1
×
4)
5
1
8 4
Customer-supplied
external bank
connections
1
1
4
4
36
4
32
1