The static state analysis of the balance suspension system for its displacement measuring

In order to precisely measure the displacement of the coil suspension system of the Joule Balance in the static state, we give a detailed analysis about its influence factors in this paper. We designed a dual-frequency laser interferometer system to measure the movement of the coil suspension in vertical direction. And a supporting device was designed to support the coil for the aim to make it more stable. The result showed that the coil suspension system is affected by ground vibration, temperature drift, stress release, pendulum swing. The drift of the coil suspension is about 120 nm among 3 minutes without supporting device, the data is greatly reduced after we support it.