CN-115856433-B - Dual-AC bridge impedance separation detection circuit and detection method

CN115856433BCN 115856433 BCN115856433 BCN 115856433BCN-115856433-B

Abstract

The invention provides a double-AC bridge impedance separation detection circuit and a detection method, wherein a first connecting end of a first AC bridge is respectively connected with one end of a voltage source and a first connecting end of a second AC bridge, a second connecting end of the first AC bridge is connected with one end of a first balancing resistor R s1 , a third connecting end of the first AC bridge is connected with one end of a second balancing resistor R s2 , the other end of the first balancing resistor R s1 is respectively connected with the other end of a second balancing resistor R s2 , the other end of the voltage source, one end of a third balancing resistor R s3 and one end of a fourth balancing resistor R s4 , a second connecting end of the second AC bridge is connected with the other end of a third balancing resistor R s3 , and a third connecting end of the second AC bridge is connected with the other end of the fourth balancing resistor R s4 . The invention can accurately separate the impedance and inductance variation of the wide-range eddy current displacement sensor in the detection process, and more accurately measure the displacement between the eddy current probe and the target.

Inventors

WANG KUNDONG
YUAN JIE
LI BAIMING
LEI HUAMING
CAI PING

Assignees

上海交通大学

Dates

Publication Date: 20260512
Application Date: 20221122

Claims (8)

1. The double-alternating-current bridge impedance separation detection circuit is characterized by comprising a reference bridge, a measuring bridge and a voltage source which are connected in parallel, wherein the reference bridge comprises a first alternating-current bridge, a first balancing resistor R s1 and a second balancing resistor R s2 , and the measuring bridge comprises a second alternating-current bridge, a third balancing resistor R s3 and a fourth balancing resistor R s4 ; The first connecting end of the first alternating current bridge is respectively connected with one end of the voltage source and the first connecting end of the second alternating current bridge, the second connecting end of the first alternating current bridge is connected with one end of the first balancing resistor R s1 and is used as a first detection end, and the third connecting end of the first alternating current bridge is connected with one end of the second balancing resistor R s2 and is used as a second detection end; the other end of the first balancing resistor R s1 is respectively connected to the other end of the second balancing resistor R s2 , the other end of the voltage source, one end of the third balancing resistor R s3 and one end of the fourth balancing resistor R s4 , and is grounded; the second connecting end of the second alternating current bridge is connected with the other end of the third balancing resistor R s3 and is used as a third detection end, and the third connecting end of the second alternating current bridge is connected with the other end of the fourth balancing resistor R s4 and is used as a fourth detection end; The measuring bridge and the reference bridge are switched through an analog switch; The inductance of the bridge at the balance position is L, and the resistance values of the first balance resistor and the second balance resistor exceed Is a factor of 15 of the number of (c), Where ω is the angular frequency, ω=2pi f, f is the operating frequency of the voltage source, When the switch is switched to the reference bridge, the output voltage phase of the reference bridge is: ; Wherein, gamma is the phase angle of numerator in the output voltage signal formula of the bridge, gamma' is the phase angle of denominator in the output voltage signal formula of the bridge, L is the amount of change in inductance L of the sensor relative to the initial bridge equilibrium position, R is the variation of the alternating current resistance R of the sensor relative to the initial bridge balance position; when the switch is switched to the measuring bridge, the output voltage phase of the measuring bridge is: 。
2. The dual ac bridge impedance separation detection circuit of claim 1 wherein the voltages output from said reference bridge and said measurement bridge have a phase difference that is independent of resistance, effecting impedance separation, The detection signal is the phase difference between the measuring bridge and the reference bridge, which is only related to the inductance.
3. The dual ac bridge impedance separation detection circuit of claim 2 wherein the voltages output from the reference bridge and the measurement bridge are demodulated by a lock-in amplifier.
4. A dual ac bridge impedance separation detection circuit according to claim 3 wherein the real part of the output voltage is obtained using a reference signal at a 0 degree phase angle and the imaginary part of the output voltage is obtained using a reference signal at a 90 degree phase angle.
5. The dual ac bridge impedance separation detection circuit of claim 4 wherein the phase difference between the reference bridge and the measurement bridge output voltage is obtained by algebraic operation of the real and imaginary parts of the reference bridge and the measurement bridge output signal.
6. A sensor displacement and temperature detection method is characterized in that, the double-alternating-current bridge impedance separation detection circuit based on any one of claims 1 to 5, comprising the steps of: The double alternating current bridge comprises a bridge arm formed by an eddy current probe, a reference arm formed by coils with the same specification as the eddy current probe or common equivalent inductance resistance, In a preset temperature range, the alternating current resistance value of the eddy current probe coil correspondingly increases along with the rising of the temperature, a corresponding functional relation exists between the resistance value and the temperature, and the current environmental temperature of the eddy current sensor in a static state is measured by calibrating the functional relation; Step 2, the inductance of the eddy current probe is in an exponential relation with the measurement displacement of the target, and the relation between the sensor probe displacement and inductance change is calibrated by calibrating the coefficient of the exponential relation, so that the target movement displacement is measured; Step 3, under the condition of different temperatures, the index relation coefficients calibrated in the step 2 are different, the real target displacement and inductance change functional relation under the current environment temperature is determined by combining the step 1 and the step 2, the index coefficients of the sensor displacement and the detection signals with unique corresponding relation with the inductance change are calibrated, and the real displacement value without temperature drift under the current environment is obtained; and calibrating the displacement relation between the detection signal and the sensor under different temperature conditions to obtain a real displacement value without temperature drift.
7. The sensor displacement and temperature detection method according to claim 6, wherein in the step 1, the change in the detection signal represents a change in temperature, and the phase difference thereof is represented by the real part and the imaginary part of the two-point bridge output voltage as: ; wherein R s is the balance bridge resistance of the first AC bridge, R is the AC resistance of the sensor probe at the initial balance position of the bridge, For a vector consisting of the real and imaginary parts of the output voltage from the first ac bridge, Is a vector composed of the real part and the imaginary part of the output voltage from the second ac bridge.
8. The sensor displacement and temperature detection method according to claim 6, wherein in the step 2, the change of the detection signal represents a change of inductance, and the phase difference thereof is represented by a real part and an imaginary part of the output voltage of the two-point bridge: 。

Description

Dual-AC bridge impedance separation detection circuit and detection method Technical Field The invention relates to the technical field of detection circuits of wide-range eddy current displacement sensors, in particular to a double-alternating-current bridge impedance separation detection circuit and a detection method, and especially relates to a double-alternating-current bridge impedance separation detection circuit for a wide-range precise eddy current sensor. Background The signal demodulation circuit aims to accurately measure the value of impedance or inductance along with the change of distance, and the advantages and disadvantages of the signal demodulation circuit directly determine the performance of the sensor, so that the signal demodulation circuit is the most important link in the sensor. Ac bridges are the most commonly used impedance measurement circuits, commonly found in strain gauge measurement circuits, however in eddy current sensor detection circuits, the resistance detects a parasitic parameter of the signal that needs to be controlled as much as possible, while the inductance is distance sensitive and temperature insensitive. In addition, according to the previous research, the variation of the inductance of the eddy current sensor at different positions can be well fitted by an exponential function, so that the variation of the inductance only needs to be obtained in the measurement process of the eddy current displacement sensor. The traditional AC bridge related in the eddy current displacement sensor detection circuit is a detection circuit which is improved based on the most basic AC bridge, and the circuit separates the inductance and the resistance of a detection signal. The bridge inputs an alternating current voltage source of 5V and 1MHz, the output voltage U is an expression about inductance change and resistance change, wherein the real part of the output voltage represents inductance change quantity, the imaginary part represents resistance change quantity, and the two can be separated through phase sensitive detection, and the key precondition of the inductance and resistance separation method is that the change quantity of inductance and resistance is far smaller than that of the bridge during operation, namely R > > [ delta ] R, L > > [ delta ] L. The eddy current displacement sensor has small measuring range, and the change of inductance and resistance is small during operation, so that the eddy current displacement sensor meets the conditions. However, the design of a wide-range eddy current sensor cannot ensure that the conditions R > >. DELTA.R and L > >. DELTA.L are satisfied when the sensor probe is far from the equilibrium position. The patent document with publication number CN106093577A discloses an impedance quick comparison measuring method and a measuring circuit, the method is based on the traditional AC bridge technology, two arbitrary signal generators are adopted as two serial digital sources, arbitrary vector voltage ratio is realized, and two serial compared impedances and two digital sources form a four-arm bridge. However, the patent document still has the defect that the variation of inductance and resistance is far smaller than that of the patent document when the patent document works. The patent document with the publication number CN103529268B discloses an alternating current bridge with an automatic auxiliary balance function and an impedance measurement method thereof, wherein the alternating current bridge comprises an alternating current power supply, a main inductive voltage divider, an auxiliary inductive voltage divider and a zero indicator, the main inductive voltage divider and the auxiliary inductive voltage divider have the same inductive voltage division ratio, a negative feedback branch consisting of an active voltage follower, a reverse amplifier, a filter and an isolation transformer which are connected in series is arranged between the main inductive voltage divider and the auxiliary inductive voltage divider, the primary side of the isolation transformer is connected with the auxiliary inductive voltage divider, the input end of the active voltage follower is connected with the main inductive voltage divider, the output end of the active voltage follower is connected with the zero indicator, and the measurement method is that the zero indicator branch automatically obtains the ground potential after the partial voltage on the main inductive voltage divider is processed by the negative feedback branch, and the bridge can realize impedance comparison measurement through simple main balance. However, this patent document is different from the present application. Disclosure of Invention Aiming at the defects in the prior art, the invention aims to provide a double-alternating-current bridge impedance separation detection circuit and a detection method. The invention provides a double-alternating-current bridge impedance separat