Abstract: The plate non-parallelism error of capacitance displacement sensor is studied to improve the thrust measurement accuracy of space-borne micro-thrusters. The relation between the plate non-parallelism error and variable torsional angle is analyzed by taking a typical torsion balance for example. Based on the property of that the plate non-parallelism error and width cosine error are all independent of the direction of torsional angle, a calibration method is presented, and an experimental instrument is designed. A sensor with range of 1 mm and effective radius of 3.5 mm is calibrated with an increment of 0.5°, and the deviation between the non-parallelism error and its theoretical value is 17.4%. The calibrated results show that the measured thrust error derived from non-parallelism error is rapidly increased to 3.25% when the steady-state torsional angle gets close to the maximum negative angle; and it is gradually increased to 0.04%, corresponding to the measured thrust error of 0.1 μN, when the steady-state torsional angle gets close to the maximum positive angle; the effective radius of plate is not more than 7 mm when the measured thrust error is less than the order of magnitude of μN.Key

Key words: space-bornemicro-thruster, thrustmeasurement, displacementmeasurement, platenon-parallelismerror, experimentalcalibration