Degrees of Kelvin
Many test and equipment manufacturers use connections to the device under test which are not in fact 'true' Kelvin, but 'semi' Kelvin. This can best be illustrated in Figure 3a, where 'spring' probes are used. It can be seen that the spring probe does not provide a true Kelvin connection, as the four wires are terminated at the probe receptacle.
In order to be 'true' Kelvin, each 'power' and 'sense' lead needs to make the connection directly to the test component lead and as close as possible to the test component itself.