The 4-wire ohms method is used in systems where lead resistances c an
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 10Ω and for high-accuracy
requirements such as RTD temperature transducers.
I test
Vmeter
HI-Source
LO-Source
LO-Sense
HI-Sense
R = Vmeter
Itest
Chapter 8 Tutorial
Measurement Fundamentals
370