Link Compensation in the Kelvin Bridge

Compensation for the effects of large link resistance in bridge measurement of four-terminal resistors usually requires high precision in the adjustment of the compensating ratio arms. This paper describes an alternative method which requires no change in the normal balance procedures and is inexpensive to implement using readily available operational amplifiers. A description of a particular measurement at the part-per-million level of a 10-Ω resistor with a link of 200 Ω is given. Practical circuit details are included.