CN-116626388-B - Inductance type sensor conditioning circuit based on LC resonance circuit

CN116626388BCN 116626388 BCN116626388 BCN 116626388BCN-116626388-B

Abstract

The invention provides an inductance sensor conditioning circuit based on an LC resonance circuit, which is characterized in that an inductance sensor is used as an inductor to form a resonance circuit with a capacitor, a sinusoidal resonance signal is generated by being connected into an active negative resistance circuit, and the frequency and the amplitude of the resonance signal are measured through a signal processing circuit. The invention can accurately measure the impedance change of the inductance sensor by the mode, and simultaneously realize the self-temperature compensation of the sensor by using measured data and an algorithm.

Inventors

WANG KUNDONG
LI BAIMING
YUAN JIE
LEI HUAMING
CAI PING

Assignees

上海交通大学

Dates

Publication Date: 20260512
Application Date: 20230519

Claims (8)

1. An inductance sensor conditioning circuit based on an LC resonance circuit is characterized by comprising the LC resonance circuit, an active negative resistance circuit and a signal processing circuit; the LC resonant circuit is used for selecting a specific frequency and keeping the frequency of a resonant signal stable; The active negative resistance circuit is used for supplementing energy consumed in the LC resonant circuit and maintaining signal resonance; The LC resonant circuit is connected in parallel with the active negative resistance circuit to generate a resonant signal, the signal processing circuit measures the amplitude and the frequency of the resonant signal, so as to demodulate the impedance change of the sensor, and then the measured value is measured more accurately and the self-adaptive temperature compensation is carried out according to the relation between the measured value and the temperature and the relation between the impedance of the sensor; The signal processing circuit comprises a frequency measuring circuit and an amplitude measuring circuit, wherein the frequency measuring circuit and the amplitude measuring circuit are of parallel structures and respectively measure frequency information and amplitude information in a resonance signal; The amplitude measuring circuit comprises a precision detection circuit, a low-pass filter, an F/V conversion circuit or an A/D converter which are connected in series, wherein the precision detection circuit is used for full-wave rectifying a resonance signal, the low-pass filter is used for filtering the rectified signal into a direct-current voltage signal, and the F/V conversion circuit or the A/D converter is used for converting the direct-current voltage signal into a digital signal, so that the amplitude of the resonance signal is measured.
2. The LC-tank based inductive sensor conditioning circuit of claim 1, wherein the LC-tank includes an inductive sensor and a capacitor in parallel; the inductive sensor is used for converting non-electric quantity in the environment into sensor impedance change; the capacitor and the inductive sensor form an LC resonant circuit for assisting in adjusting the frequency range of the resonant signal.
3. The LC-resonant circuit based inductive sensor conditioning circuit of claim 2, wherein the equivalent series inductance of the inductive sensor is The equivalent series resistance of the inductive sensor is The capacitance of the capacitor is The equivalent series resistance of the capacitor is The LC resonant circuit can be equivalent to parallel inductance due to impedance change Parallel capacitor Parallel resistor The parallel configuration has the following values: In the formula, Is the quality factor of the inductance branch, and has the value of ; Is the quality factor of the capacitor branch, and has the value of ; Is the angular frequency of the signal, at the resonant frequency Parallel inductor Parallel capacitor Will cancel each other out when the equivalent output impedance is 。
4. An LC-tank based inductive sensor conditioning circuit according to claim 3, wherein the active negative resistance circuit is composed of an active device and a resistor for compensating the energy dissipated by the resistor in the LC tank so that the signal in the LC tank remains oscillating, wherein the active negative resistance circuit is equivalent to a negative resistance An active negative resistance circuit is connected in parallel with the LC resonance loop In the time-course of which the first and second contact surfaces, And The parallel resistance formed is infinite and, And An ideal LC tank is formed, and the impedance in the LC tank is always 0.
5. The LC-resonant circuit based inductive sensor conditioning circuit of claim 4, wherein the active negative resistance circuit is built up from a colpitts circuit and a cross-coupling circuit using active devices including transistors, MOS transistors and operational amplifiers.
6. The LC resonant circuit-based inductive sensor conditioning circuit of claim 1, wherein the frequency measurement circuit comprises a hysteresis comparator in series with a digital frequency meter, the hysteresis comparator converting the resonant signal into an equal frequency square wave signal and then inputting the square wave signal to the digital frequency meter for measuring the frequency of the square wave signal.
7. An LC-tank based inductive sensor conditioning circuit according to claim 3, wherein when the quality factor of the capacitor is higher than that of the inductive sensor and the LC tank is operating in the current confinement region, the frequency of the resonant signal is determined by And amplitude value The information reflects the impedance change of the sensor, and the specific relation is as follows: Wherein, the Is a bias current set in the active negative resistance circuit.
8. The LC-resonant circuit based inductive sensor conditioning circuit of claim 7, wherein for an inductive sensor, measured And temperature The change causes sensor impedance And With monotonicity, and as can be seen from equations (4) and (5), when the impedance of the inductive sensor changes, the frequency of the resonant signal thereof And amplitude value With monotonous change, so the measured frequency And amplitude value Is about to be measured And temperature Expressed as a polynomial: The inverse function is expressed as: Wherein, the 、、、 Is a linear fitting coefficient, and is more than or equal to 1 ≤M;1≤ N is less than or equal to the number of measured changes, M is the number of temperature changes; From the following components Form column vectors By the following constitution And Form column vectors And By measuring processes And Compensating the measurement result by calibration And Given that K measurements are obtained in total, there are: The optimal estimation of the coefficient vector is obtained by the least square method: Wherein, the Is a vector of , ,..., A matrix of components.

Description

Inductance type sensor conditioning circuit based on LC resonance circuit Technical Field The invention relates to the technical field of inductive sensor detection circuits, in particular to an inductive sensor conditioning circuit based on an LC resonance circuit. Background An inductive sensor is an electromechanical conversion device which converts non-electric quantity in the environment into sensor inductance change based on an electromagnetic induction law, and a signal conditioning circuit is further required to convert the inductance into signals which can be directly identified, such as voltage, frequency and the like. The conditioning circuit can be divided into two methods of amplitude conditioning and frequency conditioning according to the difference of information of which inductance is modulated by the conditioning circuit. The amplitude conditioning connects the inductance coil of the sensor to the bridge or the voltage dividing circuit, and then converts the impedance change of the sensor into a voltage value or other electrical signals through the voltage dividing relation of the high-frequency signals. The frequency conditioning is to take the sensor coil as a resonant circuit formed by a resonant inductor and a capacitor, and the output frequency of the circuit signal directly reflects the equivalent inductance of the sensor. The most commonly used voltage amplitude conditioning method is a synchronous detection mode, the method is widely applied, the research and development are rapid, and most commercial circuits in the market almost use the technology. However, synchronous detection is also limited in high resolution measurement, which requires that after demodulation unit, the dc component in the demodulated signal is extracted by a filter or spectral analysis. If a low-pass filter is used for extracting the direct current component, the passband width of the low-pass filter directly determines the size of noise remained after the filtering, so that the contradiction between the dynamic response and the resolution of a measurement system occurs, and if a digital device is used for spectrum analysis, the resolution and the dynamic response can be ensured at the same time, but the additional high-cost device is added, and meanwhile, the A/D conversion rate is also required to be higher, so that the system cost is further increased. Patent document CN114440751a (application number: CN 202210067606.1) discloses a pulse width detection circuit and an inductance type displacement sensor, which comprises an oscillation circuit, a coil resonance circuit and a modulation circuit, wherein the output end of the oscillation circuit is connected with the input end of the coil resonance circuit, the output end of the coil resonance circuit is connected with the modulation circuit, the oscillation circuit is used for generating a driving square wave signal and outputting the driving square wave signal to the coil resonance circuit, the coil resonance circuit is used for generating a sine wave signal with the same frequency as the driving square wave signal and outputting the sine wave signal to the modulation circuit, and the modulation circuit is used for converting the sine wave signal into a pulse width modulation signal with the pulse width proportional to the displacement to be measured. However, the patent does not measure the frequency and amplitude of the resonant signal, and the impedance variation under the full scale condition cannot be accurately obtained. Disclosure of Invention In view of the drawbacks of the prior art, an object of the present invention is to provide an inductive sensor conditioning circuit based on an LC resonant circuit. The inductance type sensor conditioning circuit based on the LC resonance circuit comprises an LC resonance circuit, an active negative resistance circuit and a signal processing circuit; the LC resonant circuit is used for selecting a specific frequency and keeping the frequency of a resonant signal stable; The active negative resistance circuit is used for supplementing energy consumed in the LC resonant circuit and maintaining signal resonance; The LC resonant circuit is connected in parallel with the active negative resistance circuit to generate a resonant signal, the signal processing circuit measures the amplitude and the frequency of the resonant signal, so as to demodulate the impedance change of the sensor, and then the measured value is measured more accurately and the self-adaptive temperature compensation is carried out according to the relation between the measured value and the temperature and the relation between the impedance of the sensor. Preferably, the LC resonant tank includes an inductive sensor and a capacitor connected in parallel; the inductive sensor is used for converting non-electric quantity in the environment into sensor impedance change; the capacitor and the inductive sensor form an LC resonant circuit for assistin