In both the BVD method and the DCC method, at balance no current flows in the
measuring leads. Lead resistance is therefore unimportant when using four terminal
connections. In the potentiometric method resolution and accuracy are limited by (and
cannot be better than) the stability of the DVM detector. The BVD bridge method
suffers from the disadvantage that when scaling resistors in decade steps the same
current must be passed through both resistors and the greatest power is dissipated in
the largest resistor. This limits the dynamic range for sub ppm measurements for the
BVD to 1000 ohms and higher. In the DCC method the greatest power is dissipated in
the smallest resistor and the dynamic range for sub ppm measurements is limited by
the current noise of the DCC comparator to 10,000 ohms and less. The DCC method
also suffers from the disadvantage of using 2 terminal measurements above 10,000
ohms.