User`s guide

292
Chapter 7 Tutorial
Measurement Fundamentals
The 4-wire ohms method is used in systems where lead resistances can
become quite large and variable and in automated test applications
where cable lengths can be quite long. The 4-wire ohms method has the
obvious disadvantage of requiring twice as many switches and twice as
many wires as the 2-wire method. The 4-wire ohms method is used
almost exclusively for measuring lower resistance values in any
application, especially for values less than 10 and for high-accuracy
requirements such as RTD temperature transducers.
HI-Sense
V
meter
I
test
LO-Source
HI-Source
R=
V
meter
I
test
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LO-Sense
34970A Refresh UG.book Page 292 Wednesday, February 17, 2010 12:34 PM