CN202693026U - Measuring device of differential capacitive instrument - Google Patents
Measuring device of differential capacitive instrument Download PDFInfo
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- CN202693026U CN202693026U CN 201220260819 CN201220260819U CN202693026U CN 202693026 U CN202693026 U CN 202693026U CN 201220260819 CN201220260819 CN 201220260819 CN 201220260819 U CN201220260819 U CN 201220260819U CN 202693026 U CN202693026 U CN 202693026U
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- capacitance type
- type instrument
- differential capacitance
- converter
- differential
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Abstract
The utility model relates to a measuring device of a differential capacitive instrument. The measuring device comprises an alternating excitation signal generator, a circuit selection switch circuit, an analog-to-digital (AD) converter and a digital signal processor. The alternating excitation signal generator generates alternating excitation signals with fixed frequency and affixed amplitude, and the alternating excitation signals are applied on two ends of the differential capacitive instrument by the circuit selection switch circuit to achieve positive direction excitation and negative direction excitation of the differential capacitive instrument. The output end of a middle pole plate of the differential capacitive instrument is sequentially connected with the AD converter and the digital signal processor. Subtraction of frequency spectrum data amplitude maximums obtained by conversion of output signals of the middle pole plate of the differential capacitive instrument in the positive direction excitation and the negative direction excitation is conducted, and variation of measured physical quantity of the differential capacitive instrument is obtained according to certain linear relation to achieve measurement of the differential capacitive instrument. The measuring device ensures that the differential capacitive instrument obtains high-accuracy measuring result and improves reliability of a differential resistance sensor.
Description
Technical field
The utility model relates to the measurement mechanism of the differential capacitance type instrument in the Safety Monitoring Instruments 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 Instruments type, general settlement measurement, the vertical line displacement measurement that is used for realizing static liquid level, draw the monitoring of the physical quantitys such as bracing cable displacement measurement, thermometal mark deformation monitoring, more application is arranged in safety monitoring project.
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 is another capacitor C with it
2The appearance value △ C that diminishes, C
1With C
2The variation difference of electric capacity 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, thus the Changing Pattern of measurand F just can be obtained by measuring 2 △ C, thus analyze the healthy and safe situation of judging Geotechnical Engineering.
On measuring principle, the metering circuit of differential capacitive sensor is very simple, is that AC signal is converted into direct current signal, and uses Ohm law by the direct-flow output signal U at electric capacity two ends
0With ac-excited signal U
0iBetween the voltage amplitude ratio relation just can realize direct measurement to capacitance △ C.As
But in fact owing to the numerical value very little (generally at this order of magnitude of tens PF) of △ C, the interference that any link of metering circuit is introduced all can cause measured value inaccurate, such as the distributed capacitance of wire, the noise of components and parts etc.Therefore, the high precision of differential capacitance type instrument, high reliability measurement relatively 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 for the differential capacitance type instrument designs a kind of brand-new measuring system, in the hope of obtaining ideal measurement sensitivity and measuring accuracy.
The utility model content
The utility model can't obtain the problem of high precision and high reliability measurement result owing to the impact of disturbing factor for existing differential capacitance type instrument, a kind of measurement mechanism of novel differential capacitance type instrument is provided, this device can overcome various interference to the impact of the measurement result of differential capacitor instrument effectively by the FFT technology, guarantees that the differential capacitance type instrument obtains the high-acruracy survey result.
The technical solution of the utility model is as follows:
A kind of measurement mechanism of differential capacitance type instrument, it is characterized in that, comprise the alternation excitation signal generator, the line select switch circuit, AD converter and digital signal processor, by the line select switch circuit described alternation pumping signal is applied to the two ends realization of differential capacitance type instrument to positive incentive and the reverse energization of differential capacitance type instrument after the alternation pumping signal of described 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 is carried out signals collecting by AD converter during with positive incentive and reverse energization, carry out the FFT spectrum analysis and extract respectively the amplitude maximal value by digital signal processor again, the amplitude maximal value that positive incentive and reverse energization are obtained is done and is obtained the variable quantity of the measurand of differential capacitance type instrument according to certain linear relationship after poor, realizes the measurement of differential capacitance type instrument.
Described alternation excitation signal generator comprises microcontroller and DA converter, and described microcontroller is exported the sequence of values of according to certain rules layout and controlled the alternation pumping signal of DA converter output fixed frequency fixed amplitude.
Described line select switch circuit comprises the electronic switch by microprocessor controls, and the state of described 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 described differential capacitance type instrument is connected with low-pass filter through signal amplifier successively first and is connected AD converter again, with positive incentive and reverse energization the time output signal of the middle plate of differential capacitance type instrument carry out that signal amplifies and low-pass filtering treatment after carry out signals collecting by AD converter again.
Described digital signal processor links to each other with microcontroller, the amplitude maximal value that described 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 and is obtained the variable quantity of the measurand of differential capacitance type instrument according to certain linear relationship after poor, realizes the measurement of differential capacitance type instrument.
Described microcontroller is single-chip microcomputer.
Described AD converter is the high-precision high-speed AD converter.
Technique effect of the present utility model is as follows:
The measurement mechanism of the differential capacitance type instrument that the utility model relates to, comprise the alternation excitation signal generator, the line select switch circuit, AD converter and digital signal processor, realize positive incentive and reverse energization to the differential capacitance type instrument by alternation excitation signal generator and line select switch circuit, the output signal of the middle plate of the differential capacitance type instrument of drawing respectively when positive incentive and reverse energization all is two output signals that comprised the converted quantity information of measurand, this output signal is passed through respectively AD converter and digital signal processor successively, AD converter is carried out signals collecting, after digital signal processor adopts the FFT technology to finish the data of the result of spectrum analysis of measurand are processed, the amplitude maximal value of extracting is the amplitude of the dominant frequency signal in the frequency spectrum, can eliminate other frequency component fully to the impact of measurement result, has very well antijamming capability, therefore it is more accurate to obtain, more stable measurement result has avoided the variation meeting of the pairing electric capacity in the direct measurement differential capacitive sensor that prior art adopts because the impact of disturbing factor causes obtaining the problem of high precision and high reliability measurement result.In addition, the amplitude maximal value that positive incentive and reverse energization are obtained is done and is obtained the variable quantity of the measurand of differential capacitance type instrument according to certain linear relationship after poor, 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, be known quantity, 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 accuracy and the reliability of differential capacitance type instrument Output rusults measured value, guaranteed to satisfy the Geotechnical Monitoring field to the strict demand of the accuracy of the reliability of Safety Monitoring Instruments and measurement data.
The alternation excitation signal generator is set comprises microcontroller and DA converter, microcontroller is exported the sequence of values of according to certain rules layout and is controlled the alternation pumping signal of DA converter output fixed frequency fixed amplitude, adopt microcontroller to control in order, can avoid the problem of the uncontrollable and frequency drift of the amplitude of output signal, guarantee that the DA converter produces high-quality exciting signal source, be the alternation pumping signal that the DA converter can be exported fixed frequency, fixed amplitude, for Measurement accuracy differential capacitance type instrument provides the prerequisite guarantee.
The line select switch circuit is set comprises electronic switch by microprocessor controls, state by the microprocessor controls electronic switch is realized positive incentive and the reverse energization to the differential capacitance type instrument, can realize automatically alternately switching between positive incentive and the reverse energization, and so that the line select switch circuit structure is simple, microprocessor controls is precisely convenient, so reduced cost and guaranteed the accuracy of measuring.
By 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 is carried out signal and is amplified and low-pass filtering treatment, can eliminate some higher harmonic components of this output signal to the impact of measurement result, improve antijamming capability, improved simultaneously measuring accuracy.
Description of drawings
Fig. 1 is differential capacitance type instrument positive incentive equivalent circuit diagram.
Fig. 2 is differential capacitance type instrument reverse energization equivalent circuit diagram.
Fig. 3 is the front end preferred structure synoptic diagram of the measurement mechanism of the utility model differential capacitance type instrument.
Fig. 4 is the rear end preferred structure synoptic diagram of the measurement mechanism of the utility model differential capacitance type instrument.
Fig. 5 is the result of spectrum analysis figure of differential capacitance type instrument middle plate output signal.
Embodiment
Below in conjunction with accompanying drawing the utility model is described.
The utility model 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 rear line select switch circuit that passes through is with described alternation pumping signal U
iBe applied to the two ends realization of differential capacitance type instrument to positive incentive and the reverse energization of differential capacitance type instrument, the equivalent circuit diagram of this differential capacitance type instrument positive incentive and reverse energization is distinguished as depicted in figs. 1 and 2, wherein S
1And S
2Be respectively to differential capacitance type instrument positive incentive and reverse energization the time output signal of drawing from the middle plate output line of the pairing electric capacity of differential capacitance type instrument.Fig. 3 is the front end preferred structure synoptic diagram of measurement mechanism described in the utility model, 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, export the sequence of values of according to certain rules layout to form amplitude control figure amount, the alternation pumping signal U of control DA converter output fixed frequency f, fixed amplitude A by single-chip microcomputer among Fig. 3
i, as differential capacitance type instrument pairing capacitor C
1And C
2Pumping signal, alternation pumping signal U
iShape strictly do not limit, can be the 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 (such as 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 and pin 2 be respectively power end and earth terminal, the level of pin 3 height gauge tap is switched; SW
2Pin 1 and pin 2 be respectively earth terminal and power end, the level of pin 3 height gauge tap is switched.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
2Be subjected to 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 (such as 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 orderly 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 first, 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.Namely 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 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 by extension line, the rear end preferred structure synoptic diagram of the measurement mechanism of the utility model differential capacitance type instrument as shown in Figure 4.Wherein, signal amplifier and low-pass filter are preferred components, and namely 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 by signal amplifier first, carry out again the purified treatment of signal through low-pass filter, signal after the purified treatment is carried out signals collecting by AD converter, AD converter obtains digitizing measured value sequence, after obtaining enough collecting samples, finish FFT(Fast Fourier Transform by digital signal processor (DSP), fast fourier transform) processes, obtain the result of spectrum analysis data as shown in Figure 5, go out the amplitude of dominant frequency signal f in the amplitude maximal value M(frequency spectrum in the result of spectrum analysis extracting data) be denoted as N
1And preserve, finished 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.Namely 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 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 the utility model differential capacitance type instrument equally as shown in Figure 4, the output signal S of the middle plate of differential capacitance type instrument during reverse energization
2Obtain amplifying by signal amplifier first, carry out again the purified treatment of signal through low-pass filter, signal after the purified treatment is carried out signals collecting by AD converter, AD converter obtains digitizing measured value sequence, after obtaining enough collecting samples, finish FFT by digital signal processor (DSP) and process, obtain result of spectrum analysis data as shown in Figure 5, go out the amplitude of dominant frequency signal f in the amplitude maximal value M(frequency spectrum in the result of spectrum analysis extracting data) be denoted as N
2And preserve, finished reverse measuring process.
Obtain respectively N 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 finished the N that directly obtains after FFT processes through amplification, low-pass filtering, 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 determined, △ F and N
1, N
2Between just have the corresponding relation of determining, 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 by demarcating before dispatching from the factory, so k is a known quantity.So obtained N
1And N
2Measured value, just can by calculate obtaining △ F value, realize the measurement function to the variable quantity △ F of measurand.Certainly, with the amplitude maximal value N that obtains
1And N
2Doing the calculating of variable quantity that obtains the measurand of differential capacitance type instrument according to certain linear relationship after poor can be calculated by single-chip microcomputer (the perhaps microcontroller of other type) and obtain, also can directly calculate the numerical value that obtains △ F by digital signal processor (DSP), thereby the utility model measurement mechanism is finished once the measuring process of complete differential capacitance type instrument.
Fig. 3 and Fig. 4 consist of the preferred measurement mechanism of the utility model jointly, this measurement mechanism produces high-quality alternation exciting signal source by single-chip microcomputer and DA converter are set, adopting simultaneously digital signal processor (DSP) to use the FFT technology to finish processes the data of measured result, after FFT processes, can extract exactly the dominant frequency signal amplitude, has 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 namely positive incentive and reverse energization is all produced is cancelled out each other by doing poor calculating), so that this measurement mechanism can obtain is more accurate, more stable measurement result guarantees to satisfy the Geotechnical Monitoring field to the strict demand of the accuracy of the reliability of Safety Monitoring Instruments 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 as reference voltage, can guarantee that like this input/output relation of differential capacitance type instrument is not because the changes in amplitude of alternation pumping signal is introduced measuring error.
Certain measurement mechanism of the present utility model can exchange the positive incentive of differential capacitance type instrument and the sequencing of reverse energization, namely can implement reverse energization to the differential capacitance type instrument first, the middle plate output signal of differential capacitance type instrument is carried out the subsequent parts processing obtain amplitude maximal value and preservation, finish reverse measurement; Again the differential capacitance type instrument is implemented positive incentive, equally the middle plate output signal of differential capacitance type instrument is carried out the subsequent parts processing and obtain amplitude maximal value and preservation, finish forward and measure; oppositely measure and forward measure all finish after, two amplitude maximal values that will obtain are again done and are obtained the numerical value of variable quantity △ F of the measurand of differential capacitance type instrument, the measurement of realization differential capacitance type instrument according to certain linear relationship after poor.
Should be pointed out that the above embodiment can make the invention of those skilled in the art's comprehend, but do not limit the present invention in any way creation.Therefore; although this instructions has been described in detail the invention with reference to drawings and Examples; but; 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 technical scheme and the improvement thereof of the spirit and scope of the invention, and it all should be encompassed in the middle of the protection domain of the invention patent.
Claims (7)
1. the measurement mechanism of a differential capacitance type instrument, it is characterized in that, comprise the alternation excitation signal generator, the line select switch circuit, AD converter and digital signal processor, by the line select switch circuit described alternation pumping signal is applied to the two ends realization of differential capacitance type instrument to positive incentive and the reverse energization of differential capacitance type instrument after the alternation pumping signal of described 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 is carried out signals collecting by AD converter during with positive incentive and reverse energization, carry out the FFT spectrum analysis and extract respectively the amplitude maximal value by digital signal processor again, the amplitude maximal value that positive incentive and reverse energization are obtained is done and is obtained the variable quantity of the measurand of differential capacitance type instrument according to certain linear relationship after poor, realizes the measurement of differential capacitance type instrument.
2. the measurement mechanism of differential capacitance type instrument according to claim 1, it is characterized in that, described alternation excitation signal generator comprises microcontroller and DA converter, and described microcontroller is exported the sequence of values of according to certain rules layout 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, described line select switch circuit comprises the electronic switch by microprocessor controls, and the state of described 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 described differential capacitance type instrument is connected with low-pass filter through signal amplifier successively first and is connected AD converter again, with positive incentive and reverse energization the time output signal of the middle plate of differential capacitance type instrument carry out that signal amplifies and low-pass filtering treatment after carry out signals collecting by AD converter again.
5. the measurement mechanism of differential capacitance type instrument according to claim 4, it is characterized in that, described digital signal processor links to each other with microcontroller, the amplitude maximal value that described 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 and is obtained the variable quantity of the measurand of differential capacitance type instrument according to certain linear relationship after poor, realizes the measurement of differential capacitance type instrument.
6. the measurement mechanism of differential capacitance type instrument according to claim 4 is characterized in that, described microcontroller is single-chip microcomputer.
7. the measurement mechanism of differential capacitance type instrument according to claim 4 is characterized in that, described AD converter is the high-precision high-speed AD converter.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220260819 CN202693026U (en) | 2012-06-04 | 2012-06-04 | Measuring device of differential capacitive instrument |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220260819 CN202693026U (en) | 2012-06-04 | 2012-06-04 | Measuring device of differential capacitive instrument |
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| Publication Number | Publication Date |
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| CN202693026U true CN202693026U (en) | 2013-01-23 |
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| CN 201220260819 Expired - Lifetime CN202693026U (en) | 2012-06-04 | 2012-06-04 | Measuring device of differential capacitive instrument |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102706383A (en) * | 2012-06-04 | 2012-10-03 | 基康仪器(北京)有限公司 | Measurement device and method for differential capacitance type instrument |
-
2012
- 2012-06-04 CN CN 201220260819 patent/CN202693026U/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102706383A (en) * | 2012-06-04 | 2012-10-03 | 基康仪器(北京)有限公司 | Measurement device and method for differential capacitance type instrument |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| C56 | Change in the name or address of the patentee |
Owner name: JIKANG INSTRUMENT CO., LTD. Free format text: FORMER NAME: JIKANG INSTRUMENT(BEIJING) CO., LTD. |
|
| CP01 | Change in the name or title of a patent holder |
Address after: 102401, 3, Binhe West Street, Triumph Street, Beijing, Fangshan District, Liangxiang Patentee after: CHINA GEOKON INSTRUMENTS CO., LTD. Address before: 102401, 3, Binhe West Street, Triumph Street, Beijing, Fangshan District, Liangxiang Patentee before: Jikang Instrument(Beijing) Co., Ltd. |
|
| CX01 | Expiry of patent term |
Granted publication date: 20130123 |
|
| CX01 | Expiry of patent term |