Abstract: Now the resistor with calculable AC/DC differemce which is the standard of AC resistor traceability at home and abroad has several types , such as the coaxial type，the quadrifilar type, the octofilar type and the bifilar type. These resistors are usually four-terminal-pair structure. The definition of the four-terminal-pair is the most strictly. Its electromagnetic fields exist in the cylinder body, and do not radiate outside. So the AC resistance measuring meter and the bridge adopt measurement principle of the four-terminal-pair. A four-terminal-pair coaxial resistance with calculable AC/DC difference is introduced. A mathematical model is established, the AC/DC difference and the time constant are calculated. Bg test and comparison, the time constant is verified.

Key words: Four-terminal-pair, AC/DC difference, Coaxial resistance, Time constant