For 4-pole measurements according to the Kelvin method, coaxially constructed spring contact probes are very suitable, where the outer conductors impress a current and the voltage can be measured by the inner conductors.
A typical application is the measurement of low impedance resistors, especially in narrow spaces.
Pointing Accuracy and Radial Tolerance
The pointing accuracy of a spring contact probe is determined by many factors, for example by manufacturing tolerances, by the length of the plungers and by the type of plunger guiding. Further factors that are independent of the contact probe have to be considered, for example the receptacles and the mounting of the test fixture or module. To optimize the pointing accuracy especially in applications with small centers additional guiding plates in the fixture can be used.
