Design Of Rotational Speed Sensor Based On The Pirnciple Of Eddy Current

In this paper, the of the rotational speed sensor designed is a sensor basedon eddy current effect, by a sensitive probe, converter and extension cable, withthe small probe size, long measuring distance, wide working temperature range,fast response, resistance to harsh environment, stable performance, convenientinstallation, strong universality etc.. The sensor uses coils as the sensingelement, through the processing of subsequent measurement circuit istransformed into (0~5)V square wave output. This paper mainly completed thedesign, manufacture and test of the sensor, and the test results were comparedand analyzed, experimental results show that the sensor’s performance to meetthe use requirements.In the basic theory of eddy current sensor, focuses on the principle of eddycurrent effect and eddy current sensor, based on the theoretical analysis of therelationship between the eddy current intensity and the measuring distance andfrequency input, and the influencing factors of the characteristics of the sensor.In the basic theory of soft magnetic materials, introduces the basic theoryof soft magnetic ferrite, high permeability ferrite cores and high permeabilityMn-Zn ferrite research present situation, and the basic electromagneticproperties of Mn-Zn ferrite material is described.In the design of eddy current rotational speed sensor, introduces the designof the sensor’s structure, the sensitive probe and the subsequent processingcircuit, this paper analyzes the technical difficulties and solving measures ofsensitive coil designed, were studied to determine the coil arrangement andgeometric size, the design of external processing circuit to convert the electricalsignal of the sensitive coil. Found in the study of sensor system debugging andtesting, rotational speed measurement using the eddy current sensor, it’s notaffected by temperature in the whole temperature range, the maximum deviationis less than1%in the range of100℃~150℃, the temperature stability is better.In this paper, through the study of sensitive coil of sensor probe and the circuit,knowing well that the relationship between eddy current intensity and coil parameters ofsensor probe, measuring distance, and its influence on the measurement of rotational speed, and the technology of weak signal pickup, amplification, conversion, realize themeasurement mode of rotational speed, that small area measured and long measuringdistance in the harsh environment of wide temperature range.