The Exploration Research To Ultramicro-Force Measurement Using Electrostatic Field

With the development of ultramicro-force sensor, the performance of ultramicro-force sensor remains a challenge. Obviously, the construction of steady and accurate ultramicro-force measurement system is essential.In this paper, ultramicro-force measurement system based on electrostatic field was constructed and evaluated. The design work on mechanism, electric circuit and software was completed. That is, the experimental platform for pre-measurement system was set up. Trials about systematic drift, calibration, repeatability, resolution, linearity as well as the capacitance gradient measurement and electrostatic force verify experiment was done. The major work was summarized as follows:According to the electrostatic force generation principle, ultramicro-force measurement scheme using electrostatic field method was designed. The measurement system works in two continuous measurement modes. In mode one, the system completes the measurement of capacitance gradient and in mode two, it completes the measurement of ultramicro-force.Self-designed electrostatic force generator was adopted in the measurement system. Considering that cylindrical capacitance offers several advantages including the wide operating range, superior in linearity and little edge effect, it became the best choice of capacitance sensor. The using of spring hanging structure and coaxiality adjustment mechanism eliminates the friction between outer electrode and inner electrode. The spring hanging structure also generates the utramicro-force in the electrostatic force generation experiment.Capacitance acquisition module based on high-precision integrated capacitance-to-digital converter AD7747 and USB control chip FX2LP was designed. The whole module contains the circuit, relative firmware and software. The capacitance gradient of electrostatic force generator can be measured using this module combined with high-precision capacitance micrometer.The system platform in two measurement modes was built. Trials about systematic drift, calibration, repeatability, resolution, linearity as well as the capacitance gradient measurement and electrostatic force verify experiment were done in these two platform. According to the result of the experiment, the principle of electrostatic force generation and the ultramicro-force measurement scheme using electrostatic field method were verified. The above aspects of the work have laid a solid foundation of theory and practice for further exploration of 10-5N or smaller ultramicro-force measuring.