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

Abstract

The utility model discloses a high dynamic response eddy current displacement sensor of wide range high accuracy, including exchanging resonance step -up electric bridge, fixed ampllitude circuit, range compensation and add circuit, quadrature sampling triggering signal generating circuit and high -speed sampling treater, interchange resonance step -up electric bridge reaches by the syntonizer, with the parallelly connected resistance (R2) of syntonizer and constitutes with the electric capacity (C1) and the resistance (R1) of syntonizer series connection, the syntonizer comprises inductance probe (Lx), two series capacitance (C2, C3), the fixed ampllitude circuit comprises variable gain amplifier (4), synchronous detection circuit (3), range averaging circuit (6) and comparison regulator (7), range compensation and add circuit are put and resistors by fortune, quadrature sampling triggering signal generating circuit comprises fast comparator, and this comparator is provided with two inputs, wherein the one end connection on the output of synchronous detection circuit (3), other end input direct -current voltage (S_ut).

Description

A kind of large range high precision high dynamic response eddy current displacement sensor

Technical field

This utility model relates to eddy current displacement sensor, particularly relates to the electricity of a kind of large range high precision high dynamic response Eddy displacement sensor.

Background technology

The ultimate principle of such sensor is that the coil launching alternating electromagnetic field there will be eddy current effect, line when metal Circle is the nearest to metal covering distance, is lost the biggest.In the case of ceteris paribus, sensing can be measured by measuring loss Device and the distance of metal covering.

At present, the range of linearity of eddy current displacement sensor only has the half of probe diameter；In measuring range, inductance is visited The excursion of head output signal is little, and sensitivity is low；Using the absolute value detection of diode-type, anti-interference is low；And it is internal The shortcomings such as integrated substantial amounts of analog device, causes temperature to waft seriously, system complex.

Summary of the invention

For solving above-mentioned technical problem, the purpose of this utility model is to provide a kind of large range high precision high dynamic response Eddy current displacement sensor, sensor is high reliability, the eddy current displacement sensor of Low Drift Temperature；This sensor is widely used in position Shifting, vibration measurement, it is also applied for production line condition monitoring.

The purpose of this utility model is realized by following technical scheme:

A kind of large range high precision high dynamic response eddy current displacement sensor, including: exchange resonance step-up electric bridge, fixed ampllitude Circuit, Amplitude Compensation trigger signal generating circuit and high-speed sampling processor with add circuit, quadrature sampling；Described

Exchange resonance step-up electric bridge, the resistance (R2) in parallel with resonator by resonator and the electric capacity connected with resonator (C1) form with resistance (R1)；Described resonator is made up of inductance probe (Lx), two series capacitances (C2, C3)；

Fixed amplitude circuit, by variable gain amplifier (4), synchro detection circuit (3), amplitude average circuit (6) with compare tune Joint device (7) composition；

Amplitude Compensation and add circuit, be made up of with resistance amplifier；

Quadrature sampling triggers signal generating circuit, is made up of high-speed comparator, and this comparator is provided with two inputs, its Middle one end is connected on the outfan of synchro detection circuit (3), other end input direct voltage (S_ut).

Compared with prior art, one or more embodiment of the present utility model can have the advantage that

Use Amplitude Compensation technology, the output area of sensor can be increased, improve sensitivity；

Use high-speed comparator, the synchronous detection signal B of fixed ampllitude is carried out Amplitude Ratio relatively, thus produce quadrature sampling and trigger Signal；This method simple in construction, can produce the quadrature sampling that phase contrast is 90 degree reliably and trigger signal (S_t)；

Use measuring probe coil and two capacitances in series, and from an electric capacity two ends input stimulus；In identical excitation Under voltage conditions, compare from coil two ends input signal, the driving voltage at inductance coil two ends can be significantly improved, increase Measurement scope；

Use high-speed comparator and high-speed analog switch composition lock detector, compare with the absolute value electricity of diode composition Road, has that speed is fast, precision is high, the advantage of good stability；

Using phase contrast is the quadrature sampling method of 90 degree, reduces sampling rate, and can be easy try to achieve probe The impedance of inductance coil；The method simultaneously using Digital Signal Processing carries out signal processing good stability, knot than with analog circuit Structure is simple, reconstruct convenient advantage.

When sensor does one-shot measurement, number of samples n can adjust, and adjusts number of samples and can change the dynamic sound of system Should；When measuring, number of samples n is the least every time, and dynamic response is the highest, and owing to gathering pumping signal S1 and the output letter of electric bridge Number S2 is as measuring the foundation of displacement, and the dynamic response of sensor is not only restricted to the dynamic response of fixed amplitude circuit；System dynamic Respond only relevant with number of samples n with sample frequency.

Polynomial fitting is used to correct the warm method waftd of measuring of sensor, than the general look-up table speed used more Hurry up, memory capacity is less, improves the frequency response performance of sensor.

Accompanying drawing explanation

Fig. 1 is large range high precision high dynamic response eddy current displacement sensor structure chart；

Fig. 2 is fixed amplitude circuit；

Fig. 3 is Amplitude Compensation and add circuit；

Fig. 4 is that quadrature sampling triggers signal generating circuit；

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

Fig. 6 a and 6b is the waveform of fixed ampllitude signal (A) and synchronous detection output signal (B)；

Fig. 7 is the waveform that quadrature sampling triggers signal (S_t) and synchronous detection output signal (B).

Detailed description of the invention

For making the purpose of this utility model, technical scheme and advantage clearer, below in conjunction with embodiment and accompanying drawing pair This utility model embodiment is described in further detail.

As it is shown in figure 1, be large range high precision high dynamic response eddy current displacement sensor, described sensor includes exchange Resonance step-up electric bridge, fixed amplitude circuit, Amplitude Compensation trigger at signal generating circuit and high-speed sampling with add circuit, quadrature sampling Reason device；Described

Exchange resonance step-up electric bridge, the resistance (R2) in parallel with resonator by resonator and the electric capacity connected with resonator (C1) form with resistance (R1)；Described resonator is made up of inductance probe (Lx), two series capacitances (C2, C3)；

Fixed amplitude circuit, by variable gain amplifier (4), synchro detection circuit (3), amplitude average circuit (6) with compare tune Joint device (7) composition；

Amplitude Compensation and add circuit, be made up of with resistance amplifier；

Quadrature sampling triggers signal generating circuit, is made up of high-speed comparator, and this comparator is provided with two inputs, its Middle one end is connected on the outfan of synchro detection circuit (3), other end input direct voltage (S_ut).

Being provided with tap in the resonator that above-mentioned exchange resonance step-up electric bridge comprises, this tap setting is the two of electric capacity (C3) End.

The above-mentioned input comparing actuator is output signal (C) and the reference voltage (S_ of amplitude average circuit respectively ua)。

The present embodiment uses Amplitude Compensation technology can increase the output area of sensor, improves sensitivity.Its reason is such as Under: assume inductance probe measure displacement minimum and maximum between, the codomain of its loss resistance Rx is { R_x|R_min≤R_x≤R_max,

OrderThen K_rxCodomain be

May be assumed that

$K_{rx\_\min }=\frac{R_{\min }}{R_{\min }+R1},K_{rx\_\max }=\frac{R_{max}}{R_{max}+R1},$

Then K_rxCodomain be { K_rx|K_{rx_min}≤K_rx≤K_{rx_max}}；

When assuming electric bridge fixed ampllitude excitation (S1=A), output (S2) scope of sensor is:

D_{ran_1}=A* (K_{rx_max}-K_{rx_min}),

When electric bridge band Amplitude Compensation, compensation way is: S1=K*S2+A, and its output (S2) scope is:

$D_{ran\_2}=\frac{A*(K_{rx\_\max }-K_{rx\_\min })}{(1-K*K_{rx\_\max })*(1-K*K_{rx\_\min })},$

Work as K*K_rxDuring ＜ 1,

$\frac{1}{(1-K*K_{rx\_max})*(1-K*K_{rx\_\min })}>1,$

So D_{ran_2}＞ D_{ran_1},

Amplitude Compensation technology can improve the output area of sensor, also improves sensitivity simultaneously.

Above-mentioned inductance Lx is the coil of current vortex sensor probe, and the electromagnetic field of this coil transmissions high frequency, when coil is close During metal covering, produce eddy current effect, eddy-current loss occurs；And distance is the nearest, is lost the biggest.Resistance R1 is proportion divider electricity Resistance；Resistance R2 is decay build-out resistor, by adjusting R2 resistance, the attenuation ratio of adjustable electric bridge；Electric capacity C2, C3 are resonance electricity Hold；Electric capacity C1 is partiting dc capacitor.The pumping signal of electric bridge is S1, output signal is S2, and this electric bridge and outside amplifier Forming controlled self-excited circuit, the frequency of self-excitation is determined by the inductance value of the Lx that pops one's head in, the size of electric capacity C2, C3.Amplitude Compensation with In add circuit: input signal is made up of resonator output signal S2 and fixed ampllitude signal A, outside controlled self-excited circuit determines The magnitude relationship of bridge signal is: S1=K*S2+A, and wherein " K " is penalty coefficient, and A is fixed ampllitude signal, and this signal is defeated with electric bridge Go out signal S2 with frequency homophase.From the point of view of AC bridge (C1, C2, C3, R1, R2, Lx) self, if voltage divider system is K_rx, permissible Obtain S2=K_rx*S1；The size of S2 is together decided on by the dividing potential drop relation of outside amplifying circuit and AC bridge self.Use width The method that degree compensates can expand range and the sensitivity of eddy current displacement sensor；But overall gain (the K*K of loop_rx) to control In the range of less than 1, otherwise loop is by out of hand.Meanwhile, by changing the given of fixed amplitude circuit, fixed ampllitude superposition can be realized The amendment of the amplitude of signal, finally can change pumping signal S1 on AC bridge and output signal S2.

The input signal of above-mentioned variable gain amplifier is from output signal S2 of electric bridge, and output signal A is fixed ampllitude signal, This fixed ampllitude signal is average 6 by synchronous detection 3, amplitude, compare actuator 7 forms closed loop control network and realizes.Detailed process is: The signal that synchronous detection is equivalent to needing fixed ampllitude takes absolute value；Then the signal B taken absolute value is carried out amplitude average, quite Amplitude information in fixed ampllitude signal is converted into DC voltage C；This voltage C compares with given DC voltage S_ua, and Do negative-feedback regu-lation so that the meansigma methods of the absolute value of output signal A is consistently equal to given DC voltage S_ua, reaches fixed ampllitude Purpose.

In fig. 2, high-speed comparator U7 triggers at the zero crossing of signal, forms a square-wave signal.This square-wave signal control High-speed analog switch U5 processed；When input signal A is less than zero, the inversion signal of analog switch U5 output signal A；This inversion signal The inverting amplifier being made up of amplifier U4A, resistance R11, R15 realizes.It is reverse signal due to export when signal is less than zero, During more than zero, output is positive phase signals, has been achieved in that the computing taking absolute value input signal A.

In figure 3, amplifier U2A and resistance R3, R4, R9 and R12 constitute Amplitude Compensation and add circuit；Effect is to electricity Bridge output signal S2 compensates, and plus fixing pumping signal A.The output of this circuit 1 is believed as the excitation of AC bridge Number S1, one of them example is, as R3=5K, R4=10K, R9=5K, R12=10K, can realize the signal of S1=2*S2+A Output, is equivalent to amplify output signal S2 the twice then superposition fixed ampllitude signal A pumping signal as electric bridge；Now electric bridge Maximum dividing potential drop COEFFICIENT K_rxClose to and during less than 0.5, maximum sensitivity can be obtained.

In the diagram, use high-speed comparator that absolute value signal B of fixed ampllitude signal A carries out voltage ratio relatively (fixed ampllitude signal A With the waveform of synchronous detection output signal B as shown in figure 6 a and 6b)；The comparison voltage S_ut set is as signal A amplitude Times, in phase place it is i.e.With phase place it isTime each action of comparator once, produce signal S_t a rising edge and once under Fall edge, between phase contrast beSample with the edging trigger ADC of this signal S_t, quadrature sampling can be realized；Concrete waveform exists In Fig. 7.

Temperature sensor can realize with accurate critesistor, temperature information is converted to voltage signal, at high-speed sampling Reason device 8 sampling obtains temperature data S3.

High-speed sampling processor triggers signal according to quadrature sampling, pumping signal S1 and output signal S2 to AC bridge Carry out quadrature sampling.

The eddy current displacement sensor that above-described embodiment provides realizes the side of large range high precision high dynamic response current vortex Method includes:

By the two-way method of sampling, pumping signal S1 and output signal S2 of AC bridge are carried out quadrature sampling, according to double Road sampled data S1, S2 calculate resonant circuit losses resistance；

According to circuit loss resistance calculations coil displacements；

According to temperature S3, calculate the displacement temperature after temperature-compensating and waft.

The calculating of above-mentioned resonant circuit losses resistance includes:

Sample series:

S1x(S₁₀ S₁₁ S₁₂ S₁₃...) it is the sampled signal of S1；

S2x(S₂₀ S₂₁ S₂₂ S₂₃...) it is the sampled signal of S2；

According to sample series, pumping signal (S1), the available complex representation of bridge output signal (S2) is:

$S1=\frac{\underset{i=0}{\overset{\frac{n}{2}-1}{\Σ}}\sqrt{({S_{1(i*2)}}^2+{S_{1(i*2+1)}}^2)}}{\left(\frac{n}{2}\right)}\∠\arctan \left(\frac{\underset{i=0}{\overset{\frac{n}{2}-1}{\Σ}}\left(\frac{S_{1(i*2)}}{S_{1(i*2+1)}}\right)}{\left(\frac{n}{2}\right)}\right)$

$S2=\frac{\underset{i=0}{\overset{\frac{n}{2}-1}{\Σ}}\sqrt{({S_{2(i*2)}}^2+{S_{2(i*2+1)}}^2)}}{\left(\frac{n}{2}\right)}\∠\arctan \left(\frac{\underset{i=0}{\overset{\frac{n}{2}-1}{\Σ}}\left(\frac{S_{2(i*2)}}{S_{2(i*2+1)}}\right)}{\left(\frac{n}{2}\right)}\right)$

Wherein n is number of samples, and is even number；

Resonance circuit complex impedance is:

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

As probe loss resistance；

Described number of samples n is the most adjustable, can be come by the size of number of samples during adjustment one-shot measurement Changing the dynamic response of sensor, number of samples is the least, and dynamic response is the highest.

In Fig. 1, electric capacity (C1) is only stopping direct current effect, and impedance is negligible.

Resonance circuit complex impedance is:

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

Obtain the functional relationship between probe loss resistance and sensor displacement with laboratory method, and represent with polynomial function Out；Mode under may be used to is carried out.

The displacement D between sensor and tested metal covering is changed first by precision displacement platform_O, recording loss electricity simultaneously Resistance R；Obtain two-dimensional array:

RD={ (R₀,D₀), (R₁,D₁), (R₂,D₂) ...；

Then according to this array, with R as independent variable, D_XFor dependent variable, do fitting of a polynomial and obtain: D_X=f_dr(R)。

According to D_X=f_dr(R) this multinomial " f is substituted into calculated loss resistance R in a program_dr(R) " displacement is obtained Amount D_X。

The D now obtained_XAffected by temperature；By following mode, it is achieved to displacement D_XTemperature-compensating.Mainly Thought is the temperature characterisitic experimentally obtaining sensor, and fits to polynomial function, finally in sensor measurement mistake The function obtained according to matching in journey, compensates displacement D_XTemperature waft, obtain output valve D.

First the temperature obtaining 10 displacements in the range of transducer range is waftd data, 10 different temperatures of each displacement record Under displacement data.Obtain 10 two-dimensional arrays:

TD₀={ (T₀,D₀₀),(T₁,D₀₁),(T₂,D₀₂),......,(T₉,D₀₉)}；

TD₁={ (T₀,D₁₀),(T₁,D₁₁),(T₂,D₁₂),......,(T₉,D₁₉)}；

TD₉={ (T₀,D₉₀),(T₁,D₉₁),(T₂,D₉₂),......,(T₉,D₉₉)}；

To two-dimensional array, TD₀,TD₁......TD₉Respectively with temperature (T) as independent variable, displacement (D) is dependent variable, with many The method of formula matching, obtains 10 functional relations:

D₀=f_dt0(T)；D₁=f_dt1(T)；......；D₉=f_dt9(T)；

Then by temperature sensor (5), current temperature value (S3) is obtained；Substitute into 10 letters that previous step matching obtains Number relation, available two bit array:

DD_T={ (D₀,D_T0),(D₁,D_T1),(D₂,D_T2),......(D₉,D_T9)}；According to two-dimensional array DD_T, with D_TXFor certainly Variable, standard displacement D is that dependent variable does online sectional linear fitting and obtains fit equation D=f_ddt(D_TX)。

Finally D_XSubstitute into D=f_ddt(D_TX), try to achieve the displacement D after temperature-compensating.

Although the embodiment disclosed by this utility model is as above, but described content is only to facilitate understand this practicality Novel and the embodiment that uses, is not limited to this utility model.Skill in any this utility model art Art personnel, on the premise of without departing from the spirit and scope disclosed by this utility model, can be in the formal and details implemented On make any amendment and change, but scope of patent protection of the present utility model, still must be defined with appending claims In the range of standard.

Claims (3)

1. a large range high precision high dynamic response eddy current displacement sensor, it is characterised in that described sensor includes handing over Stream resonance step-up electric bridge, fixed amplitude circuit, Amplitude Compensation trigger signal generating circuit and high-speed sampling with add circuit, quadrature sampling Processor；Described

Exchange resonance step-up electric bridge, the resistance (R2) in parallel with resonator by resonator and the electric capacity (C1) connected with resonator Form with resistance (R1)；Described resonator is made up of inductance probe (Lx), two series capacitances (C2, C3)；

Fixed amplitude circuit, by variable gain amplifier (4), synchro detection circuit (3), amplitude average circuit (6) with compare actuator (7) composition；

Amplitude Compensation and add circuit, be made up of with resistance amplifier；

Quadrature sampling triggers signal generating circuit, is made up of high-speed comparator, and this comparator is provided with two inputs, Qi Zhongyi End is connected on the outfan of synchro detection circuit (3), other end input direct voltage (S_ut).

2. large range high precision high dynamic response eddy current displacement sensor as claimed in claim 1, it is characterised in that described Being provided with tap in the resonator that exchange resonance step-up electric bridge comprises, this tap setting is at the two ends of electric capacity (C3).

3. large range high precision high dynamic response eddy current displacement sensor as claimed in claim 1, it is characterised in that described The relatively input of actuator is output signal (C) and the reference voltage (S_ua) of amplitude average circuit respectively.