RESISTOMAT
®
Model 2302-V001
Page 8
Introduction &
applications
Description of functions
Brief guide
Operation
Calibration
Test and offset
instructions
RS232 data
output
Accessories and Circuit diagram
- I
R
X
}
}
R
LI
R
LI
R
LU
R
LU
+ U
- U
+ I
Introduction &
applications
Four-wire resistance measurement
If you have ever used a Thomson bridge, you must have noticed occasional interference
caused by supply-line resistances, though popular opinion has it that the influence of these
lines should be negligible.
Actually, it is negligible only as long as the line resistances do not exceed a certain, very low
limit; this applies particularly to the connection between the reference or standard resistance
R
N
(sketch) and the object under test R
X
.
An awkward side-effect of this is that resulting errors can go unnoticed.
RESISTOMAT
®
equipment incorporating the constant current/voltage drop technique does
not cause such problems.
Figure 1: Thomson bridge
R
L
can influence the result
