The abnormal friction and abrasion of aircraft engine will produce a large amount of abrasive particles in lubricating oil

effective detection of lubricating oil abrasive particles can provide reliable information for engine fault diagnosis. An arc plate capacitance sensor is designed

but the capacitance change of sensor is very small

it is difficult to detect with traditional method

alternating current bridge capacitance detection method is used here.The system takes the AD9833 as DDS signal generator to exert pumping signal on alternating current bridge

by C /V conversion

differential amplifier

phase sensitive demodulation and low pass filtering obtain real time change of voltage. The design can realize accurate detection of weak signal

and it can overcome influence of stray capacitance and parasitic capacitance effectively. Multiple experimental results show that the system has characteristics of high sensitivity and good stability.