CN205642275U - High dynamic response eddy current displacement sensor of wide range high accuracy - Google Patents

Abstract

The utility model discloses a large-range, high-precision, and high-dynamic-response eddy current displacement sensor, which comprises an AC resonant step-up bridge, an amplitude stabilization circuit, an amplitude compensation and addition circuit, an orthogonal sampling trigger signal generation circuit, and a high-speed sampling processor; The AC resonant step-up bridge is composed of a resonator, a resistor (R2) connected in parallel with the resonator, and a capacitor (C1) and a resistor (R1) connected in series with the resonator; the resonator is composed of an inductance probe (Lx), Composed of two series capacitors (C2, C3); the amplitude stabilization circuit consists of a variable gain amplifier (4), a synchronous detection circuit (3), an amplitude averaging circuit (6) and a comparison regulator (7); amplitude compensation and addition The circuit is composed of operational amplifiers and resistors; the quadrature sampling trigger signal generation circuit is composed of a high-speed comparator, and the comparator is provided with two input terminals, one of which is connected to the output terminal of the synchronous detection circuit (3), and the other terminal Enter the DC voltage (S_ut).

Description

A Large Range High Precision High Dynamic Response Eddy Current Displacement Sensor

technical field

The utility model relates to an eddy current displacement sensor, in particular to an eddy current displacement sensor with large range, high precision and high dynamic response.

Background technique

The basic principle of this type of sensor is that when the coil emitting the alternating electromagnetic field is close to the metal, there will be an eddy current effect. The closer the distance between the coil and the metal surface, the greater the loss. When other factors remain unchanged, the distance between the sensor and the metal surface can be measured by measuring the loss.

At present, the linear range of the eddy current displacement sensor is only half of the probe diameter; within the measurement range, the output signal of the inductance probe has a small variation range and low sensitivity; the absolute value detection of the diode is adopted, and the anti-interference is low; and a large number of internal integrated Analog devices cause severe temperature drift and complex systems.

Contents of the invention

In order to solve the above-mentioned technical problems, the purpose of this utility model is to provide a large range, high precision and high dynamic response eddy current displacement sensor, the sensor is a high reliability, low temperature drift eddy current displacement sensor; the sensor is widely used in displacement, vibration measurement, also suitable for production line status monitoring.

The purpose of this utility model is achieved through the following technical solutions:

A large-scale, high-precision, high-dynamic-response eddy-current displacement sensor, comprising: an AC resonant step-up bridge, an amplitude stabilization circuit, an amplitude compensation and addition circuit, a quadrature sampling trigger signal generation circuit, and a high-speed sampling processor;

The AC resonant boost bridge consists of a resonator, a resistor (R2) connected in parallel with the resonator, and a capacitor (C1) and a resistor (R1) connected in series with the resonator; the resonator consists of an inductance probe (Lx), two Composed of series capacitors (C2, C3);

The amplitude stabilization circuit is composed of a variable gain amplifier (4), a synchronous detection circuit (3), an amplitude averaging circuit (6) and a comparison regulator (7);

Amplitude compensation and addition circuit, composed of op amp and resistor;

The quadrature sampling trigger signal generating circuit is composed of a high-speed comparator. The comparator is provided with two input ends, one of which is connected to the output end of the synchronous detection circuit (3), and the other end is input with a DC voltage (S_ut).

Compared with the prior art, one or more embodiments of the present invention may have the following advantages:

Using amplitude compensation technology, the output range of the sensor can be increased and the sensitivity can be improved;

A high-speed comparator is used to compare the amplitude of the synchronous detection signal B with stable amplitude, thereby generating a quadrature sampling trigger signal; this method has a simple structure and can reliably generate a quadrature sampling trigger signal (S_t) with a phase difference of 90 degrees;

The measuring probe coil is used in series with two capacitors, and excitation is input from both ends of a capacitor; under the same excitation voltage condition, compared with inputting excitation signals from both ends of the coil, the excitation voltage at both ends of the inductance coil can be significantly increased, and the measurement scope;

Using a high-speed comparator and a high-speed analog switch to form a synchronous detector, compared with an absolute value circuit composed of a diode, it has the advantages of fast speed, high precision and good stability;

The orthogonal sampling method with a phase difference of 90 degrees is used to reduce the sampling rate, and the impedance of the probe inductance coil can be easily obtained; at the same time, the method of digital signal processing is more stable than analog circuit signal processing, and the structure is simple. The advantage of easy refactoring.

When the sensor makes a measurement, the sampling number n can be adjusted, and adjusting the sampling number can change the dynamic response of the system; the smaller the sampling number n in each measurement, the higher the dynamic response, and because the excitation signal S1 of the acquisition bridge and The output signal S2 is used as the basis for measuring the displacement. The dynamic response of the sensor is not limited to the dynamic response of the amplitude stabilization circuit; the dynamic response of the system is only related to the sampling frequency and the number n of samples.

The method of using fitting polynomial to correct the temperature drift of the sensor is faster than the commonly used look-up table method, the storage capacity is smaller, and the frequency response performance of the sensor is improved.

Description of drawings

Figure 1 is a structural diagram of an eddy current displacement sensor with large range, high precision and high dynamic response;

Figure 2 is the amplitude stabilization circuit;

Figure 3 is the amplitude compensation and addition circuit;

Fig. 4 is a quadrature sampling trigger signal generating circuit;

Fig. 5 is the waveform of bridge signal (S1 and S2);

Figure 6a and 6b are the waveforms of the amplitude stabilization signal (A) and the synchronous detection output signal (B);

FIG. 7 is the waveform of the quadrature sampling trigger signal (S_t) and the synchronous detection output signal (B).

detailed description

In order to make the purpose, technical solutions and advantages of the utility model clearer, the implementation of the utility model will be further described in detail below with reference to the examples and drawings.

As shown in Figure 1, it is an eddy current displacement sensor with large range, high precision and high dynamic response. processor; the

The AC resonant boost bridge consists of a resonator, a resistor (R2) connected in parallel with the resonator, and a capacitor (C1) and a resistor (R1) connected in series with the resonator; the resonator consists of an inductance probe (Lx), two Composed of series capacitors (C2, C3);

The amplitude stabilization circuit is composed of a variable gain amplifier (4), a synchronous detection circuit (3), an amplitude averaging circuit (6) and a comparison regulator (7);

Amplitude compensation and addition circuit, composed of op amp and resistor;

The quadrature sampling trigger signal generating circuit is composed of a high-speed comparator. The comparator is provided with two input ends, one of which is connected to the output end of the synchronous detection circuit (3), and the other end is input with a DC voltage (S_ut).

A tap is set in the resonator included in the AC resonant boosting bridge, and the tap is set at both ends of the capacitor (C3).

The input terminals of the comparison regulator above are the output signal (C) and the reference voltage (S_ua) of the amplitude averaging circuit respectively.

In this embodiment, the amplitude compensation technology can be used to increase the output range of the sensor and improve the sensitivity. The reason is as follows: Assuming that the inductance probe is between the maximum and minimum measurement displacement, the value range of its loss resistance Rx is {R _x |R _min ≤R _x ≤R _max },

make Then the value range of K _rx is

It can be assumed

${\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; x</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>$

Then the value range of K _rx is {K _rx |K _{rx_min} ≤K _rx ≤K _{rx_max} };

Assuming that the bridge is excited at a steady amplitude (S1=A), the output (S2) range of the sensor is:

D _{ran_1} = A*(K _{rx_max} -K _{rx_min} ),

When the bridge has amplitude compensation, the compensation method is: S1=K*S2+A, and its output (S2) range is:

${\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; *</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>$

When K*K _rx <1,

$\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ></span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span>$

So D _{ran_2} > D _{ran_1} ,

Amplitude compensation technology can increase the output range of the sensor and also improve the sensitivity.

The inductance Lx above is the coil of the eddy current sensor probe, which emits a high-frequency electromagnetic field. When the coil is close to the metal surface, an eddy current effect occurs and eddy current loss occurs; and the closer the distance, the greater the loss. Resistor R1 is a proportional voltage divider resistor; resistor R2 is an attenuation matching resistor, and the attenuation ratio of the bridge can be adjusted by adjusting the resistance of R2; capacitors C2 and C3 are resonant capacitors; capacitor C1 is a DC blocking capacitor. The excitation signal of the bridge is S1, the output signal is S2, and the bridge and the external amplifier form a controllable self-excitation circuit. The self-excitation frequency is determined by the inductance of the probe Lx and the size of the capacitors C2 and C3. In the amplitude compensation and addition circuit: the input signal is composed of the resonator output signal S2 and the amplitude stabilization signal A, and the external controllable self-excitation circuit determines the magnitude relationship of the bridge signal: S1=K*S2+A, where "K " is the compensation coefficient, and A is the stable amplitude signal, which is the same frequency and phase as the bridge output signal S2. From the perspective of the AC bridge (C1, C2, C3, R1, R2, Lx) itself, if the voltage division system is K _rx , it can be obtained that S2=K _rx *S1; the size of S2 is determined by the external amplifier circuit and the AC bridge itself. The partial pressure relationship is jointly determined. The range and sensitivity of the eddy current displacement sensor can be expanded by using the method of amplitude compensation; however, the total gain of the loop (K*K _rx ) must be controlled within a range less than 1, otherwise the loop will lose control. At the same time, by changing the setting of the amplitude stabilization circuit, the amplitude of the amplitude stabilization superimposed signal can be modified, and finally the excitation signal S1 and the output signal S2 on the AC bridge can be changed.

The input signal of the above-mentioned variable gain amplifier comes from the output signal S2 of the bridge, and the output signal A is an amplitude-stabilized signal, which is realized by a closed-loop control network composed of synchronous detection 3 , amplitude averaging 6 , and comparison regulator 7 . The specific process is: synchronous detection is equivalent to taking the absolute value of the signal that needs to be stabilized; then performing amplitude averaging on the signal B that takes the absolute value, which is equivalent to converting the amplitude information of the stabilized signal into a DC voltage C; the voltage C and the given Compare with a given DC voltage S_ua, and make negative feedback adjustment, so that the average value of the absolute value of the output signal A is always equal to the given DC voltage S_ua, to achieve the purpose of stable amplitude.

In Figure 2, the high-speed comparator U7 is triggered at the zero-crossing point of the signal to form a square wave signal. The square wave signal controls the high-speed analog switch U5; when the input signal A is less than zero, the analog switch U5 outputs the inverse signal of signal A; the invert signal is realized by the inverting amplifier composed of operational amplifier U4A, resistors R11 and R15. Since the output is a reverse signal when the signal is less than zero, and the output is a positive phase signal when the signal is greater than zero, this realizes the operation of taking the absolute value of the input signal A.

In Figure 3, the operational amplifier U2A and resistors R3, R4, R9 and R12 form an amplitude compensation and addition circuit; the function is to compensate the bridge output signal S2 and add a fixed excitation signal A. The output of this circuit 1 is used as the excitation signal S1 of the AC bridge. One example is that when R3=5K, R4=10K, R9=5K, R12=10K, the signal output of S1=2*S2+A can be realized, which is quite The output signal S2 is amplified twice and then the amplitude-stabilizing signal A is superimposed as the excitation signal of the bridge; at this time, when the maximum voltage division coefficient K _rx of the bridge is close to and less than 0.5, the maximum sensitivity can be obtained.

In Fig. 4, a high-speed comparator is used to compare the voltage of the absolute value signal B of the steady-amplitude signal A (the waveforms of the steady-amplitude signal A and the synchronous detection output signal B are shown in Fig. 6a and 6b); the set comparison voltage S_ut is the amplitude of signal A times, that is, at a phase of and the phase is When the comparators each act once, a rising edge and a falling edge of the signal S_t are generated, and the phase difference between them is Using the edge of the signal S_t to trigger ADC sampling can realize quadrature sampling; the specific waveform is shown in Figure 7.

The temperature sensor can be realized by a precision thermistor, and the temperature information is converted into a voltage signal, which is sampled by the high-speed sampling processor 8 to obtain the temperature data S3.

The high-speed sampling processor performs quadrature sampling on the excitation signal S1 and the output signal S2 of the AC bridge according to the quadrature sampling trigger signal.

The eddy current displacement sensor provided in the above embodiments realizes the method for realizing large-scale, high-precision and high-dynamic-response eddy current, including:

The excitation signal S1 and the output signal S2 of the AC bridge are orthogonally sampled by a dual-channel sampling method, and the loss resistance of the resonant circuit is calculated according to the dual-channel sampling data S1 and S2;

Calculate the coil displacement according to the circuit loss resistance;

According to the temperature S3, the displacement temperature drift after temperature compensation is calculated.

The calculation of the loss resistance of the above resonant circuit includes:

Sample series:

S1x (S ₁₀ S ₁₁ S ₁₂ S ₁₃ ......) is the sampling signal of S1;

S2x(S ₂₀ S ₂₁ S ₂₂ S ₂₃ ......) is the sampling signal of S2;

According to the sampling series, the excitation signal (S1), the bridge output signal (S2) can be expressed as complex numbers:

$\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\frac{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}\sqrt{<span\; class="notranslate">\; (</span>{{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}}{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&angle;</span>\mathrm{<span\; class="notranslate">\; arctan</span>}<span\; class="notranslate">\; (</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\frac{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\frac{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}\sqrt{<span\; class="notranslate">\; (</span>{{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}}{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&angle;</span>\mathrm{<span\; class="notranslate">\; arctan</span>}<span\; class="notranslate">\; (</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\frac{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>$

Where n is the number of samples and is an even number;

The complex impedance of the resonant circuit is:

Take the real part of the complex impedance of the resonant circuit: R=Re(Rx)

as probe loss resistance;

The sampling number n is adjustable in the program, and the dynamic response of the sensor can be changed by adjusting the sampling number in a measurement process. The smaller the sampling number, the higher the dynamic response.

Capacitor (C1) in Figure 1 is only used for blocking DC, and the impedance can be ignored.

The complex impedance of the resonant circuit is:

Take the real part of the complex impedance of the resonant circuit: R = Re (Rx) as the probe loss resistance.

The functional relationship between the loss resistance of the probe and the displacement of the sensor is obtained experimentally, and expressed by a polynomial function; it can be implemented in the following manner.

First, use a precision displacement platform to change the displacement D _O between the sensor and the metal surface to be measured, and record the loss resistance R at the same time; obtain a two-dimensional array:

RD={(R ₀ ,D ₀ ),(R ₁ ,D ₁ ),(R ₂ ,D ₂ ),...};

Then, according to the array, with R as the independent variable and D _X as the dependent variable, polynomial fitting is performed to obtain: D _X = f _dr (R).

According to D _X =f _dr (R), the calculated loss resistance R is substituted into the polynomial "f _dr (R)" in the program to obtain the displacement D _X .

The D _X obtained at this time is affected by temperature; use the following method to realize temperature compensation for the displacement D _X. The main idea is to use the experimental method to obtain the temperature characteristics of the sensor and fit it into a polynomial function. Finally, during the sensor measurement process, according to the fitted function, the temperature drift of the displacement D _X is compensated to obtain the output value D.

First, the temperature drift data of 10 displacements are obtained within the range of the sensor, and each displacement records 10 displacement data at different temperatures. Get 10 two-dimensional arrays:

TD ₀ ={(T ₀ ,D ₀₀ ),(T ₁ ,D ₀₁ ),(T ₂ ,D ₀₂ ),...,(T ₉ ,D ₀₉ )};

TD ₁ ={(T ₀ ,D ₁₀ ),(T ₁ ,D ₁₁ ),(T ₂ ,D ₁₂ ),...,(T ₉ ,D ₁₉ )};

TD ₉ ={(T ₀ ,D ₉₀ ),(T ₁ ,D ₉₁ ),(T ₂ ,D ₉₂ ),...,(T ₉ ,D ₉₉ )};

For two-dimensional arrays, TD ₀ , TD ₁ ... TD ₉ respectively take temperature (T) as the independent variable and displacement (D) as the dependent variable, and use polynomial fitting method to obtain 10 functional relations:

D ₀ = f _dt0 (T); D ₁ = f _dt1 (T); ...; D ₉ = f _dt9 (T);

Then use the temperature sensor (5) to obtain the current temperature value (S3); substitute the 10 functional relationships obtained by fitting in the previous step to obtain a two-digit array:

DD _T ＝{(D ₀ ,D _T0 ),(D ₁ ,D _T1 ),(D ₂ ,D _T2 ),...(D ₉ ,D _T9 )}; according to the two-dimensional array D _T , Taking D _TX as the independent variable and the standard displacement D as the dependent variable, the fitting equation D=f _ddt (D _TX ) is obtained by performing an online piecewise linear fitting.

Finally, substitute D _X into D=f _ddt (D _TX ) to obtain the displacement D after temperature compensation.

Although the embodiments disclosed in the present utility model are as above, the content described is only an embodiment adopted for the convenience of understanding the present utility model, and is not intended to limit the present utility model. Anyone skilled in the technical field to which the utility model belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the utility model, but the patent of the utility model The scope of protection must still be based on the scope defined in the appended claims.

Claims (3)

1. A large-scale, high-precision, high-dynamic-response eddy-current displacement sensor is characterized in that the sensor comprises an AC resonant step-up bridge, an amplitude stabilization circuit, an amplitude compensation and addition circuit, a quadrature sampling trigger signal generation circuit and a high-speed sample processor; the The AC resonant boost bridge consists of a resonator, a resistor (R2) connected in parallel with the resonator, and a capacitor (C1) and a resistor (R1) connected in series with the resonator; the resonator consists of an inductance probe (Lx), two Composed of series capacitors (C2, C3); The amplitude stabilization circuit is composed of a variable gain amplifier (4), a synchronous detection circuit (3), an amplitude averaging circuit (6) and a comparison regulator (7); Amplitude compensation and addition circuit, composed of op amp and resistor; The quadrature sampling trigger signal generating circuit is composed of a high-speed comparator. The comparator is provided with two input ends, one of which is connected to the output end of the synchronous detection circuit (3), and the other end is input with a DC voltage (S_ut). 2. The large-range, high-precision and high-dynamic-response eddy-current displacement sensor as claimed in claim 1 is characterized in that, the resonator included in the AC resonant boost bridge is provided with a tap, and the tap is arranged on the capacitor (C3) both ends. 3. large scale high precision high dynamic response eddy current displacement sensor as claimed in claim 1, is characterized in that, the input end of described comparative regulator is respectively the output signal (C) and reference voltage (S_ua) of amplitude averaging circuit .