CN102706383A - Measurement device and method for differential capacitance type instrument - Google Patents
Measurement device and method for differential capacitance type instrument Download PDFInfo
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- CN102706383A CN102706383A CN2012101816395A CN201210181639A CN102706383A CN 102706383 A CN102706383 A CN 102706383A CN 2012101816395 A CN2012101816395 A CN 2012101816395A CN 201210181639 A CN201210181639 A CN 201210181639A CN 102706383 A CN102706383 A CN 102706383A
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Abstract
The invention relates to a measurement device and method for a differential capacitance type instrument. The device comprises an alternating excitation signal generator, a circuit option switch circuit, an AD (analog-to-digital) converter and a digital signal processor, wherein after the alternating excitation signal generator generates an alternating excitation signal with fixed frequency and fixed amplitude, the alternating excitation signal is applied to two ends of the differential capacitance type instrument through the circuit option switch circuit to realize positive excitation and negative excitation of the differential capacitance type instrument; the output end of an intermediate polar plate of the differential capacitance type instrument is sequentially connected with the AD converter and the digital signal processor, the spectrum data amplitude maximum value acquired by converting the output signal of the intermediate polar plate of the differential capacitance type instrument in the positive excitation and the negative excitation, a variation of a measured physical quantity of the differential capacitance type instrument is acquired according to a certain linear relationship, so that the differential capacitance type instrument can be measured. According to the measurement device, a high accuracy measurement result can be acquired for the differential capacitance type instrument, so that the reliability of a differential resistance type sensor can be improved.
Description
Technical field
The present invention relates to the measurement mechanism and the method for the differential capacitance type instrument in the safety monitoring instrument of health monitoring technical field, particularly Geotechnical Engineering of Geotechnical Engineering.
Background technology
In the safety monitoring field of Geotechnical Engineering; The differential capacitance type instrument is a kind of relatively unique safety monitoring instrument type; Generally be used to realize static liquid level settlement measurement, vertical line displacement measurement, draw the monitoring of physical quantitys such as bracing cable displacement measurement, thermometal mark deformation monitoring, more application is arranged in the safety monitoring engineering.
The differential capacitance type instrument generally (is defined as C by the pairing electric capacity of a pair of parameter symmetry
1And C
2) as the sensitive element of sensor, this has such attribute to pairing electric capacity, when measurand F changes, supposes that variable quantity is △ F, one of them capacitor C
1The appearance value will increase △ C, corresponding with it is another capacitor C
2The appearance value △ C that diminishes, C
1With C
2The changes in capacitance difference be 2 △ C; Because there are linear relationship in △ F and 2 △ C in measurement range; Be that △ F is the single function of 2 △ C, so through measuring the Changing Pattern that 2 △ C just can obtain measurand F, thereby the healthy and safe situation of analysis and judgement Geotechnical Engineering.
Saying that from measuring principle the metering circuit of differential capacitive sensor is very simple, is that AC signal is converted into direct current signal, and uses the direct-flow output signal U of Ohm law through the electric capacity two ends
0With ac-excited signal U
0iBetween the voltage amplitude ratio relation just can realize direct measurement to capacitance △ C.Like
but in fact because the numerical value of △ C very little (in this one magnitude of tens PF); The interference that any link of metering circuit is introduced all can cause measured value inaccurate, like the distributed capacitance of lead, the noise of components and parts etc.Therefore, the high precision of differential capacitance type instrument, high reliability measurement are difficult to realize.
The healthy and safe condition monitoring of Geotechnical Engineering is most important, guarantees that the accuracy of measurement result and reliability are top priorities.Therefore, necessary electric characteristic to the differential capacitance type instrument designs a kind of brand-new measuring system or measuring method, in the hope of obtaining very desirable measurement sensitivity and measuring accuracy.
Summary of the invention
The influence of disturbing factor the present invention is directed to existing differential capacitance type instrument owing to can't obtain the problem of high precision and high reliability measurement result; A kind of measurement mechanism of novel differential capacitance type instrument is provided; This device can overcome the influence of various interference to the measurement result of differential capacitor instrument effectively through the FFT technology, guarantees that the differential capacitance type instrument obtains the high-acruracy survey result.
The invention still further relates to a kind of measuring method of differential capacitance type instrument.
Technical scheme of the present invention is following:
A kind of measurement mechanism of differential capacitance type instrument; It is characterized in that; Comprise alternation excitation signal generator, line select switch circuit, AD converter and digital signal processor; Through the line select switch circuit positive incentive and reverse energization to the differential capacitance type instrument are realized in the two ends that said alternation pumping signal is applied to the differential capacitance type instrument after the alternation pumping signal of said alternation excitation signal generator generation fixed frequency fixed amplitude; The output terminal of the middle plate of differential capacitance type instrument connects AD converter and digital signal processor successively; The output signal of the middle plate of differential capacitance type instrument carries out signals collecting through AD converter during with positive incentive and reverse energization; Carried out the FFT spectrum analysis and extracted the amplitude maximal value respectively by digital signal processor again, the amplitude maximal value that positive incentive and reverse energization are obtained is done the difference back and is obtained the variable quantity of the measurand of differential capacitance type instrument, the measurement of realization differential capacitance type instrument according to certain linear.
Said alternation excitation signal generator comprises microcontroller and DA converter, and said microcontroller is exported the sequence of values of layout according to certain rules and controlled the alternation pumping signal of DA converter output fixed frequency fixed amplitude.
Said line select switch circuit comprises the electronic switch by microprocessor controls, and the state of said microprocessor controls electronic switch is realized positive incentive and the reverse energization to the differential capacitance type instrument.
Also comprise signal amplifier and low-pass filter; The output terminal of the middle plate of said differential capacitance type instrument is connected AD converter through behind signal amplifier and the low-pass filter earlier successively again, and the output signal of the middle plate of differential capacitance type instrument carries out carrying out signals collecting through AD converter again after signal amplification and the low-pass filtering treatment with positive incentive and reverse energization the time.
Said digital signal processor links to each other with microcontroller; The amplitude maximal value that said digital signal processor extracts respectively after with the FFT spectrum analysis inputs to microcontroller; The amplitude maximal value that microcontroller obtains positive incentive and reverse energization is done the difference back and is obtained the variable quantity of the measurand of differential capacitance type instrument according to certain linear, realizes the measurement of differential capacitance type instrument; And/or said microcontroller is a single-chip microcomputer; And/or said AD converter is the high-precision high-speed AD converter.
A kind of measuring method of differential capacitance type instrument; It is characterized in that; Positive incentive and reverse energization to the differential capacitance type instrument are realized in forward and the two ends that oppositely are applied to the differential capacitance type instrument respectively with the alternation pumping signal of fixed frequency fixed amplitude; The output signal of the middle plate of differential capacitance type instrument carries out signals collecting after digital signal processor carries out the FFT spectrum analysis through AD converter during respectively with positive incentive and reverse energization; And extract the amplitude maximal value respectively; The amplitude maximal value that positive incentive and reverse energization are obtained is done the difference back and is obtained the variable quantity of the measurand of differential capacitance type instrument according to certain linear, realizes the measurement of differential capacitance type instrument.
Export the sequence of values of layout according to certain rules and control the alternation pumping signal that the DA converter is exported the fixed frequency fixed amplitude through microcontroller.
State through the microprocessor controls electronic switch is realized positive incentive and reverse energization to the differential capacitance type instrument with alternation pumping signal forward and oppositely be applied to the two ends of differential capacitance type instrument respectively.
The output signal of the middle plate of differential capacitance type instrument carries out earlier carrying out signals collecting through AD converter again after signal amplification and the low-pass filtering treatment when said positive incentive and reverse energization.
The amplitude maximal value that said digital signal processor extracts respectively after with the FFT spectrum analysis inputs to microcontroller; The amplitude maximal value that positive incentive and reverse energization is obtained by microcontroller is done the difference back and is obtained the variable quantity of the measurand of differential capacitance type instrument according to certain linear, realizes the measurement of differential capacitance type instrument; And/or said microcontroller is a single-chip microcomputer; And/or said AD converter is the high-precision high-speed AD converter.
Technique effect of the present invention is following:
The measurement mechanism of the differential capacitance type instrument that the present invention relates to; Comprise alternation excitation signal generator, line select switch circuit, AD converter and digital signal processor; Realize positive incentive and reverse energization through alternation excitation signal generator and line select switch circuit to the differential capacitance type instrument; The output signal of the middle plate of the differential capacitance type instrument of when positive incentive and reverse energization, drawing respectively all is two output signals that comprised the converted quantity information of measurand; Signal be should export and AD converter and digital signal processor passed through respectively successively; AD converter carries out signals collecting; After digital signal processor adopts the data processing of FFT technology completion to the spectrum analysis result of measurand; The amplitude maximal value of extracting is the amplitude of the dominant frequency signal in the frequency spectrum, can eliminate the influence of other frequency component to measurement result fully, has antijamming capability very well; Therefore can obtain more accurately, more stable measurement result, avoided the pairing changes in capacitance in the direct measurement differential capacitive sensor that prior art adopts can be because the influence of disturbing factor cause obtaining the problem of high precision and high reliability measurement result.In addition; The amplitude maximal value that positive incentive and reverse energization obtain is done the difference back obtains the measurand of differential capacitance type instrument according to certain linear variable quantity; For the differential capacitance type instrument of appointment; The scale-up factor of this linear relationship is the calibration value that dispatches from the factory, and is known quantity, and it is poor that the amplitude maximal value that positive incentive and reverse energization are obtained is done; Can eliminate the offset voltage that when differential capacitor formula instrument is undesirable, causes, further improve the accuracy and the reliability of differential capacitance type instrument output outcome measurement value.
The alternation excitation signal generator is set comprises microcontroller and DA converter; Microcontroller is exported the sequence of values of layout according to certain rules and is controlled the alternation pumping signal of DA converter output fixed frequency fixed amplitude; Adopt microcontroller to carry out ordered control; Can avoid exporting the problem of the uncontrollable and frequency drift of the amplitude of signal; Guarantee that the DA converter produces high-quality exciting signal source, promptly the DA converter can be exported the alternation pumping signal of fixed frequency, fixed amplitude, for accurately measuring the differential capacitance type instrument prerequisite guarantee is provided.
The line select switch circuit is set comprises electronic switch by microprocessor controls; State through the microprocessor controls electronic switch is realized positive incentive and reverse energization to the differential capacitance type instrument; Can realize alternately switching automatically between positive incentive and the reverse energization; And making that the line select switch circuit structure is simple, microprocessor controls is precisely convenient, so reduced cost and guaranteed the accuracy of measuring.
Through signalization amplifier and low-pass filter; The output signal of the middle plate of the differential capacitance type instrument of drawing respectively during with positive incentive and reverse energization carries out signal and amplifies and low-pass filtering treatment; Can eliminate the influence of some higher harmonic components of this output signal to measurement result; Improve antijamming capability, improved measuring accuracy simultaneously.
The measuring method of the differential capacitance type instrument that the present invention relates to; Positive incentive and reverse energization to the differential capacitance type instrument are realized in forward and the two ends that oppositely are applied to the differential capacitance type instrument respectively with the alternation pumping signal of fixed frequency fixed amplitude; The output signal of the pairing electric capacity middle plate of the differential capacitance type instrument under the situation of two kinds of excitations carries out signals collecting after digital signal processor carries out the FFT spectrum analysis through AD converter; Utilized the FFT technology to accomplish data processing to measured result; After FFT handles, can extract the dominant frequency signal amplitude exactly, have antijamming capability very well; The dominant frequency signal amplitude maximal value that after spectrum analysis, obtains under two kinds of excitation situation is done the variable quantity that difference calculates measurand; Can further eliminate offset voltage; So measuring method according to the invention than conventional measurement can obtain more accurately, more stable measurement result, guarantee to satisfy of the strict demand of Geotechnical Engineering safety monitoring field to the accuracy of the reliability of safety monitoring instrument and measurement data.
Description of drawings
Fig. 1 is a differential capacitance type instrument positive incentive equivalent circuit diagram.
Fig. 2 is a differential capacitance type instrument reverse energization equivalent circuit diagram.
Fig. 3 is the front end preferred structure synoptic diagram of the measurement mechanism of differential capacitance type instrument of the present invention.
Fig. 4 is the rear end preferred structure synoptic diagram of the measurement mechanism of differential capacitance type instrument of the present invention.
Fig. 5 is differential capacitance type instrument middle plate output signal Spectrum Analysis figure as a result.
Fig. 6 is the preferred flow charts of the measuring method of differential capacitance type instrument of the present invention.
Embodiment
The present invention will be described below in conjunction with accompanying drawing.
The invention discloses a kind of measurement mechanism of differential capacitance type instrument, the measurand of this measurement mechanism is a differential capacitor formula instrument, and this differential capacitive sensor (is defined as C by the pairing electric capacity of a pair of parameter symmetry
1And C
2) as the sensitive element of this sensor.This measurement mechanism comprises alternation excitation signal generator, line select switch circuit, AD converter and digital signal processor, and wherein, the alternation excitation signal generator produces the alternation pumping signal U of fixed frequency fixed amplitude
iThe line select switch circuit is passed through with said alternation pumping signal U in the back
iPositive incentive and reverse energization to the differential capacitance type instrument are realized in the two ends that are applied to the differential capacitance type instrument, and the equivalent circuit diagram of this differential capacitance type instrument positive incentive and reverse energization is as depicted in figs. 1 and 2 respectively, wherein S
1And S
2Be respectively the time output signal of drawing from the middle plate output line of the pairing electric capacity of differential capacitance type instrument to differential capacitance type instrument positive incentive and reverse energization.Fig. 3 is the front end preferred structure synoptic diagram of measurement mechanism according to the invention; In this embodiment; The alternation excitation signal generator comprises microcontroller and DA converter, and wherein microcontroller can be chosen as single-chip microcomputer or other type microcontroller, and the reference voltage of DA converter is V
Ref, the sequence of values of exporting layout according to certain rules by single-chip microcomputer among Fig. 3 is to form amplitude control figure amount, the alternation pumping signal U of control DA converter output fixed frequency f, fixed amplitude A
i, as differential capacitance type instrument pairing capacitor C
1And C
2Pumping signal, alternation pumping signal U
iThe not strict qualification of shape, can be shapes such as square wave, triangular wave or sawtooth wave, the alternation pumping signal of preferred sine wave shape.The line select switch circuit can be chosen as the electronic switch by microcontroller (like the single-chip microcomputer of present embodiment) control, can certainly select other electronic switch or relay switch or other on-off circuit.The state of Single-chip Controlling electronic switch is realized positive incentive and the reverse energization to the differential capacitance type instrument.Particularly, electronic switch comprises the electronic switch SW of two alternatives
1And SW
2, SW
1Pin 1 be respectively power end and earth terminal with pin 2, the level height CS of pin 3 switches; SW
2Pin 1 be respectively earth terminal and power end with pin 2, the level height CS of pin 3 switches.SW wherein
1Pin 1 and SW
2Pin 2 all with pumping signal U
iBe connected SW
1Pin 2 and SW
2Pin 1 all be connected SW with signal ground
1The capacitor C of pin 3 and differential capacitance type instrument
1Electrode be connected SW
2The capacitor C of pin 3 and differential capacitance type instrument
2Electrode be connected SW
1, SW
2Receive the Switch Control signal controlling that single-chip microcomputer sends and synchronization action is worked as SW
1On off state be pin 1 when being communicated with pin 3, SW
2On off state also be that pin 1 is communicated with pin 3.Work as SW
1On off state be pin 2 when being communicated with pin 3, SW
2On off state also be that pin 2 is communicated with pin 3.Switch Control signal K in the present embodiment can realize control (like certain I/O mouth on off state of control single chip computer) by single-chip microcomputer (or other type microcontroller), when K is high level, and SW
1, SW
2On off state be pin 1 and be communicated with pin 3, so when K is low level, SW
1, SW
2On off state be pin 2 and be communicated with pin 3.
Under the ordered control of single-chip microcomputer (or other type microcontroller), the alternation pumping signal U of a fixed frequency fixed amplitude of DA converter output
i, as differential capacitance type instrument pairing capacitor C
1And C
2Pumping signal.Be high level by Single-chip Controlling Switch Control signal K earlier, make SW
1, SW
2On off state be that pin 1 is communicated with pin 3, to realize the positive incentive of differential capacitance type instrument.Promptly this moment this alternation pumping signal U
iAct on C
1Electrode on, C simultaneously
2Electrode connect signal ground, we are defined as the positive incentive of differential capacitance type instrument such energisation mode, the equivalent electrical circuit of this positive incentive is as shown in Figure 1.At alternation pumping signal U
iEffect under, the middle plate extension line place of differential capacitance type instrument can produce an output signal S who has comprised the variable quantity information (△ F) of measurand
1
The output terminal of the middle plate of differential capacitance type instrument connects signal amplifier, low-pass filter, AD converter and digital signal processor successively through extension line, the rear end preferred structure synoptic diagram of the measurement mechanism of differential capacitance type instrument of the present invention as shown in Figure 4.Wherein, signal amplifier and low-pass filter are preferred components, and promptly the output terminal of the middle plate of differential capacitance type instrument can directly connect AD converter.In the embodiment shown in fig. 4, the output signal S of the middle plate of differential capacitance type instrument during positive incentive
1Obtain amplifying through signal amplifier earlier; Carry out the purified treatment of signal again through low-pass filter; Signal after the purified treatment is carried out signals collecting through AD converter, and AD converter obtains digitizing measured value sequence, after obtaining enough collection samples; Accomplish FFT (Fast Fourier Transform by digital signal processor (DSP); FFT) handle, it is as shown in Figure 5 to obtain the spectrum analysis result data, in the spectrum analysis result data, extracts amplitude maximal value M (amplitude of dominant frequency signal f in the frequency spectrum) note and makes N
1And preserve, accomplished the forward measuring process.
Be low level by Single-chip Controlling Switch Control signal K again, make SW
1, SW
2On off state be that pin 2 is communicated with pin 3, to realize the reverse energization of differential capacitance type instrument.Promptly change alternation pumping signal U
iActive position, with alternation pumping signal U
iAct on C
2Electrode on, C simultaneously
1Electrode connect signal ground, we are defined as the reverse energization of differential capacitance type instrument such energisation mode, the equivalent electrical circuit of this reverse energization is as shown in Figure 2.At alternation pumping signal U
iEffect under, the middle plate extension line place of differential capacitance type instrument also can produce an output signal S who has comprised the variable quantity information (△ F) of measurand
2
The rear end preferred structure synoptic diagram of the measurement mechanism of differential capacitance type instrument of the present invention same as shown in Figure 4, the output signal S of the middle plate of differential capacitance type instrument during reverse energization
2Obtain amplifying through signal amplifier earlier; Carry out the purified treatment of signal again through low-pass filter, the signal after the purified treatment is carried out signals collecting through AD converter, AD converter obtains digitizing measured value sequence; After obtaining enough collection samples; Accomplish FFT by digital signal processor (DSP) and handle, obtain spectrum analysis result data as shown in Figure 5, in the spectrum analysis result data, extract amplitude maximal value M (amplitude of dominant frequency signal f in the frequency spectrum) note and make N
2And preserve, accomplished reverse measuring process.
Obtain N respectively at positive incentive and reverse energization
1And N
2After, because output signal S
1And S
2The variable quantity information (△ F) that has all comprised measurand is so this output signal is accomplished the N that directly obtains after FFT handles through amplification, LPF, AD conversion and DSP
1And N
2The variable quantity information (△ F) that also comprises measurand, in case after signal amplifier, low-pass filter and AD converter are confirmed, △ F and N
1, N
2Between just have the corresponding relation of confirming, can be by expression formula Δ F=k (N
1-N
2) expression, for the differential capacitance type instrument of appointment, the k value can obtain through demarcating before dispatching from the factory, so k is a known quantity.So obtained N
1And N
2Measured value, just can realize measurement function through calculate obtaining △ F value to the variable quantity △ F of measurand.Certainly, with the amplitude maximal value N that obtains
1And N
2The calculating of doing the variable quantity of difference back obtains the differential capacitance type instrument according to certain linear measurand can be calculated by single-chip microcomputer (the perhaps microcontroller of other type) and obtained; Also can directly calculate the numerical value that obtains △ F, thereby measurement mechanism of the present invention is accomplished the measuring process of the differential capacitance type instrument of one whole by digital signal processor (DSP).
Fig. 3 and Fig. 4 constitute the preferred measurement mechanism of the present invention jointly; This measurement mechanism produces high-quality alternation exciting signal source through single-chip microcomputer and DA converter are set; Adopt digital signal processor (DSP) utilization FFT technology to accomplish data processing simultaneously to measured result; After FFT handles; Can extract the dominant frequency signal amplitude exactly; Have very good antijamming capability, it is poor that the amplitude maximal value that positive incentive and reverse energization are obtained is done, can eliminate the offset voltage that when differential capacitor formula instrument is undesirable, causes (offset voltage that just positive incentive and reverse energization is all produced through do difference calculate cancel out each other); Make that this measurement mechanism can obtain more accurately, more stable measurement result, guarantee to satisfy of the strict demand of Geotechnical Engineering safety monitoring field the accuracy of the reliability of safety monitoring instrument and measurement data.For increasing the actual measurement effect; Preferred AD converter is the high-precision high-speed AD converter; Simultaneously preferred DA converter and high-precision high-speed AD converter adopt same reference voltage voltage as a reference, and the input/output relation that can guarantee the differential capacitance type instrument like this is not because the changes in amplitude of alternation pumping signal is introduced measuring error.
The invention still further relates to a kind of measuring method of differential capacitance type instrument; Positive incentive and reverse energization to the differential capacitance type instrument are realized in forward and the two ends that oppositely are applied to the differential capacitance type instrument to this method respectively with the alternation pumping signal of fixed frequency fixed amplitude; The output signal of the middle plate of differential capacitance type instrument carries out signals collecting after digital signal processor carries out the FFT spectrum analysis through AD converter during respectively with positive incentive and reverse energization; And extract the amplitude maximal value respectively; The amplitude maximal value that positive incentive and reverse energization are obtained is done the difference back and is obtained the variable quantity of the measurand of differential capacitance type instrument according to certain linear, realizes the measurement of differential capacitance type instrument.The preferred flow charts of this measuring method is as shown in Figure 6.
A, export the sequence of values of layout according to certain rules and control the alternation pumping signal U of DA converter output fixed frequency fixed amplitude through microcontroller (like single-chip microcomputer)
iAlternation pumping signal U
iCan be shapes such as sine wave, square wave, triangular wave or sawtooth wave.
B, the state through the microprocessor controls electronic switch are realized the positive incentive to the differential capacitance type instrument alternation pumping signal Ui forward is applied to the two ends of differential capacitance type instrument.The practical implementation electrical block diagram can be as shown in Figure 3, and the Switch Control signal K of microprocessor controls electronic switch is a high level, makes SW
1, SW
2On off state be pin 1 and be communicated with pin 3, this moment this alternation pumping signal U
iAct on C
1Electrode on, C simultaneously
2Electrode connect signal ground, the positive incentive equivalent electrical circuit of this differential capacitance type instrument is as shown in Figure 1.
C, at alternation pumping signal U
iEffect under, the middle plate extension line place of differential capacitance type instrument can produce an output signal S who has comprised the variable quantity information (△ F) of measurand
1
D, output signal S
1Carry out after the purified treatment of signal through signal amplification, LPF; Realize data acquisition by high-precision high-speed AD converter conversion back; After after obtaining enough sampled data samples, accomplishing the FFT spectrum analysis by digital signal processor (DSP) again; Obtain the spectrum analysis result data, in the spectrum analysis result data, extract amplitude maximal value N
1And preserve, thereby accomplish the forward measuring process.The practical implementation electrical block diagram can be as shown in Figure 4.
E, change alternation pumping signal U
iActive position, the state through the microprocessor controls electronic switch is with alternation pumping signal U
iOppositely be applied to the two ends of differential capacitance type instrument, realize reverse energization the differential capacitance type instrument.The practical implementation electrical block diagram can be as shown in Figure 3, and the Switch Control signal K of Single-chip Controlling electronic switch is a low level, makes SW
1, SW
2On off state be pin 2 and be communicated with pin 3, this moment this alternation pumping signal U
iAct on C
2Electrode on, C simultaneously
1Electrode connect signal ground, the reverse energization equivalent electrical circuit of this differential capacitance type instrument is as shown in Figure 2.
F, at alternation pumping signal U
iEffect under, the middle plate extension line place of differential capacitance type instrument produces an output signal S who has comprised the variable quantity information (△ F) of measurand
2
G, output signal S
2Carry out after the purified treatment of signal through signal amplification, LPF; Realize data acquisition by high-precision high-speed AD converter conversion back; After after obtaining enough sampled data samples, accomplishing the FFT spectrum analysis by digital signal processor (DSP) again; Obtain the spectrum analysis result data, in the spectrum analysis result data, extract amplitude maximal value N
2And preserve, thereby accomplish reverse measuring process.The practical implementation electrical block diagram can be as shown in Figure 4.
H, at the amplitude maximal value N that obtains to obtain by positive incentive and reverse energization
1And N
2After, by microcontroller (perhaps still by digital signal processor DSP) with N
1And N
2Do the numerical value of the variable quantity △ F of difference back obtains the differential capacitance type instrument according to certain linear measurand, realize the measurement of differential capacitance type instrument.For the differential capacitance type instrument of appointment, the k value can obtain through demarcating before dispatching from the factory, so k is a known quantity.△ F and N
1, N
2Between corresponding relation that exist to confirm, can be by expression formula Δ F=k (N
1-N
2) expression, so obtained N
1And N
2Measured value, just can realize measurement function through calculate obtaining △ F value, the measuring process of completion one whole to the variable quantity △ F of measurand.
Certainly no matter be measurement mechanism of the present invention or measuring method; All can exchange the positive incentive of differential capacitance type instrument and the sequencing of reverse energization; Promptly can implement reverse energization to the differential capacitance type instrument earlier; The middle plate of differential capacitance type instrument output signal is carried out subsequent parts handle and obtain the amplitude maximal value and preserve, accomplish oppositely and measure; To differential capacitance type instrument enforcement positive incentive, same middle plate output signal with the differential capacitance type instrument carries out the subsequent parts processing and obtains amplitude maximal value and preservation again, and the completion forward is measured; Reverse measure with forward measure all accomplishes after, two amplitude maximal values that will obtain are again done after the difference numerical value of variable quantity △ F that obtains the measurand of differential capacitance type instrument according to certain linear, the measurement of realization differential capacitance type instrument.
Should be pointed out that the above embodiment can make those skilled in the art more fully understand the invention, but do not limit the present invention in any way creation.Therefore; Although this instructions has carried out detailed explanation with reference to accompanying drawing and embodiment to the invention,, those skilled in the art are to be understood that; Still can make amendment or be equal to replacement the invention; In a word, all do not break away from the technical scheme and the improvement thereof of the spirit and the scope of the invention, and it all should be encompassed in the middle of the protection domain of the invention patent.
Claims (10)
1. the measurement mechanism of a differential capacitance type instrument; It is characterized in that; Comprise alternation excitation signal generator, line select switch circuit, AD converter and digital signal processor; Through the line select switch circuit positive incentive and reverse energization to the differential capacitance type instrument are realized in the two ends that said alternation pumping signal is applied to the differential capacitance type instrument after the alternation pumping signal of said alternation excitation signal generator generation fixed frequency fixed amplitude; The output terminal of the middle plate of differential capacitance type instrument connects AD converter and digital signal processor successively; The output signal of the middle plate of differential capacitance type instrument carries out signals collecting through AD converter during with positive incentive and reverse energization; Carried out the FFT spectrum analysis and extracted the amplitude maximal value respectively by digital signal processor again, the amplitude maximal value that positive incentive and reverse energization are obtained is done the difference back and is obtained the variable quantity of the measurand of differential capacitance type instrument, the measurement of realization differential capacitance type instrument according to certain linear.
2. the measurement mechanism of differential capacitance type instrument according to claim 1; It is characterized in that; Said alternation excitation signal generator comprises microcontroller and DA converter, and said microcontroller is exported the sequence of values of layout according to certain rules and controlled the alternation pumping signal of DA converter output fixed frequency fixed amplitude.
3. the measurement mechanism of differential capacitance type instrument according to claim 2; It is characterized in that; Said line select switch circuit comprises the electronic switch by microprocessor controls, and the state of said microprocessor controls electronic switch is realized positive incentive and the reverse energization to the differential capacitance type instrument.
4. the measurement mechanism of differential capacitance type instrument according to claim 3; It is characterized in that; Also comprise signal amplifier and low-pass filter; The output terminal of the middle plate of said differential capacitance type instrument is connected AD converter through behind signal amplifier and the low-pass filter earlier successively again, and the output signal of the middle plate of differential capacitance type instrument carries out carrying out signals collecting through AD converter again after signal amplification and the low-pass filtering treatment with positive incentive and reverse energization the time.
5. the measurement mechanism of differential capacitance type instrument according to claim 4; It is characterized in that; Said digital signal processor links to each other with microcontroller; The amplitude maximal value that said digital signal processor extracts respectively after with the FFT spectrum analysis inputs to microcontroller, and the amplitude maximal value that microcontroller obtains positive incentive and reverse energization is done the difference back and obtained the variable quantity of the measurand of differential capacitance type instrument according to certain linear, realizes the measurement of differential capacitance type instrument; And/or said microcontroller is a single-chip microcomputer; And/or said AD converter is the high-precision high-speed AD converter.
6. the measuring method of a differential capacitance type instrument; It is characterized in that; Positive incentive and reverse energization to the differential capacitance type instrument are realized in forward and the two ends that oppositely are applied to the differential capacitance type instrument respectively with the alternation pumping signal of fixed frequency fixed amplitude; The output signal of the middle plate of differential capacitance type instrument carries out signals collecting after digital signal processor carries out the FFT spectrum analysis through AD converter during respectively with positive incentive and reverse energization; And extract the amplitude maximal value respectively; The amplitude maximal value that positive incentive and reverse energization are obtained is done the difference back and is obtained the variable quantity of the measurand of differential capacitance type instrument according to certain linear, realizes the measurement of differential capacitance type instrument.
7. the measuring method of differential capacitance type instrument according to claim 6 is characterized in that, exports the sequence of values of layout according to certain rules and controls the alternation pumping signal that the DA converter is exported the fixed frequency fixed amplitude through microcontroller.
8. the measuring method of differential capacitance type instrument according to claim 7; It is characterized in that; State through the microprocessor controls electronic switch is realized positive incentive and reverse energization to the differential capacitance type instrument with alternation pumping signal forward and oppositely be applied to the two ends of differential capacitance type instrument respectively.
9. the measuring method of differential capacitance type instrument according to claim 8; It is characterized in that the output signal of the middle plate of differential capacitance type instrument carries out earlier carrying out signals collecting through AD converter again after signal amplification and the low-pass filtering treatment when said positive incentive and reverse energization.
10. the measuring method of differential capacitance type instrument according to claim 9; It is characterized in that; The amplitude maximal value that said digital signal processor extracts respectively after with the FFT spectrum analysis inputs to microcontroller; The amplitude maximal value that positive incentive and reverse energization is obtained by microcontroller is done the difference back and is obtained the variable quantity of the measurand of differential capacitance type instrument according to certain linear, realizes the measurement of differential capacitance type instrument; And/or said microcontroller is a single-chip microcomputer; And/or said AD converter is the high-precision high-speed AD converter.
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| CN2012101816395A Pending CN102706383A (en) | 2012-06-04 | 2012-06-04 | Measurement device and method for differential capacitance type instrument |
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| CN106291116A (en) * | 2016-09-20 | 2017-01-04 | 江南工业集团有限公司 | A kind of resistance measuring instrument |
| CN106312306A (en) * | 2016-10-20 | 2017-01-11 | 大族激光科技产业集团股份有限公司 | Height adjusting system and method for laser cutting head |
| CN106660169A (en) * | 2014-08-13 | 2017-05-10 | 通快激光与系统工程有限公司 | Method for determining distance correction values during the laser machining of a workpiece and associated laser machine tool |
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