A Kelvin connection is a way to make electrical potential contact with a current carrying component with slightly influencing the effect of contact resistance. It is especially important when dealing with low millivolt measurements. The best means is to use a 4-terminal device in which two terminals conduct the high current, while the other two are used expressly for measuring voltage. When working with two terminal devices, clip leads are sometimes connected as close as possible to the resistance element for measuring the potential—these are referred to as “Kelvin clips.” In this case, clip leads are used for making temporary measurements, but a two lead device may be converted to a 4-lead device simply by replacing the clips with soldered leads.
To eliminate the effect of lead resistance in high current power supplies which can cause voltage drop, separate sense voltage terminals connect directly to the external load for the purpose of voltage feedback. Suppose we have 4 terminals; 2 for power and 2 for sense. This is a common feature in high current, low voltage power supplies. The sense leads conduct very low current so the sense lead resistance does not add significant voltage error.