Abstract: SS-Y extensometer has been installed and used for many years in the crustal deformation observation. In order to ensure the observed signal-to-noise ratio, the length of the extensometer is generally between 10~30 m. The long baseline causes the instrument easy to be influenced by environmental interference. At the same time, due to the lack of sealed design, problems such as error of calibration may occur during long-time use. In order to solve these problems, this paper developed a new short-baseline extensometer. The instrument has a baseline length of 1 m. It uses a high-precision capacitive sensor for displacement measurement and a new overall sealing structure, which makes the instrument have a certain anti-interference ability. Through the linearity, sensitivity and other parameter tests and observation tests, it shows that the instrument has good performance characteristics and observed signal-to-noise ratio under the condition of short baseline, which lays a foundation for further optimization of the instrument.

Key words: Short baseline, Extensometer, Environmental interference, Anti-interference ability, Signal-to-noise ratio