Four-Lead Measurement of Resistance

The advantage of this method involves controlling the flow of current through all the connections – especially those used to measure the voltage. The measurement current flows through one set of connections, usually those that are farthest apart. If these connections are resistive (i.e., the connections are poor) there will be significant voltage drop across them. However, this voltage drop doesn’t matter as long as the power supply has a sufficiently high output voltage since the only parameter in which we are interested for these connections is the actual current flowing through the object. This current is being accurately measured by the ammeter in series between the object and the current source.