Kelvin test leads

Discussion in 'General Electronics Chat' started by apprentice, Jun 2, 2004.

  1. apprentice

    Thread Starter New Member

    Jun 2, 2004
    I have an agilent 34401a digital multi-meter.
    I need to use the 4-wire function for reading resistance in a sensitive PCB.
    Kelvin test leads are recommended but very costly and the aligator type clips are not conductive to the probing required.
    The data sheet on the kelvin clips state the jaws of the aligator clip must be isolated until they touch the component to be tested. That is how they are designed.
    I was hoping to create my own 4-wire test leads with probes on the end by twisting the raw end of one pair of wires together and soldering to a probe. What will I lose by doing this?
    Will using a double banana jack converging to a single banana at the point on the test equipment work also?
  2. beenthere

    Retired Moderator

    Apr 20, 2004

    Gonna have problems. Kelvin measurement is picky. Using dissimilar metals, such as solder on wire joints, will mess the results. Seebeck effect will generate a small but significant voltage from such a joint.

    So will the use of non-copper alligator clips. There are tiny test lead connectors made for such purposes - I think they are known as "mini-grabbers". The contacts are copper, which should minimize the thermocouple effect. Some are small enough to get onto the legs of SOT devices.

    Good luck - good Kelvin measurements are just fussy.