For very accurate DC measurements, a semiconductor device test socket pin or many pins may require a force and a sense pin to contact a single test device pin.  This is a Kelvin connection and compensates for loss in the test channel. 

Signal Integrity can place Kelvin contacts at 0.25mm force to sense separation on either LGA or Ball grid array pins.  Pins for QFNs or QFPS may be separate fine pitch pins or one of our specially designed Kelvin pin pairs.

Kelvin Contact Test Socket 0.25mm Pitch