CN113515062A - High-precision LVDT measuring circuit and measuring method - Google Patents
High-precision LVDT measuring circuit and measuring method Download PDFInfo
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- CN113515062A CN113515062A CN202010281919.8A CN202010281919A CN113515062A CN 113515062 A CN113515062 A CN 113515062A CN 202010281919 A CN202010281919 A CN 202010281919A CN 113515062 A CN113515062 A CN 113515062A
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B19/00—Programme-control systems
- G05B19/02—Programme-control systems electric
- G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
- G05B19/042—Programme control other than numerical control, i.e. in sequence controllers or logic controllers using digital processors
- G05B19/0423—Input/output
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/003—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring position, not involving coordinate determination
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/20—Pc systems
- G05B2219/21—Pc I-O input output
- G05B2219/21137—Analog to digital conversion, ADC, DAC
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Abstract
The invention discloses a high-precision LVDT measuring circuit and a measuring method, which comprises a displacement sensor LVDT, a single chip microcomputer circuit, a reference circuit, an amplifier circuit, a voltage filter circuit and a filter circuit, wherein when in use, a sine wave excitation signal of the novel high-precision LVDT measuring circuit and the measuring method adopts 12-bit DA, 14-bit AD acquisition, 0.5 thousandth of precision of the reference and 10ppm temperature drift, so that the temperature drift of the whole hardware circuit is smaller, the precision is higher, and the whole circuit has the main cost of a single chip microcomputer and peripheral operational amplifier because the DA and the AD are integrated in the single chip microcomputer, the whole cost is within 20 yuan, the whole cost is basically equal to that of a traditional discrete device scheme and is far lower than that of an integrated IC scheme, and digital measurement is carried out through a software algorithm, so different LVDTs, different excitation frequencies and amplitudes only need to modify the software parameters, so that a very flexible and accurate adaptation to different LVDT sensors is possible.
Description
Technical Field
The invention belongs to the technical field of related industrial field linear displacement sensors, and particularly relates to a high-precision LVDT measuring circuit and a measuring method.
Background
LVDT is an abbreviation of linear variable differential transformer, belonging to the linear displacement transducer. The working principle is simply that of a movable iron core transformer. The sensor comprises a primary coil and a secondary coil, and the accurate position of a sensor iron core can be obtained through a measuring circuit. The method has the advantages of no friction measurement, nearly infinite mechanical life, infinite resolution, good repeatability, environmental adaptability and the like. LVDT is widely used to measure precise data on the elongation, vibration frequency, amplitude, thickness and expansion of an object.
The basic principle of the LVDT measuring circuit is to give a sinusoidal excitation at the primary coil, then demodulate the signal at the secondary coil, and measure the position of the core according to the demodulated signal amplitude. A typical measurement circuit would include a voltage regulator circuit, a sine wave generator, a demodulator and an amplifier.
The traditional circuit adopts a discrete device scheme, a Venturi bridge oscillation generating circuit is used for generating sine waves, demodulation is carried out through a diode structure, and finally amplification and filtering processing is carried out through an operational amplifier. The scheme has low cost, but because the precision and the temperature drift of the capacitor depended on by the sine wave generating circuit are relatively poor relative to other devices, and the influence of the temperature on the voltage drop of the diode in the demodulation circuit is large, the precision of the circuit is difficult to ensure in the full working temperature range.
Some of the integrated ICs currently available, such as NE5521 from Philips and AD598/698 from ADI, have integrated the measurement circuit. The method has good precision and stability, but the cost is very high. Discrete devices measure only less than about 20 dollars in cost, while ADI's AD698 chips exceed one hundred dollars.
In addition, the optimum response frequency and amplitude of different types of LVDTs are different. Both in the conventional discrete device circuit scheme and the integrated IC scheme, the frequency and amplitude of the generated excitation signal are fixed and thus cannot be adapted to the optimum state. In addition, when the LVDTs are densely arranged, the excitation frequency needs to be adjusted in order to suppress co-channel interference, which is difficult to achieve by traditional discrete device and integrated IC schemes.
Disclosure of Invention
The invention aims to provide a high-precision LVDT measuring circuit and a measuring method, which aim to solve the problems that the existing measuring mode proposed in the background technology has low precision and higher cost, and can not flexibly match with the LVDT characteristics.
In order to achieve the purpose, the invention provides the following technical scheme:
a high-precision LVDT measuring circuit and method comprises a displacement sensor LVDT, a single chip microcomputer circuit, a reference circuit, an amplifier circuit, a voltage filter circuit and a filter circuit, the single chip microcomputer is internally integrated with a high-speed AD (analog-to-digital conversion) circuit and a high-speed DA circuit (digital-to-analog conversion), the single chip microcomputer is responsible for operation, a primary coil sine wave voltage DA is generated, and a secondary coil voltage AD is acquired, the reference circuit provides an AD, the DA circuit provides a precise reference source, the amplifier circuit comprises a DA signal amplification circuit and an AD signal amplification circuit, the DA signal amplification circuit amplifies the amplitude of an excitation signal to the required value of the LVDT, the AD signal amplification circuit amplifies the voltage of a secondary coil to the sampling range of the AD circuit, the filter circuit comprises an excitation signal filter and a secondary signal filter, the excitation filter circuit is used for eliminating steps in signal waveforms, and the secondary signal filter is used for eliminating burrs in the signal waveforms.
Preferably, the sinusoidal excitation signal of the primary coil is directly generated by a DA conversion circuit.
Preferably, the signal demodulation of the secondary coil is directly performed by an AD conversion circuit to sample the original sinusoidal signal, and a rectification detection circuit is not needed.
Preferably, the single chip microcomputer generates a sine table through digital calculation according to the frequency amplitude of the excitation signal, drives the DA conversion circuit to output sine voltage, multiplies the frequency of the voltage value of the AD conversion circuit by 64 times, calculates the RMS value after filtering by software, and finally converts the RMS value into the position of the iron core.
Preferably, the sine excitation signal of the DA conversion circuit is obtained by generating a sine table through digital calculation of a single chip microcomputer.
Preferably, the secondary signal measurement is mathematically calculated to obtain the RMS value by means of oversampling by the AD circuit.
Preferably, the amplitude and the frequency of the sinusoidal signal can be generated by digital calculation according to the set frequency and the amplitude parameter of the LVDT excitation signal, and the LVDT excitation signal can be automatically generated by recalculation after the parameter of the LVDT excitation signal is modified.
Preferably, the oversampling multiple used for the secondary signal measurement is 64, which is a value obtained by comprehensively considering the chip performance and the sampling precision, and reducing the oversampling coefficient reduces the sampling precision and also reduces the amount of computation, and the sampling multiple can be adjusted between 32 and 256.
Compared with the prior art, the invention provides a high-precision LVDT measuring circuit and a measuring method, which have the following beneficial effects:
1. the sine wave excitation signal of the high-precision LVDT measuring circuit and the measuring method of the invention uses 12-bit DA, 14-bit AD acquisition, 0.5 thousandth of standard precision and 10ppm temperature drift, so that the temperature drift of the whole hardware circuit is smaller and the precision is higher.
2. The circuit of the high-precision LVDT measuring circuit and the measuring method has the main cost of the single chip microcomputer and peripheral operational amplifier because the DA and the AD are integrated in the single chip microcomputer, the overall cost is within 20 yuan, and the circuit is basically equivalent to the traditional discrete device scheme and is far lower than the integrated IC scheme.
3. The circuit and the method for measuring the high-precision LVDT are used for carrying out digital measurement through a software algorithm, so that different LVDTs and different excitation frequencies and amplitudes can be obtained only by modifying software parameters, and different LVDT sensors can be flexibly and accurately adapted.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention without limiting the invention in which:
FIG. 1 is a schematic diagram of a high-precision LVDT measuring circuit and method according to the present invention;
FIG. 2 is a schematic diagram of an initialization process of the high-precision LVDT measuring circuit and the measuring method according to the present invention;
FIG. 3 is a schematic diagram of the interrupt handling of the timer of the high-precision LVDT measuring circuit and the measuring method according to the present invention;
FIG. 4 is a schematic diagram of the main loop processing of the high precision LVDT measurement circuit and the measurement method according to the present invention;
in the figure: 1. an LVDT; 2. a single chip circuit; 2-1, a DA circuit in the single chip microcomputer; 2-2, an AD circuit in the single chip microcomputer; 3-1, an excitation filter circuit; 3-2, a secondary signal filter circuit; 4-1, an excitation signal amplifying circuit; 4-2, a secondary signal amplifying circuit; 5. a reference circuit.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1-4, the present invention provides a technical solution:
a high-precision LVDT measuring circuit and method comprises a displacement sensor LVDT, a single chip microcomputer circuit and a reference circuit, the voltage amplifier comprises an excitation signal filter circuit and a secondary signal filter circuit, the excitation filter circuit is used for eliminating steps in signal waveforms, and the secondary signal filter circuit is used for eliminating burrs in the signal waveforms.
Further, the sinusoidal excitation signal of the primary coil is directly generated by the DA conversion circuit.
Furthermore, the signal demodulation of the secondary coil directly samples the original sinusoidal signal by the AD conversion circuit without a rectification detection circuit.
Further, the singlechip generates a sine table through digital calculation according to the frequency amplitude of the excitation signal, drives the DA conversion circuit to output sine voltage, and carries out frequency multiplication and oversampling on the voltage value of the AD conversion circuit by 64 times, and the RMS value is calculated after software filtering and finally converted into the position of the iron core.
Furthermore, the sine excitation signal of the DA conversion circuit is obtained by generating a sine table through digital calculation of a single chip microcomputer.
Furthermore, the secondary signal measurement adopts the mode of AD circuit oversampling to calculate the RMS value mathematically.
Furthermore, the amplitude and the frequency of the sinusoidal signal can be generated by digital calculation according to the set LVDT excitation signal frequency and amplitude parameter, and the LVDT excitation signal parameter can be automatically generated by recalculation after being modified.
Furthermore, the oversampling multiple adopted by the secondary signal measurement is 64, which is a value taking the performance of the chip and the sampling precision into consideration comprehensively, and reducing the oversampling coefficient can reduce the sampling precision and also can reduce the operation amount, and the ordinary sampling multiple can be adjusted between 32 and 256.
The working principle and the using process of the invention are as follows: the high-precision LVDT measuring method comprises the following steps:
the method comprises the following steps: and the circuit singlechip calculates a 64-frequency-multiplication sine wave DA code according to the LVDT excitation frequency and amplitude parameters and the reference voltage.
Step two: and refreshing the DA codes to the DA conversion circuit of the singlechip in the timed interruption.
Step three: and the secondary voltage obtained by the acquisition AD circuit is interrupted by 64 times of frequency in the timer interruption.
Step four: the RMS calculation is performed on the collected secondary voltages.
Step five: the RMS value is divided by the excitation amplitude, and the resulting coefficient is proportional to the core position.
Step six: and before the system runs, the proportional relation between the coefficient and the position of the iron core is obtained through position calibration.
Step seven: and solving the position of the iron core according to the obtained coefficient and the proportional relation obtained by calibration.
As shown in figure 1, the measuring circuit of the LVDT of the device comprises a 1-LVDT circuit, a 2-single chip microcomputer circuit, a 2-1 single chip microcomputer internal DA circuit, a 2-2 single chip microcomputer internal AD circuit, a 3-1 excitation filter circuit, a 3-2 secondary signal filter circuit, a 4-1 excitation signal amplifying circuit, a 4-2 secondary signal amplifying circuit and a 5-reference circuit. The singlechip 2 is internally integrated with a high-speed AD circuit 2-1 and a high-speed DA circuit 2-2. The singlechip 2 generates a sine DA code table according to the accessed reference 5 and LVDT excitation signal parameters (typically 2.5Khz/3 Vrms), the DA code is output to the DA circuit 2-1, sine wave voltage generated by the DA circuit 2-1 is accessed to the 3-1 excitation filter circuit for low-pass filtering, steps in the signal are eliminated, and the sine signal is smoothed. The filtered sinusoidal signal is connected to a driver amplifier 4-1, becomes a signal of about 3Vrms and is connected to a primary coil of the LVDT 1. Meanwhile, a secondary coil of the LVDT 1 induces a secondary signal in a linear relation with the position of the iron core, the secondary signal is connected to a secondary signal filter circuit 3-2 to filter out noise waves, the signal is connected to a secondary signal amplifying circuit 4-2 to be conditioned into a signal of 0-3.3V, a 2-2 AD sampling circuit is connected to carry out sampling, and the single chip microcomputer 1 calculates a voltage RMS value after acquiring a sampling value and finally calculates the position of the valve core.
In view of fig. 2, 3 and 4, as shown in fig. 2, the 2-1 single chip microcomputer executes an initialization process, and calculates a DA code table according to the set frequency and amplitude of the LVDT excitation signal and the reference voltage value in a manner of brushing 64 points per cycle. And initializes the AD, DA, timer (10.4 us). Excitation frequency is 2.5KHZ, DA refresh frequency is 96K, and AD oversampling rate is 96K.
And in the 2-2 singlechip timer interruption in fig. 3, 1 DA channel is refreshed according to the DA code table every time, and 1 sampled AD channel value is read.
In the main cycle of the 2-3 single chip microcomputer in fig. 4, abnormal value filtering is performed according to the AD sampling value, the RMS value is calculated, the calculated RMS value is divided by the set excitation amplitude value, the coefficient is calculated, and finally the core position corresponding to the coefficient is converted from the calibrated position. And simultaneously, detecting whether a calibration request exists in the main cycle, if so, calibrating, and respectively recording the zero coefficient value and the full coefficient value of the iron core.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (8)
1. A high-precision LVDT measuring circuit and a measuring method thereof comprise a displacement sensor LVDT, a single chip microcomputer circuit, a reference circuit, an amplifier circuit, a voltage filter circuit and a filter circuit, and are characterized in that: the single chip microcomputer is internally integrated with a high-speed AD (analog-to-digital conversion) circuit and a high-speed DA circuit (digital-to-analog conversion), the single chip microcomputer is responsible for operation, a primary coil sine wave voltage DA is generated, and a secondary coil voltage AD is acquired, the reference circuit provides an AD, the DA circuit provides a precise reference source, the amplifier circuit comprises a DA signal amplification circuit and an AD signal amplification circuit, the DA signal amplification circuit amplifies the amplitude of an excitation signal to the required value of the LVDT, the AD signal amplification circuit amplifies the voltage of a secondary coil to the sampling range of the AD circuit, the filter circuit comprises an excitation signal filter and a secondary signal filter, the excitation filter circuit is used for eliminating steps in signal waveforms, and the secondary signal filter is used for eliminating burrs in the signal waveforms.
2. The high-precision LVDT measurement circuit and method according to claim 1, wherein: the sinusoidal excitation signal of the primary coil is directly generated by a DA conversion circuit.
3. The high-precision LVDT measurement circuit and method according to claim 1, wherein: the signal demodulation of the secondary coil is directly performed by sampling the original sinusoidal signal through an AD conversion circuit, and a rectification detection circuit is not needed.
4. The high-precision LVDT measurement circuit and method according to claim 1, wherein: the single chip microcomputer generates a sine table through digital calculation according to the frequency amplitude of the excitation signal, drives the DA conversion circuit to output sine voltage, performs frequency multiplication oversampling on the voltage value of the AD conversion circuit by 64 times, calculates the RMS value after filtering by software, and finally converts the RMS value into the position of the iron core.
5. The high-precision LVDT measurement circuit and method according to claim 1, wherein: the sine excitation signal of the DA conversion circuit is obtained by generating a sine table through digital calculation of a single chip microcomputer.
6. The high-precision LVDT measurement circuit and method according to claim 1, wherein: and the secondary signal measurement adopts an AD circuit oversampling mode to calculate the RMS value through mathematical calculation.
7. The high-precision LVDT measurement circuit and method according to claim 1, wherein: the amplitude and the frequency of the sinusoidal signal can be generated by digital calculation according to the set LVDT excitation signal frequency and amplitude parameter, and the LVDT excitation signal parameter can be generated by automatic recalculation after being modified.
8. The high-precision LVDT measurement circuit and method according to claim 1, wherein: the over-sampling multiple adopted by the secondary signal measurement is 64, which is a value comprehensively considering the performance of the chip and the sampling precision, the sampling precision can be reduced by reducing the over-sampling coefficient, the operation amount can be reduced, and the general sampling multiple can be adjusted between 32 and 256.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114136345A (en) * | 2021-11-26 | 2022-03-04 | 南京晨光集团有限责任公司 | LVDT/RVDT analog demodulation circuit |
| CN114264322A (en) * | 2021-12-15 | 2022-04-01 | 四川大学 | Full-digital demodulation system, method and device, electronic equipment and storage medium |
| CN114413738A (en) * | 2021-12-13 | 2022-04-29 | 贵州振华风光半导体股份有限公司 | Signal acquisition system for LVDT and RVDT displacement sensors |
Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20080000258A (en) * | 2006-06-27 | 2008-01-02 | 주식회사 지오네트 | Lvdt signal converter of using asic |
| CN102818513A (en) * | 2012-07-31 | 2012-12-12 | 沈阳黎明航空发动机(集团)有限责任公司 | Demodulating device of linear variable differential transformer, and soft demodulating method thereof |
| CN205561866U (en) * | 2016-01-20 | 2016-09-07 | 西安强源电气有限公司 | LVDTRVDT modem |
| CN106370096A (en) * | 2016-09-23 | 2017-02-01 | 中国科学院苏州生物医学工程技术研究所 | Measurement circuit and measuring method of LVDT (Linear Variable Differential Transformer) |
| CN106813564A (en) * | 2015-11-30 | 2017-06-09 | 杭州奥莫自动化科技有限公司 | A kind of LVDT displacement transducers digitalized processing method and device |
| CN209326558U (en) * | 2019-01-30 | 2019-08-30 | 北京航顺泰达科技发展有限公司 | LVDT displacement sensor Performance Test System |
| CN110398196A (en) * | 2019-07-19 | 2019-11-01 | 陕西威尔机电科技有限公司 | A kind of LVDT sensor signal processing method and system for accurate measurement |
| CN209877876U (en) * | 2019-07-12 | 2019-12-31 | 成都恩菲特科技有限公司 | LVDT/RVDT sensor measuring card |
| CN209991929U (en) * | 2019-05-09 | 2020-01-24 | 深圳市森瑟科技发展有限公司 | Measuring circuit of linear displacement sensor of LVDT |
-
2020
- 2020-04-11 CN CN202010281919.8A patent/CN113515062A/en active Pending
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20080000258A (en) * | 2006-06-27 | 2008-01-02 | 주식회사 지오네트 | Lvdt signal converter of using asic |
| CN102818513A (en) * | 2012-07-31 | 2012-12-12 | 沈阳黎明航空发动机(集团)有限责任公司 | Demodulating device of linear variable differential transformer, and soft demodulating method thereof |
| CN106813564A (en) * | 2015-11-30 | 2017-06-09 | 杭州奥莫自动化科技有限公司 | A kind of LVDT displacement transducers digitalized processing method and device |
| CN205561866U (en) * | 2016-01-20 | 2016-09-07 | 西安强源电气有限公司 | LVDTRVDT modem |
| CN106370096A (en) * | 2016-09-23 | 2017-02-01 | 中国科学院苏州生物医学工程技术研究所 | Measurement circuit and measuring method of LVDT (Linear Variable Differential Transformer) |
| CN209326558U (en) * | 2019-01-30 | 2019-08-30 | 北京航顺泰达科技发展有限公司 | LVDT displacement sensor Performance Test System |
| CN209991929U (en) * | 2019-05-09 | 2020-01-24 | 深圳市森瑟科技发展有限公司 | Measuring circuit of linear displacement sensor of LVDT |
| CN209877876U (en) * | 2019-07-12 | 2019-12-31 | 成都恩菲特科技有限公司 | LVDT/RVDT sensor measuring card |
| CN110398196A (en) * | 2019-07-19 | 2019-11-01 | 陕西威尔机电科技有限公司 | A kind of LVDT sensor signal processing method and system for accurate measurement |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114136345A (en) * | 2021-11-26 | 2022-03-04 | 南京晨光集团有限责任公司 | LVDT/RVDT analog demodulation circuit |
| CN114413738A (en) * | 2021-12-13 | 2022-04-29 | 贵州振华风光半导体股份有限公司 | Signal acquisition system for LVDT and RVDT displacement sensors |
| CN114264322A (en) * | 2021-12-15 | 2022-04-01 | 四川大学 | Full-digital demodulation system, method and device, electronic equipment and storage medium |
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Application publication date: 20211019 |