Torsional Balance for Simultaneous Evaluation of Thrust Force and Flow Velocity of Electrostatically Induced Ionic Wind

This paper describes the development of a precise thrust measuring balance based on torsional pendulum principle for simultaneous evaluation of thrust force and flow velocity of electrostatically induced ionic wind. The balance has achieved a resolution as low as 1.38~\mu \text{N} and zero drift of 0.15 nN/s through proper isolation of external noises. Calibration has been carried out by using an improved version of electrostatic calibrator which produces a wide range of accurate and repeatable calibration force. After the calibration, the balance can resolve constant force from 41.03 to 627.84~\mu \text{N}. The maximum uncertainty error is 12.90% for measurement of constant force. The application of the balance has been demonstrated in measuring the smallest thrust force of 62.2~\mu \text{N} produced by the ionic wind. Using jet impingement theory, the lowest flow velocity of the ionic wind is evaluated as 27 m/s.