A Design of Sensor Based upon Low Digital DC Current

Owing to the weakness, low susceptibility to interference and uneasiness to recover of DC signals, permalloy based upon high magnetic permeability is used as a magnetic material. The change of current is transformed into that of inductance with reference to the relationships among current I , intensity H of magnetic fields, intensity B of magnetic induction, rate of magnetic conduction of material and magnetic permeability μS. Hence we have designed the RL multivibrator with only one coil that is self-driven. The objective is to convert the change of induction into that of pulse width. With the technology of single-chip microcomputer, measurement of the width of high-speed pulse and data transmission based upon PROFIBUS, we have designed and produced all-digit DC sensor. We are expected to explain the working principles of sensors, introduce the method of hard ware circuit and discuss over the dominant errors in respect of signal processing. The sensor is characteristic of compactness, high precision, strong anti-interference, easy extension, etc. Through the test of the current ranging from 0.05 mA to 10 mA, the error is less than 5 percent and resolution is less than 0.05 mA. The sensor can meet the current situation of use.