Why Use a Kelvin Connection?

The four wire Kelvin Connection permits the precision measurement of low resistances without concern for lead length or contact resistance.  In a Kelvin Ohmmeter, a precision current source sends a measurement current through the component  using one pair of wires in the test leads.  The current carrying leads resistance can vary considerably, but the constant current source will send the same current through the test circuit.  With a known current passing through the tested component, there will be a voltage drop across the component that is proportional to the resistance there in.  In a Kelvin test, another pair of test leads are connected across the same component.  These leads are connected to a very high impedance DC volt meter.  The measured voltage again does not care at all about lead resistance or contact resistance until those values would rise to thousands of Ohms.  Because the current carrying circuit is completely separate from the voltage measurement circuit, a precise resistance can be measured, even to small fractions of an Ohm.

Can I run four wires and then use two test contacts?

Yes, you can, but then contact resistance will become part of your measured resistance.  This will not be a concern if you are measuring resistances of 100 Ohms or greater.  It is NOT EVER advisable at lower resistances.  Even a commercial Gold Plated 'Pogo Pin" can have a resistance of up to one Ohm after several thousand operations.  Where ever possible make four separate connections to the test component.

Must I purchase Kelvin Test Leads from Harris IRT?

Certainly not.  Our Meters will operate with any good Kelvin test lead set.   We realize that differnt components will require special solutions.  You may design your own solutions or you are welcome to ask us about solutions we may have already designed for others.  We are always here to help in any way we can, to make resistance accurate measurements under difficult situations.