To meet the requirements of the differential expansion detections in the monitoring system of turbo-generator

the frequency conversion type and differential expansion eddy current sensor was developed.The working principles of frequency-modulated eddy current sensor is introduced.And according to the relationship between the measured displacement and frequency

a linear mathematical model has been carried out.The sensor measuring circuit has been designed

and related performance test of the frequency conversion type and differential expansion eddy current sensor has also been carried out.The advantage of this sensor is that it can output both frequency signal and voltage signal.The frequency output can effectively improve the ability of signal transmission anti-interference and make data collection and processing convenient

while the voltage output can make the amount of displacement be obtained directly.Field trial results show that the performance of the sensor developed is stable and reliable.The sensor has high resolution

precision and strong anti-interference ability.