A kind of frequency-modulation variable area eddy current displacement sensor
Technical field
The utility model relates to a kind of displacement transducer, specifically is a kind of frequency-modulation variable area eddy current displacement sensor.
Background technology
Eddy current displacement sensor can be divided into clearance-changed type, changed area, solenoid type and low frequency transmission-type 4 classes by structure.The changed area sensor is made of the flattened rectangular coil, and it utilizes the variation of the caused eddy current effect power of variation of relative area coverage between measured conductor and the sensor flattened rectangular coil to come Displacement Measurement.
What eddy current displacement sensor adopted is the induced electricity vortex principle.When the pancake coil that has high-frequency current when the tested metal, high-frequency current on the coil is being detected generation induced electricity eddy current on the metal surface, this induced electricity eddy current influences the inductance value of pancake coil again conversely, the size of pancake coil inductance value just with the physical dimension that overlaps area, tested metal of pancake coil and tested metal surface, pancake coil to parameter correlations such as the geometric configuration of the vertical range of tested metal covering, pancake coil, physical dimension, the number of turns, conductivity, magnetic permeabilities.After fixing back seven parameters except that overlapping area, the coincidence area of pancake coil and tested metal parallel surfaces has just produced the single-valued function relation with the inductance value of coil, because the coincidence area of pancake coil and tested metal parallel surfaces is relevant with the big or small monodrome of the opposing parallel displacement between them, thereby the inductance value of shift value and coil has produced the single-valued function relation.Coils from parallel connection of coils definite value electric capacity is connected in the oscillatory circuit, has just set up the parallel displacement of pancake coil and tested metal surface and the single-valued function relation of oscillation frequency, determine displacement with regard to the available oscillation frequency that records.Coil, oscillatory circuit and tested sheet metal have just been formed frequency-modulation variable area type eddy current displacement sensor.Frequency-modulation variable area type eddy current displacement sensor is so that it is simple in structure, highly sensitive, linear measurement range is big, antijamming capability is strong, the advantage such as untouchable of low cost of manufacture and measurement has obtained widespread use.
The shortcoming of eddy current displacement sensor is that the inductive coil temperature influence is bigger, has reduced measuring accuracy, has limited its usable range, need do temperature compensation; The changed area eddy current displacement sensor also has pancake coil to be difficult to keep problem accurately constant, that influence measuring accuracy to the vertical range (degree of approach) of tested sheet metal in the two parallel displacement, need do degree of approach compensation.
Present temperature compensation measure mainly contains: 1. increase thermal sensing element, carry out temperature compensation by the variation of serial connection thermal sensing element sense temperature in bridge circuit.This requires the temperature varying coefficient of the temperature varying coefficient of thermal sensing element and inductive coil proportional, and the variation in the two temperature field of living in should be identical, brings very big inconvenience for processing of circuit and parts selection; 2. increase the differential compensation coil, realization is differential with inductive coil, and is simple in structure effective; 3. use noninductive compensating coil to be connected to bridge circuit, fixed tentering sine wave drive frequently, magnitude demodulator, differential compensation, circuit complexity.4. adopt many litzendraht wires to reduce coil resistance, reduce the influence of temperature, but increased the difficulty of coil winding coil impedance.These several measures have obtained application on the fixed type of amplitude modulation frequently eddy current displacement sensor, effect is better, but also have the complicated shortcoming of hardware.
The scheme that frequency-modulation variable area type eddy current displacement sensor is commonly used at present is that differential winding-double oscillator-frequency/voltage conversion demodulation-differential amplification-hardware logarithm processing-A/D conversion-single-chip microcomputer is handled output, and hardware is comparatively complicated, and volume is big, cost is higher.
Frequency-modulation variable area type eddy current displacement sensor is simple in structure with it, Direct Digitalization, the range of linearity are wide, highly sensitive, cost is low is good at, if the differential compensation coil can be set and use software direct-reading frequency, carry out temperature compensation with the method for computing again, carry out degree of approach compensation with degree of approach compensating coil, just can constitute frequency-modulation variable area type eddy current displacement sensor simple in structure, that volume is little, performance is strong.
The utility model content
In order to overcome the shortcoming that above-mentioned prior art exists, the purpose of this utility model is to provide a kind of frequency-modulation variable area eddy current displacement sensor, it carries out the compensation of the temperature and the degree of approach simultaneously and carries out gamma correction with software, and simple in structure, volume is little, performance is strong.
The technical solution of the utility model is: a kind of frequency-modulation variable area eddy current displacement sensor, the oscillating circuit board that comprises the oscillator coil of flat rectangular, is fixed together with the non-moving reference member of displacement measurement, with the relatively-stationary current vortex Target Board of tested moving target position; Comprise also that an oscillation frequency is read, computing and gamma correction plate; Described oscillating circuit board is provided with the identical modulating oscillation circuit of two cover circuit components, and every cover modulating oscillation circuit comprises two oscillator coils; Two ends on the tested sense of displacement of oscillating circuit board, every end cementation with cover two of modulating oscillation circuit series connection oscillator coil and position parallel relatively; The flat horizontal surface of each oscillator coil is parallel with the plate face of current vortex Target Board, and the vertical junction recency between the plate face of the flat horizontal surface of two oscillator coils of same cover modulating oscillation circuit and current vortex Target Board compensates mutually; The current vortex Target Board the length on the tested sense of displacement be oscillator coil on tested sense of displacement the outer length of side and two the cover oscillator coils two near between the limit apart from sum; The described oscillation frequency of two cover modulating oscillation circuits output terminations is read, computing, gamma correction plate.
As further technical scheme of the present utility model:
In this frequency-modulation variable area eddy current displacement sensor, also comprise the oscillating capacitance of high stable, integrated two reversers in described every cover modulating oscillation circuit; Described integrated two reversers comprise first reverser and two reversers of second reverser; After the input end of the output terminal of first reverser and second reverser joins, connect the input end of a resistance again to first reverser, input end by first reverser picks out a coupling capacitance, connect a repeating resistance of series connection, the output terminal that a coupling capacitance is coupled to second reverser again, by output termination one source resistance of second reverser to positive power source terminal, by positive supply termination one decoupling capacitance to ground; End of the same name with two oscillator coils in the cover modulating oscillation circuit is connected in series mutually, the contact that is connected to coupling capacitance that the input end by first reverser picks out and repeating resistance behind the oscillating capacitance in parallel again is to the ground, the size of decision oscillation frequency is regulated oscillating capacitance, the scalable oscillation frequency; Output terminal output vibration square wave by second reverser.
In this frequency-modulation variable area eddy current displacement sensor, described oscillating circuit board is an one flat plate; Two oscillator coils with the cover modulating oscillation circuit are separately fixed on the pros and cons of oscillating circuit board with end two oscillator coil location overlaps; The current vortex Target Board is the U-shaped stiff sheet that a usefulness high conductivity low magnetic permeability material is made, and comprises two limit panels that be arranged in parallel and a crestal surface plate that is vertically connected between the panel of both sides, and limit panel, crestal surface plate are rectangle; Oscillating circuit board is set in parallel between the both sides panel of current vortex Target Board.
Another kind of technical scheme: in this frequency-modulation variable area eddy current displacement sensor, described oscillating circuit board comprises left oscillating circuit board, right oscillating circuit board; With the corresponding respectively same end that is fixed on left oscillating circuit board, right oscillating circuit board of two oscillator coils of cover modulating oscillation circuit, and two oscillator coil positions are parallel relatively; The current vortex Target Board is the rectangular flat that a usefulness high conductivity low magnetic permeability material is made, parallel placing between left oscillating circuit board, the right oscillating circuit board.
In this frequency-modulation variable area eddy current displacement sensor, the one-chip computer that described oscillation frequency is read, computing, gamma correction plate comprise two analog switches, two frequency dividers, store the relevant treatment program; The input end of described two analog switches is corresponding one by one continuous with the output terminal of two cover modulating oscillation circuits respectively; The input end of the output terminal of two analog switches and two frequency dividers is corresponding one by one to link to each other, and two frequency dividers are exported oscillation frequency with modulating oscillation circuit and reduced the PO mouth that is delivered to one-chip computer after the certain multiple by its delivery outlet; The Push And Release of described two analog switches is by the control end control of one-chip computer.
The beneficial effects of the utility model are:
1. circuit component is few, and layout is simple, and cost is low;
2. employing frequency readings, software processing method is realized the frequency modulation digitizing, has saved hardware such as the demodulation of common scheme, differential amplification, A/D conversion, hardware linearization, antijamming capability is strong when transmission;
3. use the design simply and especially of four flat rectangular sensing oscillator coils and current vortex Target Board relative position, finished the compensation of the temperature and the degree of approach;
4. the polynomial expression on the application one-chip computer fits gamma correction, makes the range of linearity of displacement transducer wideer, and precision is higher.
Description of drawings
Fig. 1 is the modulating oscillation circuit figure in the utility model;
Fig. 2 is the structural representation of embodiment one,
Fig. 3 looks sectional view for the right side of embodiment one;
Fig. 4 is the deployed configuration synoptic diagram of the oscillating circuit board of embodiment two,
Fig. 5 looks sectional view for the right side of embodiment two;
Fig. 6 is the structural representation of the current vortex Target Board of embodiment two,
Fig. 7 is for oscillation frequency is read, the block scheme of computing, gamma correction plate;
Fig. 8 is for oscillation frequency is read, the hardware configuration of computing, gamma correction plate.
Among the figure: 1 oscillating circuit board, 2 current vortex Target Boards, 21 left side panels, 22 the right panels, 23 crestal surface plates, the nonmetal web member of 4U shape, 5 left oscillating circuit boards, 6 right oscillating circuit boards, 7 current vortex Target Boards, 8 nonmetal web members, the series line between 9 oscillator coil L1 and L2, the series line between 10 oscillator coil L3 and L4.
Embodiment
Two embodiment: embodiment one of the present utility model are the oscillating circuit board that adopts a plane, the current vortex Target Board of a U-shaped, shown in Fig. 2,3; Embodiment two adopts two oscillating circuit boards, and the current vortex Target Board on a plane is shown in Fig. 4,5.Two embodiment only are that oscillating circuit board is different with the version of current vortex Target Board, use identical hardware circuit and software.
Consulting drawings and Examples below is described further the utility model.
Figure 1 shows that the employed two cover modulating oscillation circuits of the utility model, it is made up of two identical cover modulating oscillation circuits of element.Every cover modulating oscillation circuit comprises that (left side cover is U1 to integrated two reversers, right cover is U2, each integrated two reverser comprises first reverser and two reversers of second reverser, under the help of coupling element, produce positive feedback), (left side cover is L1, L2 for the oscillator coil of the flat rectangular of two series connection, right side cover is L3, L4) a NPO oscillating capacitance in parallel (left side is overlapped and is C1, and right cover is C21) and other connection coupling element.(L1+L2) //C1 formation left side cover shunt inductance electric capacity, (L3+L4) //the right shunt inductance electric capacity that overlaps of C21 formation, the decision oscillation frequency.
The structure of left side cover modulating oscillation circuit is as follows: after the input end 2A of the output terminal 1Y of first reverser and second reverser joins among the integrated two reverser U1, meet the input end 1A of a resistance R 2 to first reversers again, input end 1A by first reverser picks out a coupling capacitance C2, meet a repeating resistance R1 of series connection, the output terminal 2Y that a coupling capacitance C3 is coupled to second reverser again, output terminal 2Y by second reverser meets a source resistance R3 to positive power source terminal V, meets a decoupling capacitance C4 to ground D by positive power source terminal V.Left side cover shunt inductance electric capacity (L1+L2) // contact that C1 is connected to coupling capacitance C2 that the input end 1A by first reverser picks out and repeating resistance R3 determines the size of oscillation frequency to the ground D.Regulate the relative size of R2, C2, R1, C3, control modulating oscillation circuit starting condition for oscillation, left side cover shunt inductance electric capacity (L1+L2) //the oscillator signal amplitude and the stability at C1 two ends.Regulate the size of NPO oscillating capacitance C1, the height of control oscillation frequency.At last, the output terminal 2Y (being the O1 end) by second reverser exports the vibration square wave.
Right cover modulating oscillation circuit comprises integrated two reverser U2, resistance R 22, coupling capacitance C22, repeating resistance R21, coupling capacitance C23, source resistance R23, decoupling capacitance C24, oscillator coil L3, L4, NPO oscillating capacitance C21.The input end of first reverser in the integrated two reverser U2 is 3A, and output terminal is 3Y, and the input end of second reverser is 4A, and output terminal is 4Y.The structure of right cover modulating oscillation circuit and principle are identical with left side cover modulating oscillation circuit, repeat no more.
Fig. 2,3 is depicted as embodiment one: oscillating circuit board 1 is made by the low thermal coefficient of expansion material, and is affixed with tested displacement object of reference.
Current vortex Target Board 2 comprises left side panel 21, the right panel 22 and crestal surface plate 23 that is vertically connected between the panel of both sides that be arranged in parallel, forms U-shaped.Left side panel, the right panel, crestal surface plate are rectangle.Oscillating circuit board 1 is set in parallel between the left side panel 21, the right panel 22 of current vortex Target Board.Left side panel 21, the right panel 22 and crestal surface plate 23 are made by the material that thickness is not thinner than high conductivity low magnetic permeabilities such as the smooth smooth copper coin of 0.5mm or aluminium sheet.Oscillator coil L1, L2 location overlap ground cement on the tow sides of upper end of oscillating circuit board 1 with the low thermal coefficient of expansion cementing agent respectively.Oscillator coil L3, L4 location overlap ground cement on the tow sides of lower end of oscillating circuit board 1 with the low thermal coefficient of expansion cementing agent respectively.The vertical range of the plate face of the flat horizontal surface of each oscillator coil and current vortex Target Board (being the degree of approach) is about 1.8mm.Because left side panel 21, the right panel 22 of current vortex Target Board are one, oscillator coil L1, L3 and left side panel 21 degrees of approach increase or when dwindling, oscillator coil L2, L4 and the right panel 22 degrees of approach are just done dwindling of same amount or are increased, and promptly the vertical junction recency between the plate face of the flat horizontal surface of two oscillator coils of cover modulating oscillation circuit and current vortex Target Board compensates mutually together.This structure remains unchanged total degree of approach (two inductance degree of approach sums) of oscillator coil L1, L2 and L3, L4, and this has obtained compensation with regard to making the degree of approach to the influence of oscillation frequency.
Distance L between the both sides that oscillator coil L1 and L3 are close, between the both sides that are close of L2 and L4 can be made as about 9mm, can reduce between L1 and the L3 like this, the mutual electromagnetic between L2 and the L4 disturbs.
The line direction of two cover rectangle oscillator coils fixes on the tested sense of displacement on the direction on the crestal surface plate 23 long limits of current vortex Target Board 2 and the oscillating circuit board 1.The left side panel 21 of current vortex Target Board 2, the right panel 22 are the width A of oscillator coil on the tested sense of displacement and the distance L sum between the nearest both sides of two cover coils in the length on the tested sense of displacement.On the direction of vertical tested displacement, the left side face of current vortex Target Board 2, the width M of the right panel are a bit larger tham 1.5 times of width on this direction of each oscillator coil.
The left side panel of current vortex Target Board, the right panel and tested displacement object are fixedly connected the position relative fixed by the nonmetal web member 4 of a U-shaped during use.When being subjected to displacement, two cover oscillator coil L1, L2 are just in time opposite by the variation of current vortex Target Board 2 area coverages with L3, L4, thereby the variation of two cover modulating oscillation circuit oscillation frequency is also just in time opposite, and the slope (sensitivity) that two cover modulating oscillation circuit oscillation frequency rate variances change doubles.Because temperature is in the same way to the influence of two cover modulating oscillation circuit oscillation frequency, so the temperature drift of two cover modulating oscillation circuits disappears concerning difference on the frequency substantially mutually, has realized temperature compensation, has strengthened the temperature stability of difference on the frequency.
Fig. 4,5 is depicted as embodiment two: its oscillating circuit board comprises left oscillating circuit board 5, right oscillating circuit board 6.Left side oscillating circuit board 5, right oscillating circuit board 6 and tested displacement object of reference are affixed.Oscillator coil L1, L3 cement in the upper and lower end of left oscillating circuit board 5 respectively, and oscillator coil L2, L4 cement in the upper and lower end of right oscillating circuit board 6 respectively, all use low thermal coefficient of expansion cementing agent cementation.L1, L2 position are parallel relatively, and L3, L4 position are parallel relatively.The end of the same name of oscillator coil L1, L2 is connected in series; The end of the same name of oscillator coil L3, L4 is connected in series; 9 is series line between oscillator coil L1 and L2 among Fig. 4,5, and 10 is the series line between oscillator coil L3 and L4.
On tested sense of displacement, the distance that L3 and L1 join between the near side (ns), L4 and L2 join between the near side (ns) is about 9mm, can reduce between L1 and the L3 like this, the mutual electromagnetic between L2 and the L4 disturbs.
This current vortex Target Board 7 is a rectangular flat, makes with the material of high conductivity low magnetic permeabilities such as copper or aluminium, parallel placing between left oscillating circuit board 5, the right oscillating circuit board 6.Current vortex Target Board 7 the length on the tested sense of displacement be oscillator coil on the tested sense of displacement width A and two the cover coils near the distance L sum between both sides.On the direction of vertical tested displacement, the width M of current vortex Target Board 7 is 1.5 times of width on this direction of oscillator coil.
Current vortex Target Board 7 is connected the position relative fixed with tested displacement object by nonmetal web member 8.Vertical range is about 1.8mm between the plate face of the flat horizontal surface of oscillator coil L1, L2, L3, L4 and current vortex Target Board 7.
Because left oscillating circuit board 5, right oscillating circuit board 6 fronts are relatively, the position relative fixed, sandwich plane Target Board 7, this structure changes in the opposite direction the vertical range (being the degree of approach) of the relative current vortex Target Board with L4 of oscillator coil L1 and L2, L3 7 plate faces, make total degree of approach of oscillator coil L1, L2 and L3, the relative current vortex Target Board 7 plate faces of L4 constant, this has obtained compensation with regard to making the degree of approach to the influence of oscillation frequency.
Identical with embodiment one, current vortex Target Board 7 and tested displacement object's position relative fixed, two cover oscillator coil L1, L2 are just in time opposite by the variation of current vortex Target Board 7 area coverages with L3, L4, thereby, the variation of two cover modulating oscillation circuit oscillation frequency is also just in time opposite, and the slope (sensitivity) that two cover modulating oscillation circuit oscillation frequency rate variances change doubles.Because temperature is in the same way to the influence of two cover modulating oscillation circuit oscillation frequency, so the temperature drift of two cover modulating oscillation circuits disappears concerning difference on the frequency substantially mutually, has realized temperature compensation, has strengthened the temperature stability of difference on the frequency.
The oscillation frequency that Figure 6 shows that this utility model is read, computing, gamma correction plate hardware block diagram, comprises analog switch, frequency divider, one-chip computer.
Figure 7 shows that oscillation frequency is read, computing, hardware embodiment of gamma correction plate.Comprise integrated analog switch CD4052, frequency divider 74LS393, one-chip computer AT89S52.
The input end of two analog switches of integrated analog switch CD4052 is corresponding one by one continuous with the output terminal of two cover modulating oscillation circuits respectively.The output terminal of two analog switches is corresponding one by one continuous with the input end CLK of two frequency dividers.Two frequency dividers reduce certain multiple with the oscillation frequency of each self-corresponding modulating oscillation circuit output, are outputed to the P0 mouth (P0.0, P0.1, P0.2, P0.3, P0.4, P0.5, P0.6, P0.7) of one-chip computer then respectively by delivery outlet Q1, Q2, Q3, Q4.When cutting off analog switch 3 after the A of the one-chip computer control end control conducting unit interval, read and record count information by P0 mouth and T0, T1 counter, one-chip computer draws actual frequency as calculated, calculate again the difference on the frequency of two cover frequency hopping oscillatory circuits; The polynomial expression of storing in the program according to difference on the frequency and one-chip computer fits the coefficient in the formula, draws the measured position shift.At last, when host computer required to send tested displacement, one-chip computer was by serial port TXD, and RXD is transplanted on host computer with measured position.Wherein, described polynomial expression fit coefficient in the formula by the MATLAB in the computing machine or ORIGIN software program to many to measured displacements---difference on the frequency is done polynomial expression and is fitted and draw, and is solidificated in the one-chip computer then.The Push And Release of two analog switches is by the control end A control end control of one-chip computer.
The utility model is not limited only to the foregoing description.