Improvement of a Uniaxial Seismic Accelerometer, an Integral Part of the Three-Axis Seismic Accelerometer SEM (ExoMars Seismometer)

Abstract

A three-axis seismic accelerometer was developed and created, containing three uniaxial mutually perpendicular sensors, the sensitivity axis of each sensor is located at an angle of 54.736° to the local gravitational vertical. For the first time, additional magnetic rigidity has been introduced into each device, allowing the device to be finely tuned to the conditions of a particular planet. However, the accumulated experience in conducting ground-based tests has shown the need to improve the uniaxial seismic accelerometer, which can significantly improve the characteristics of the device. First, we use a single material—beryllium bronze BrB-2—for the manufacture of massive test mass suspension elements with a thickness of 1.5 mm and an elastic element made of a thin strip 10–20 microns thick, which reduces the likelihood of instability. Secondly, we reduce the gap in the capacitors of capacitive converters from 0.25 to 0.1–0.15 mm to significantly increase the conversion slope of the capacitive sensor. Thirdly, we change the technology of setting up the device, for which we combine all the elements of the sensitive part of a uniaxial seismogravimeter using special vertical inserts. This allows us to place the device as a whole in a system for its configuration, eliminating the possibility of failure of individual elements, thereby increasing the reliability of the device.