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Operation
2
1
DUTs
(10)
2
10
2
1
DUTs
(10)
2
10
2
1
DUTs
(10)
2
10
2
1
DUTs
(10)
2
10
Multiplexer
Note : The 7015 Bank-to-Bank
jumpers must be removed.
Figure 4-8
Connecting multiplexer and matrix cards together
4.5
Measurement considerations
Many measurements made with the Model 7015 are subject
to various effects that can seriously affect low-level measure-
ment accuracy. The following paragraphs discuss these ef-
fects and ways to minimize them.
4.5.1 Thermoelectric potentials
Thermoelectric potentials (thermal EMFs) are small electric
potentials generated by differences in temperature at circuit
connecting points such as multiplexer card terminals and
connectors. Thermal EMFs can also be generated by the sol-
id-state relays themselves.
4-12
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Backplane
Jumpers
2
2
A
2
B
C
2
D
7001/7002
Backplane
7015
Card
Instruments
1
2
Rows
3
4
7012 Matrix Card
Thermoelectric generation
Figure 4-9 shows a representation of how thermal EMFs are
generated. The test leads are made of the A material, while
the source under test is the B material. The temperatures be-
tween the junctions are T1 and T2.
In the unlikely event that the two junction temperatures are
identical, the thermal EMFs will exactly cancel because the
generated potentials oppose one another. More often, the two
junction temperatures will differ, and considerable thermal
EMFs will be generated.
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