Capacitive Sensor Based On Active Bridge Circuit And Its Measurment System

The characteristic, type and measurement principle of capacitive sensor have been expounded. The systematic research to measurement circuit have been carried on especially. An active bridge circuit that is suitable for measuring accurate electric capacity has been designed after the Wheatstone bridge circuit has been improved according to its existing shortcoming. Through joining the reverse amplifier with adjustable multiple in the arm of a bridge, it make the parameter is very easy to adjusted and realize the linear output at the same time. The theory and experiment indicate: This circuit performs high sensitivity and good linearity.Applying the active bridge circuit to nonmetal dielectric medium measurement, the capacitive moisture measurement system for grain has been designed and realized according to existing problem of the moisture measuring. The cylindric type capacitive sensor was selected to as sensitive probe. The research on the working frequency, standard method and...