Research On Micro-power High-speed Long-distance Non-magnetic Sensor

In the design of flow meters such as smart water meters and gas meters,non-magnetic sensors have long been used in the past.The magnetic sensors to using magnetic devices such as Hall devices or reed switches to collect flow signals.Non-magnetic sensors have many shortcomings,such as magnetic loss,easy adsorption of impurities,complex structure,etc.,while non-magnetic sensors can solve these problems better,and it can adapt to more demanding measurement environments,and have higher measurement accuracy and reliability.The wide-voltage,high-speed,low-power non-magnetic sensor introduced in this article is a non-magnetic speed sensor,which mainly relies on the rotation count of the impeller.The inductance probe is close to the metal mark on the impeller and the sense value changes,and the LC oscillator completes the frequency modulation wave modulation.The demodulation is completed subsequently,and the signal is output in the form of a pulsed square wave.The overall structure of the circuit is composed of four parts:LC oscillator,integrating circuit,envelope discriminator circuit,and output circuit.The inductance of the LC oscillator is used as a probe.This article mainly analyzes its working principle and conducts in-depth research on the core part of its circuit envelope detection circuit,which provides a theoretical basis for future circuit improvement and application expansion.This article mainly carried out the following work:1.Made an overall introduction to the sensor circuit and sub-modules to study its working principle.The circuit analysis is guided by the flow of the signal.The overall principle of the circuit is the modulation and demodulation of the FM wave.In the first part of the circuit,the LC oscillator completes direct frequency modulation by changing the inductance of the inductance caused by the change of the impeller speed;the second part of the RC integrator circuit converts the frequency modulation wave into an amplitude modulation frequency modulation wave;the third part of the envelope amplitude discriminator circuit completes the discrimination amplitude,and output pulse square wave without high-frequency components;the fourth part of the push-pull output improves the load capacity of the circuit.2.Analyzed the envelope detection circuit and deeply explore the state reversal process.On the basis of typical Schmitt trigger,the acceleration capacitor and the transistor emitter to ground capacitance are added to the circuit,which can directly control the pulse turnover sensitivity and backlash.Based on the experimental research,this paper theoretically analyzed and verified the working principle and internal process of the core circuit by establishing a mathematical model.3.Improved the performance of the single-probe circuit,and discussed two options for judging the direction of rotation.This paper introduced the single-probe scheme that relies on the specially designed impeller to realize the judgment of forward and reverse rotation and the dual-probe scheme that uses the phase difference to judge the direction of rotation.Designed a basic dual-probe sensor circuit to adapt to a wider detection environment and promote to more application fields.