CN108333437A - Micro capacitance system and measurement method - Google Patents
Micro capacitance system and measurement method Download PDFInfo
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- CN108333437A CN108333437A CN201810136512.9A CN201810136512A CN108333437A CN 108333437 A CN108333437 A CN 108333437A CN 201810136512 A CN201810136512 A CN 201810136512A CN 108333437 A CN108333437 A CN 108333437A
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
- G01R27/2605—Measuring capacitance
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Abstract
The invention discloses a kind of micro capacitance systems, it includes a signal generating module, one capacitance/voltage transformation module, one signal acquisition process module, one CPU and a communication module, the signal generating module includes DDS sinusoidal signal generators and digital analog converter, the signal acquisition process module includes programmable amplifier, analog-digital converter and digital demodulator, the DDS sinusoidal signal generators output end is sequentially connected in series digital analog converter, capacitance/voltage transformation module, programmable amplifier, analog-digital converter, digital demodulator and CPU, the other end signal input port of the digital demodulator connects DDS sinusoidal signal generators, the CPU also respectively with DDS sinusoidal signal generators, programmable amplifier and communication module are connected.The particle charge interference problem that micro capacitance system of the present invention can overcome charge injection, null offset and measurement object when being Gas-solid Two-phase Flow, improves measurement accuracy.The present invention also provides a kind of micro capacitance methods.
Description
Technical field
The present invention relates to two phase flow quality measurement technique field more particularly to a kind of micro capacitance system and measurement sides
Method.
Background technology
With the rapid development of industrial technology and scientific level, the Gas-solid Two-phase Flow containing powder particle is in national economy
It becomes more and more important with the status in human lives.Powder pneumatic conveying system is widely used in chemical industry, metallurgy, power, light industry and army
Gong Deng departments, the problem related with powder carry also result in the attention of people.Due to flowing over for industrial gas-particle two-phase fluid
Journey is complicated, it is difficult to find its flowing law, the measurement in modern industry field, the mass flow of gas-particle two-phase fluid becomes one ten
Important project, many researchers of industrially developed country is divided to do a lot of work, had developed such as impulse force formula, differential pressure thus
The flow measurement device of formula, thermal balance type, but all there is limitations for these devices, it could not extensive use in the industrial production.
Condenser type Dual-Phrase Distribution of Gas olid mass flowmenter is a kind of measuring technique for measuring Dual-Phrase Distribution of Gas olid mass flow, is had
Feature simple in structure, of low cost is convenient for commercial Application.Condenser type Dual-Phrase Distribution of Gas olid mass flowmenter mainly by sensor,
Measuring system and data processing system composition.Its basic functional principle is that electricity is installed on the outside of the pipeline that gas-particle two-phase fluid flows
Hold sensor.Since the substance of each split-phase of two-phase fluid in pipeline is different, there is different dielectric constants, work as fluid stream
It crosses between capacitor plate when being formed by detecting field, since the variation of phase concentration can cause the variation of the effective dielectric constant of fluid,
To make the capacitance output valve of sensor change correspondingly.Therefore, the size of capacitance can be used as the quality stream of Dual-Phrase Distribution of Gas olid
Amount.Measured capacitance values are generally in 0.01pF to the measurement between 1pF, belonging to weak capacitive in the system, and therefore, small capacitance is surveyed
Amount is one of critical issue in condenser type gas-particle two-phase mass flow meter systems.
And most common Micro-capacitance measuring circuit mainly has two kinds of charge and discharge electrical method and alternating current method, charge and discharge electrical method capacitance measurement
The advantages that circuit is of simple structure and low cost with its, low in energy consumption and be used for capacitance detecting earliest, but it has compared with alternating current method
There is the problems such as null offset and charge are injected, easily causes measured deviation.When measurement object is gas-particle two-phase fluid, particle lotus
Electrical phenomena will cause to induce certain charge on sensor electrode, defeated to generate certain voltage in measuring circuit
Go out, certain influence can be brought to capacitance measurement in this way, can even measuring system be made to fail sometimes, restricts small capacitance detection
Precision further increases.
In consideration of it, a kind of small it is necessary to provide measured deviation solving drawbacks described above and high certainty of measurement small capacitance
Measuring system and measurement method.
Invention content
A technical problem to be solved by this invention provides that a kind of measured deviation is small and the small capacitance of high certainty of measurement
Measuring system.
It is inclined to reduce measurement that another technical problem to be solved by this invention is to provide a kind of micro capacitance method
Difference improves measurement accuracy.
In order to solve the above technical problems, the present invention uses technical solution as described below：The present invention provides a kind of small electric
Hold measuring system, for connecting control system or data receiving system, the micro capacitance system includes a signal
Module occurs, for generating pumping signal comprising DDS sinusoidal signal generators and digital analog converter, the DDS sinusoidal signals
Generator is used to generate the DDS sinusoidal signal generators for generating digital sine pumping signal, the digital analog converter
Digital sine pumping signal be converted to analog sine pumping signal；One capacitance/voltage transformation module, for sending out the signal
The pumping signal that raw module generates is transformed to AC measurment voltage signal；One signal acquisition process module, for acquiring the electricity
The AC measurment voltage signal of appearance/voltage transformation module conversion acquisition is simultaneously handled it comprising programmable amplifier, digital-to-analogue
Converter and digital demodulator, the programmable amplifier is for zooming in and out the AC measurment voltage signal, the modulus
AC measurment voltage signal after converter is used to scale the programmable amplifier is converted into digital measurement voltage signal, described
Digital demodulator is used to encourage letter according to the digital sine that the digital measurement voltage signal and DDS sinusoidal signal generators generate
It number is demodulated, obtains the amplitude result of relationship proportional to measured capacitance；One CPU is generated for controlling signal generating module
Pumping signal；Work for the programmable amplifier for controlling signal acquisition process module；For obtaining and sending the digital solution
Adjust the amplitude result of the relationship proportional to measured capacitance obtained after device demodulation；One communication module, for acquisition and measured capacitance
The amplitude result of proportional relationship is simultaneously exported to the control system or data receiving system.
Its further technical solution is：The capacitance/voltage transformation module include a capacitance sensor and with the electricity
Hold the conversion circuit for the capacitance that the capacitance sensor detects to be converted to voltage of the detecting electrode connection of sensor, institute
It includes an operational amplifier, a feedback capacity and a feedback resistance to state conversion circuit, and the detecting electrode of the capacitance sensor connects
It is connected on the inverting input of the operational amplifier, the positive input end grounding of the operational amplifier, output end, which is used as, to be turned
The output end of circuit is changed, one end is connected with the output end of operational amplifier after the feedback resistance and feedback capacity parallel connection, another
One end is connected with the inverting input of operational amplifier.
Its further technical solution is：The digital analog converter is the DAC cores with 65MHz sample rates and 14 bit resolutions
Piece, the analog-digital converter are the ADC chips with 65MHz sample rates and 14 bit resolutions.
Its further technical solution is：The signal generating module further includes a low-pass filter, for the digital-to-analogue
The analog sine pumping signal that converter conversion obtains is filtered.
Its further technical solution is：The low-pass filter is the second-order low-pass filter of Sallen-Key structures,
Cutoff frequency is 600KHz.
Its further technical solution is：The DDS sinusoidal signal generators, CPU, digital demodulator and communication module by
FPGA is realized.
In order to solve the above technical problems, the present invention also provides a kind of micro capacitance methods comprising following steps：
CPU controls signal generating module and generates pumping signal；
Capacitance/voltage transformation module receives the pumping signal that the signal generating module provides, according to the excitation received
Signal acquisition AC measurment voltage signal；
Signal acquisition process module acquires the AC measurment voltage signal that the capacitance/voltage transformation module obtains and to it
It is handled, obtains the amplitude result of relationship proportional to measured capacitance；
CPU obtains the amplitude as a result, and sending it to communication module；
Communication module exports the amplitude result to control system or data receiving system.
Its further technical solution is：The CPU controls signal generating module generates pumping signal and includes the following steps：
CPU controls DDS sinusoidal signal generators and generates digital sine pumping signal；
Digital analog converter is converted to analog sine pumping signal according to the digital sine pumping signal；
Low-pass filter is filtered the analog sine pumping signal.
Its further technical solution is：The signal acquisition process module acquires the capacitance/voltage transformation module and obtains
AC measurment voltage signal and it is handled, the amplitude result for obtaining proportional to measured capacitance relationship includes following step
Suddenly：
CPU control programmable amplifiers acquire the AC measurment voltage signal that the capacitance/voltage transformation module obtains, to institute
AC measurment voltage signal is stated to zoom in and out；
AC measurment voltage signal after analog-digital converter scales the programmable amplifier is converted into digital measurement voltage
Signal；
Digital demodulator obtains the digital sine that the digital measurement voltage signal and DDS sinusoidal signal generators generate and swashs
Signal is encouraged, and multiplying is carried out according to the digital measurement voltage signal and digital sine pumping signal, is obtained and tested electricity
The amplitude result of Rongcheng proportionate relationship.
Its further technical solution is：The digital demodulator obtains the digital measurement voltage signal and DDS sines letter
The digital sine pumping signal that number generator generates, and according to the digital measurement voltage signal and digital sine pumping signal into
Row multiplying, the amplitude result for obtaining relationship proportional to measured capacitance include the following steps：
Digital demodulator needs digital measurement electricity to be used when demodulation every time is arranged according to the accuracy and speed demand of measurement
The sampling number N for pressing signal, samples the digital measurement voltage signal, obtains Sampling Measurement Data；
Digital demodulator gives birth to DDS sinusoidal signal generators within a complete signal period according to the sampling number N
At digital sine pumping signal sampled, obtain its with mutually and orthogonal reference signal data, and will it is described with mutually with reference to letter
Number and orthogonal reference signal data carry out multiplying with Sampling Measurement Data respectively, obtain corresponding same phase product signal
Data and Orthogonal Multiplication signal data；
Digital demodulator adds up N number of same phase product signal data in a complete signal period of acquisition, obtains
It takes same phase product signal and N number of Orthogonal Multiplication signal data in a complete signal period of acquisition adds up, obtains
Orthogonal Multiplication signal and；
Digital demodulator according to the same phase product signal and and Orthogonal Multiplication signal and obtain it is proportional to measured capacitance
The amplitude result of relationship.
The beneficial technical effect of the present invention lies in：Micro capacitance system of the present invention is sent out by the way that DDS sinusoidal signals are arranged
To generate digital stimulus signal, the charge injection and null offset for overcoming capacitance measurement to generate reduce measured deviation, pass through raw device
Programmable amplifier passes through after being zoomed in and out to AC measurment voltage signal and carries out analog-to-digital conversion by analog-digital converter, so that collected
Signal has best signal-to-noise ratio, carries out multiplying and demodulation process to collected signal using digital demodulator, obtains
The amplitude of relationship proportional to measured capacitance is as a result, to realize the measurement of capacitance.Micro capacitance method of the present invention passes through
The particle that the mode of digital actuation and digital demodulation overcomes charge injection, null offset and measurement object when being Gas-solid Two-phase Flow
Charge interference problem improves measurement accuracy, reduces measured deviation, it is ensured that the reliability and accuracy of capacitance measurement.
Description of the drawings
Fig. 1 is the structural framing schematic diagram of one specific embodiment of micro capacitance system of the present invention.
Fig. 2 is the circuit diagram of capacitance/voltage transformation module of measuring system shown in Fig. 1.
Fig. 3 is the flow chart of one specific embodiment of micro capacitance method of the present invention.
Fig. 4 is the flow chart of the digital demodulation of micro capacitance method of the present invention.
Specific implementation mode
To make those skilled in the art that the object, technical solutions and advantages of the present invention be more clearly understood, with
Under the present invention is further elaborated in conjunction with the accompanying drawings and embodiments.Obviously, will be described below embodiment is only the present invention
A part of the embodiment, instead of all the embodiments.Based on the embodiments of the present invention, those of ordinary skill in the art are not having
The every other embodiment obtained under the premise of creative work is made, shall fall within the protection scope of the present invention.
Micro capacitance system of the present invention for connecting control system or data receiving system, by acquisition with it is tested
The amplitude result of the proportional relationship of capacitance exports to control system or data receiving system and obtains corresponding electricity with analyzing processing
Hold size, realizes the measurement to capacitance.
Referring to Fig.1, micro capacitance system 10 of the present invention includes a signal generating module 110, one capacitance/voltage transformation
Module 120, a signal acquisition process module 130, a CPU140 and a communication module 150.The signal generating module 110 includes
DDS sinusoidal signal generators 111 and digital analog converter 112, the signal acquisition process module 130 include programmable amplifier 131,
Analog-digital converter 132 and digital demodulator 133.
The signal generating module 110 is for generating pumping signal, and the DDS sinusoidal signal generators 111 are for generating
Digital sine pumping signal, the number that the digital analog converter 112 is used to generate the DDS sinusoidal signal generators 111 is just
String pumping signal is converted to analog sine pumping signal.Traditional charging/discharging type pumping signal is replaced using digital stimulus signal,
It can overcome the problems, such as charge injection and null offset, reduce measured deviation.In the present embodiment, the DDS sinusoidal signals occur
Device 111 is the DDS sinusoidal signal generators for the simplification for not having frequency adjustable function that digital signal processing method is realized, is had
The stability of high frequency and amplitude, is conducive to the stability of raising system.
The capacitance/voltage transformation module 120 is used to obtain the pumping signal of the generation of the signal generating module 110, and
Transform it into AC measurment voltage signal.The signal acquisition process module 130 is for acquiring the capacitance/voltage transformation mould
The AC measurment voltage signal of the conversion acquisition of block 120 is simultaneously handled it, wherein the programmable amplifier 131 is to the electricity
The AC measurment voltage signal that appearance/transformation of voltage transformation module 120 obtains suitably is scaled, and is turned so as to finally enter modulus
The AC measurment voltage signal of parallel operation 132 has the amplitude range for being most suitable for acquisition, best to make collected signal have
Signal-to-noise ratio, measurement dynamic range is big.The analog-digital converter 132 is used for the exchange after the scaling of the programmable amplifier 131
Measurement voltage signal is converted into digital measurement voltage signal, and the digital demodulator 133 is used for according to the digital measurement voltage
The digital sine pumping signal that signal and DDS sinusoidal signal generators 111 generate is demodulated, and is obtained proportional to measured capacitance
The amplitude result of relationship.Wherein, the accuracy that digital demodulation is conducive to improve demodulation result is carried out using digital demodulator 133.
The DDS sinusoidal signal generators 111 that the CPU140 is used to control the signal generating module module 110 generate number
Word sinusoidal excitation signal；Work for the programmable amplifier 131 for controlling signal acquisition process module 130；It is described for obtaining
The amplitude for the relationship proportional to measured capacitance that digital demodulator 133 obtains after demodulating is as a result, and be sent to the communication module
150, the communication module 150 exports the amplitude result of the relationship proportional to measured capacitance of acquisition to control system or number
According to the system of reception with analyzing processing, corresponding capacitance is obtained.Wherein, programmable amplifier 131 is a kind of amplification factor by program
The amplifier of control is, it can be achieved that automatically control gain or automatic range switching, and in the present embodiment, the CPU140 is program-controlled puts
The control module of big device 131, the programmable amplifier 131 are discrete control gain amplifier, are used for different measurement ranges
AC measurment voltage signal carry out gain control, reach the job requirement of analog-digital converter 132.
In the present embodiment, the signal generating module 110 further includes a low-pass filter 113, the low-pass filter
113 are connected between digital analog converter 112 and capacitance/voltage transformation module 120, for being converted to the digital analog converter 112
The analog sine pumping signal of acquisition is filtered, and decay unwanted sampling component and spurious signal, and smooth simulation is just
String pumping signal.The output end of the DDS sinusoidal signal generators 111 is sequentially connected in series digital analog converter 112, low-pass filter
113, capacitance/voltage transformation module 120, programmable amplifier 131, analog-digital converter 132, digital demodulator 133 and CPU140, institute
The other end signal input port connection DDS sinusoidal signal generators 111 of digital demodulator 133 are stated, the CPU140 also distinguishes
It is connected with DDS sinusoidal signal generators 111, programmable amplifier 131 and communication module 150.
In this embodiment, it is preferred that second-order low-pass filter of the low-pass filter 113 using Sallen-Key structures
Device, cutoff frequency 600KHz.The capacitance/voltage transformation module 120 is obtaining the filtered simulation of low-pass filter 113 just
String pumping signal, and transform it into AC measurment voltage signal.In certain embodiments, the capacitance/voltage transformation module
120 can obtain the analog sine pumping signal that the conversion of digital analog converter 112 obtains, and transform it into AC measurment voltage letter
Number.
In the present embodiment, the DDS sinusoidal signal generators 111, CPU140, digital demodulator 133 and communication module
150 are realized by FPGA, the advantages of making full use of FPGA parallel computations so that the operation of each module can be carried out at the same time, and be realized
The real-time detection of capacitance signal.The digital analog converter 112 is the DAC chip with 65MHz sample rates and 14 bit resolutions, institute
It is the ADC chips with 65MHz sample rates and 14 bit resolutions to state analog-digital converter 132.
With reference to Fig. 2, in the present embodiment, the capacitance/voltage transformation module 120 includes a capacitance sensor CxAnd with
Capacitance sensor CxDetecting electrode connection for by the capacitance sensor CxThe capacitance of detection is converted to the conversion electricity of voltage
Road 121, the conversion circuit 121 include an operational amplifier U1, a feedback capacity CfAn and feedback resistance Rf.The capacitance passes
Sensor CxSide detecting electrode be connected to the inverting input of the operational amplifier U1, capacitance sensor CxThe other side
Input terminal IN of the detecting electrode as the capacitance/voltage transformation module 120, the output end of the conversion circuit 121 is as electricity
The output end OUT of appearance/voltage transformation module 120, the positive input end grounding of the operational amplifier U1, output end, which is used as, to be turned
Change the output end of circuit 121, the feedback resistance RfWith feedback capacity CfThe output end phase of one end and operational amplifier U1 after parallel connection
Even, the other end is connected with the inverting input of operational amplifier U1.The capacitance sensor CxTwo detecting electrodes connect respectively
It is connected to the capacitance C for holding ground connection one by ones1、Cs2, wherein the capacitance Cs1、Cs2It indicates by connection capacitance sensor CxDetecting electrode
The stray capacitance that introduces of shielded cable, the size of stray capacitance is related with the length of shielded cable, it is considered that the electricity of 1m long
The stray capacitance that cable tie is come is 100pF.Capacitance Cs1For the first stray capacitance, capacitance Cs2For the second stray capacitance, due to first miscellaneous
Spurious capacitance Cs1One end dead earth, another termination analog sine pumping signal, and analog sine pumping signal be alternating current
Press signal, therefore the first stray capacitance Cs1Not will produce can flow through capacitance sensor CxElectric current, to not influencing capacitance sensing
Device CxMeasurement, and the second stray capacitance Cs2One end dead earth, the anti-phase input of another termination operational amplifier U1
End, flows through capacitance sensor CxElectric current may not flow into the second stray capacitance Cs2, to not influence to capacitance sensor CxSurvey
Amount.Therefore, the capacitance/voltage transformation module 120 has the function of anti-stray capacitance, can effectively avoid stray capacitance to capacitance
The influence of measurement accuracy improves the stability and reliability of micro capacitance system 10 of the present invention.
With reference to Fig. 3, the present invention also provides a kind of micro capacitance method, which can be based on upper
State the progress of micro capacitance system comprising following steps：
Step S1, CPU control signal generating module generation pumping signal.
Specifically, the step S1 includes the following steps：
Step S11, CPU control DDS sinusoidal signal generators generation digital sine pumping signal.
The data sinusoidal excitation signal is converted to analog sine pumping signal by step S12, digital analog converter.
The reference signal frequency of the DDS sinusoidal signal generators is fc, output signal frequency fo, the reference signal
Frequency fcWith output signal frequency foRatio beRatio n is an integer, using ratio n as data length, is established
One simple sinusoidal data look-up table, data content are respectively the n with same phase interval in each sinusoidal signal period
The amplitude of a sinusoidal signal, according still further to the reference signal frequency fcBe output to one by one the analog-digital converter can be obtained it is required
Digital sine pumping signal.The resolution ratio of the digital analog converter is L, and the required sinusoidal data being stored in look-up table can
It is calculated according to following two steps：
Phase increment Δ θ：
Wherein, n is the reference signal frequency fcWith output signal frequency foRatio.
A sinusoidal data Data (i) with L bit resolutions of i-th (0≤i≤n)：
Data (i)=Round [2L-1·sin(i·Δθ)+2L-1] (2)
Wherein, Round accords with for rounding operation, in conjunction with formula (1) and (2) it is found that in the sinusoidal data Data (i), the 0th
A data and nth data are all 0, in continuous sinusoidal generating process, the nth data and current period in previous period
The 0th data overlap just, therefore, the two need to only be stayed first, to which multiple sine wave periods are by seamless connection, and each
The number and value of sample point data in period are all identical, and therefore, the DDS sinusoidal signal generators can generate amplitude and frequency
Stable digital sine pumping signal.Preferably, the resolution ratio of the digital analog converter is 14, then L=14.
Step S13, low-pass filter are filtered the analog sine pumping signal, and by filtered simulation
Sinusoidal excitation signal is transmitted to the capacitance/voltage transformation module.
Step S2, capacitance/voltage transformation module receive the pumping signal that the signal generating module provides, according to receiving
Pumping signal obtain AC measurment voltage signal.Wherein, in the present embodiment, the excitation letter that the signal generating module generates
Number be the filtered analog sine pumping signal of low-pass filter.
Specifically, the circuit diagram in conjunction with shown in Fig. 2, analog sine pumping signal caused by signal generating module, that is, defeated
Enter signal Vi(t) be applied on the input terminal of capacitance/voltage transformation module, flow through capacitance sensor electric current be equal to flow through feedback
The sum of the electric current of resistance and feedback capacity, i.e.,：
Wherein, ω is the angular frequency of analog sine pumping signal, CfFor the capacitance of feedback capacity, RfFor feedback resistance
Resistance value, CxFor the capacitance for the measured capacitance that capacitance sensor measures, Vo(t) output signal is indicated.
Arrangement can obtain, AC measurment voltage signal, that is, output signal V that capacitance/voltage transformation module conversion obtainso(t)
For：
Wherein, capacitance/voltage transformation module is not influenced by stray capacitance, has stronger anti-stray capacitance ability, when |
jωCfRf+ 1 | when ＞ ＞ 1, formula (4) can be reduced to：
Wherein, VoAnd ViRespectively output signal Vo(t) and input signal Vi(t) amplitude.As it can be seen that output signal and defeated
The frequency for entering signal is unrelated, moreover, in the case where input signal immobilizes, the amplitude of output signal and the electricity of measured capacitance
Proportional relationship between capacitance, i.e., in the case that the analog sine pumping signal caused by signal generating module immobilizes,
Capacitance/proportional between the voltage transformation module conversion amplitude of AC measurment voltage signal obtained and the capacitance of measured capacitance
Relationship.Capacitance is bigger, and amplitude is bigger, the width for the AC measurment voltage signal that the capacitance/voltage transformation module conversion obtains
Value obtains after passing through signal acquisition process module acquisition process, and the amplitude result of acquisition directly reflects capacitance size, to realize
Capacitance measurement.
Step S3, signal acquisition process module acquire the AC measurment voltage letter that the capacitance/voltage transformation module obtains
Number and it is handled, obtain the amplitude result of proportional to measured capacitance relationship.
Specifically, step S3 includes the following steps：
Step S31, CPU control programmable amplifier acquires the AC measurment voltage that the capacitance/voltage transformation module obtains
Signal simultaneously controls programmable amplifier and is suitably scaled to the AC measurment voltage signal.It wherein, can using programmable amplifier
So that the AC measurment voltage signal for finally entering the analog-digital converter has the amplitude range of most suitable acquisition, to make
Collected signal has best signal-to-noise ratio.In the present embodiment, the programmable amplifier amplifies for discrete control gain
Device reaches the work of analog-digital converter for the AC measurment voltage signal of different measurement ranges to be carried out gain control
It is required that.
Step S32, the AC measurment voltage signal after analog-digital converter scales the programmable amplifier are converted into number
Measurement voltage signal.
Step S33, the number that digital demodulator acquisition digital measurement voltage signal and DDS sinusoidal signal generators generate is just
String pumping signal, and multiplying, acquisition and quilt are carried out according to the digital measurement voltage signal and digital sine pumping signal
Survey the amplitude result of the proportional relationship of capacitance.Wherein, it can no longer need to convert digital signals into simulation using digital demodulation mode
Signal is directly carried out according to the information of the digital sine pumping signal of DDS sinusoidal signal generators and digital measurement voltage signal
Digital demodulation, data result is more accurate and reliable, simplifies the complexity of capacitance measurement system.
In conjunction with Fig. 4, in the present embodiment, specifically, step S33 includes the following steps：
Step S331, digital demodulator need number to be used when demodulation every time is arranged according to the accuracy and speed demand of measurement
The sampling number N of word measurement voltage signal samples the digital measurement voltage signal, obtains Sampling Measurement Data.Its
In, the numerical value of the sampling number N and the reference signal frequency f of DDS sinusoidal signal generatorscWith output signal frequency foBetween
Ratio n numerical value it is equal.
Step S332, digital demodulator send out DDS sinusoidal signals within a complete signal period according to sampling number N
The digital sine pumping signal of raw device is sampled, and the same phase and orthogonal reference signal data of digital sine pumping signal are obtained,
And it will be obtained with mutually multiplying is carried out with the Sampling Measurement Data respectively with reference to signal data and orthogonal reference signal data
Corresponding same phase product signal data and Orthogonal Multiplication signal data.
Specifically, it is assumed that the sample frequency of analog-digital converter is fs, the digital measurement voltage signal obtained after analog-to-digital conversion,
The i.e. described Sampling Measurement Data expression formula is：
Wherein, k indicates that the serial number of sampled point in a sampling period, y (k) indicate the value of k-th of sampled point, A1It is number
The amplitude of measurement voltage signal,It indicates that phase, f indicate frequency, for convenience of indicating, enables
Then formula (6) can be reduced to：
Similarly, after being sampled, the digital sine pumping signal of DDS sinusoidal signal generators needed for mediation process it is same
It is with reference to the expression formula of signal data and orthogonal reference signal data mutually：
Wherein, ri(k) it indicates with mutually with reference to signal data, rq(k) orthogonal reference signal data are indicated, it will be with mutually with reference to letter
Number and orthogonal reference signal data carry out multiplying with the Sampling Measurement Data respectively, you can obtain corresponding same phase
Product signal data pi(k) and Orthogonal Multiplication signal data pq(k)：
Step S333, digital demodulator by N number of same phase product signal data in a complete signal period of acquisition into
Row is cumulative, obtain with phase product signal and, N number of Orthogonal Multiplication signal data in a complete signal period of acquisition is carried out
It is cumulative, obtain Orthogonal Multiplication signal and.
Specifically, cumulative summation is carried out to the same phase product signal data in a complete signal period, it is complete to one
Orthogonal Multiplication signal data in signal period carries out cumulative summation, using digital sine pumping signal in integer complete signal
Integral is 0 characteristic in period, eliminates two frequency multiplication AC compounents, and the sample frequency of analog-digital converter is higher, each complete
There are enough sampling numbers in signal period, then have
Wherein, N is the total number of sampled point in a complete signal period, therefore, by cumulative summation complete cycle, with multiplication
Product signal and Pi(k) and Orthogonal Multiplication signal and Pq(k) it is respectively：
Step S334, digital demodulator is according to the same phase product signal and and Orthogonal Multiplication signal and obtains and tested electricity
The amplitude result of Rongcheng proportionate relationship.
Specifically, the amplitude A of the amplitude result1With corresponding phaseIt is represented by：
Step S4, CPU obtain the amplitude as a result, and sending it to communication module.
Step S5, communication module export the amplitude result to control system or data receiving system, control system
Or data receiving system carries out analyzing processing to the amplitude result received, obtains corresponding capacitance, realizes to capacitance
It measures.
In conclusion micro capacitance system of the present invention is swashed by the way that DDS sinusoidal signal generators are arranged with generating number
Signal is encouraged, the problem of capacitance detecting avoids charge injection and null offset is carried out using digital stimulus signal, reduces capacitance and survey
The capacitance that capacitance sensor measures is converted to AC measurment voltage signal, institute by the deviation of amount using capacitance/voltage transformation module
Stating capacitance/voltage transformation module has the function of anti-stray capacitance, can effectively avoid shadow of the stray capacitance to capacitance measurement precision
It rings, improves the stability and reliability of capacitance measurement system, AC measurment voltage signal is zoomed in and out by programmable amplifier
Analog-to-digital conversion is carried out by by analog-digital converter, so that collected signal has best signal-to-noise ratio, using digital demodulator
Multiplying and demodulation process are carried out to collected signal, obtain the amplitude of relationship proportional to measured capacitance as a result, thus
The measurement for realizing capacitance is conducive to improve the accuracy of capacitance measurement using digital demodulation；The DDS sinusoidal signal generators,
The advantages of CPU, digital demodulator and communication module are realized by FPGA, make full use of FPGA parallel computations so that each module
Calculating can be carried out at the same time, and realize the real-time detection of capacitance signal, and performance is stablized.Micro capacitance method of the present invention utilizes
Digital stimulus signal and digital demodulation avoid the problem that charge injection and null offset, reduce the deviation of capacitance measurement, improve electricity
Hold the accuracy measured, and the acquisition for solving adjusting data is simple and quick.
The foregoing is merely the preferred embodiment of the present invention, rather than do limitation in any form to the present invention.This field
Technical staff can impose various equivalent changes and improvement, all institutes within the scope of the claims on the basis of the above embodiments
The equivalent variations done or modification should all be fallen under the scope of the present invention.
Claims (10)
1. a kind of micro capacitance system, for connecting control system or data receiving system, which is characterized in that described micro-
Low capacitance measurement system includes：
One signal generating module, for generating pumping signal comprising DDS sinusoidal signal generators and digital analog converter, it is described
DDS sinusoidal signal generators are used for for generating digital sine pumping signal, the digital analog converter by the DDS sinusoidal signals
The digital sine pumping signal that generator generates is converted to analog sine pumping signal；
One capacitance/voltage transformation module, the pumping signal for generating the signal generating module are transformed to AC measurment electricity
Press signal；
One signal acquisition process module, the AC measurment voltage letter obtained for acquiring the capacitance/voltage transformation module conversion
Number and it is handled comprising programmable amplifier, analog-digital converter and digital demodulator, the programmable amplifier for pair
The AC measurment voltage signal zooms in and out, and the exchange after the analog-digital converter is used to scale the programmable amplifier is surveyed
Amount voltage signal is converted into digital measurement voltage signal, the digital demodulator be used for according to the digital measurement voltage signal and
The digital sine pumping signal that DDS sinusoidal signal generators generate is demodulated, and the width of relationship proportional to measured capacitance is obtained
It is worth result；
One CPU generates pumping signal for controlling signal generating module；Programming amplifying for controlling signal acquisition process module
The work of device；Amplitude knot for obtaining and sending the relationship proportional to measured capacitance obtained after the digital demodulator demodulation
Fruit；
One communication module, amplitude result and output for obtaining relationship proportional to measured capacitance to the control system or
Data receiving system.
2. micro capacitance system as described in claim 1, it is characterised in that：The capacitance/voltage transformation module includes
The capacitance for detecting the capacitance sensor for having a capacitance sensor and being connect with the detecting electrode of capacitance sensor turns
It is changed to the conversion circuit of voltage, the conversion circuit includes an operational amplifier, a feedback capacity and a feedback resistance, the electricity
The detecting electrode for holding sensor is connected to the inverting input of the operational amplifier, the normal phase input end of the operational amplifier
It is grounded, output end of the output end as conversion circuit, one end and operation amplifier after the feedback resistance and feedback capacity parallel connection
The output end of device is connected, and the other end is connected with the inverting input of operational amplifier.
3. micro capacitance system as described in claim 1, it is characterised in that：The digital analog converter is with 65MHz
The DAC chip of sample rate and 14 bit resolutions, the analog-digital converter are the ADC with 65MHz sample rates and 14 bit resolutions
Chip.
4. micro capacitance system as described in claim 1, it is characterised in that：The signal generating module further includes one low
Bandpass filter, the analog sine pumping signal for being obtained to digital analog converter conversion are filtered.
5. micro capacitance system as claimed in claim 4, it is characterised in that：The low-pass filter is Sallen-Key
The second-order low-pass filter of structure, cutoff frequency 600KHz.
6. micro capacitance system as described in claim 1, it is characterised in that：The DDS sinusoidal signal generators, CPU,
Digital demodulator and communication module are realized by FPGA.
7. a kind of micro capacitance method, which is characterized in that the micro capacitance method includes the following steps：
CPU controls signal generating module and generates pumping signal；
Capacitance/voltage transformation module receives the pumping signal that the signal generating module provides, according to the pumping signal received
Obtain AC measurment voltage signal；
Signal acquisition process module acquires the AC measurment voltage signal that the capacitance/voltage transformation module obtains and is carried out to it
Processing obtains the amplitude result of relationship proportional to measured capacitance；
CPU obtains the amplitude as a result, and sending it to communication module；
Communication module exports the amplitude result to control system or data receiving system.
8. micro capacitance method as claimed in claim 7, which is characterized in that the CPU controls signal generating module production
Raw pumping signal includes the following steps：
CPU controls DDS sinusoidal signal generators and generates digital sine pumping signal；
The digital sine pumping signal is converted to analog sine pumping signal by digital analog converter；
Low-pass filter is filtered the analog sine pumping signal.
9. micro capacitance method as claimed in claim 7, which is characterized in that the signal acquisition process module acquires institute
It states the AC measurment voltage signal that capacitance/voltage transformation module obtains and it is handled, obtain proportional to measured capacitance
The amplitude result of relationship includes the following steps：
CPU control programmable amplifiers acquire the AC measurment voltage signal that the capacitance/voltage transformation module obtains, to the friendship
Flow measurement voltage signal zooms in and out；
AC measurment voltage signal after analog-digital converter scales the programmable amplifier is converted into digital measurement voltage signal；
Digital demodulator obtains the digital sine excitation letter that the digital measurement voltage signal and DDS sinusoidal signal generators generate
Number, and multiplying is carried out according to the digital measurement voltage signal and digital sine pumping signal, obtain with measured capacitance at
The amplitude result of proportionate relationship.
10. micro capacitance method as claimed in claim 9, which is characterized in that the digital demodulator obtains the number
The digital sine pumping signal that word measurement voltage signal and DDS sinusoidal signal generators generate, and according to digital measurement electricity
Press signal and digital sine pumping signal to carry out multiplying, the amplitude result for obtaining relationship proportional to measured capacitance include with
Lower step：
Digital demodulator needs digital voltage to be used to measure letter when demodulation every time is arranged according to the accuracy and speed demand of measurement
Number sampling number N, the digital measurement voltage signal is sampled, obtain Sampling Measurement Data；
Digital demodulator generates DDS sinusoidal signal generators within a complete signal period according to the sampling number N
Digital sine pumping signal is sampled, and obtains its with mutually and orthogonal reference signal data, and by the same phase reference signal number
According to and orthogonal reference signal data carry out multiplying with Sampling Measurement Data respectively, obtain corresponding same phase product signal data
And Orthogonal Multiplication signal data；
Digital demodulator adds up N number of same phase product signal data in a complete signal period of acquisition, obtains same
Phase product signal and, N number of Orthogonal Multiplication signal data in a complete signal period of acquisition is added up, obtain it is orthogonal
Product signal and；
Digital demodulator is according to the same phase product signal and and Orthogonal Multiplication signal and obtains proportional to measured capacitance relationship
Amplitude result.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109917185A (en) * | 2019-03-28 | 2019-06-21 | 北京同创微纳科技有限公司 | A kind of capacitance sensor and its working method and application based on resonance frequency measurement |
| CN111307180A (en) * | 2020-04-14 | 2020-06-19 | 国网河南省电力公司信息通信公司 | Method for reducing power supply noise of optical balance receiver for optical cable detection |
| CN112666400A (en) * | 2020-11-18 | 2021-04-16 | 西安交通大学 | Capacitance measuring circuit capable of automatically compensating parasitic capacitance and use method and application thereof |
| CN113219257A (en) * | 2021-04-29 | 2021-08-06 | 深圳市东昕科技有限公司 | Parameter measuring circuit of capacitor and ESR capacity measuring instrument of capacitor |
| CN114137043A (en) * | 2021-12-31 | 2022-03-04 | 东北林业大学 | Living standing wood sapwood water content measuring instrument based on weak capacitance detection method |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1828315A (en) * | 2006-01-24 | 2006-09-06 | 东北大学 | High voltage alternate driver circuit for determining micro capacitance |
| CN102012464A (en) * | 2010-09-30 | 2011-04-13 | 彭建学 | Micro capacitance measurement method and special device |
| CN103675460A (en) * | 2013-01-08 | 2014-03-26 | 浙江大学 | Measurement device of capacitive coupling type non-contact conductance based on phase-sensitive demodulation and method thereof |
| CN104597328A (en) * | 2015-01-12 | 2015-05-06 | 东南大学 | Electrostatic interference preventing capacitance measuring circuit and method |
| CN106154048A (en) * | 2016-08-12 | 2016-11-23 | 浙江大学 | The anti-measurement apparatus of contactless fluid resistance based on digital phase-sensitive solution mediation virtual inductor technology and method |
| CN106771642A (en) * | 2015-11-19 | 2017-05-31 | 许亚夫 | A kind of capacitance measurement circuit for capacitance tomography system |
-
2018
- 2018-02-09 CN CN201810136512.9A patent/CN108333437A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1828315A (en) * | 2006-01-24 | 2006-09-06 | 东北大学 | High voltage alternate driver circuit for determining micro capacitance |
| CN102012464A (en) * | 2010-09-30 | 2011-04-13 | 彭建学 | Micro capacitance measurement method and special device |
| CN103675460A (en) * | 2013-01-08 | 2014-03-26 | 浙江大学 | Measurement device of capacitive coupling type non-contact conductance based on phase-sensitive demodulation and method thereof |
| CN104597328A (en) * | 2015-01-12 | 2015-05-06 | 东南大学 | Electrostatic interference preventing capacitance measuring circuit and method |
| CN106771642A (en) * | 2015-11-19 | 2017-05-31 | 许亚夫 | A kind of capacitance measurement circuit for capacitance tomography system |
| CN106154048A (en) * | 2016-08-12 | 2016-11-23 | 浙江大学 | The anti-measurement apparatus of contactless fluid resistance based on digital phase-sensitive solution mediation virtual inductor technology and method |
Non-Patent Citations (1)
| Title |
|---|
| 张少谦等: "一种基于DDS与单片机的自动电容测量系统设计", 《科学技术与工程》 * |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109917185A (en) * | 2019-03-28 | 2019-06-21 | 北京同创微纳科技有限公司 | A kind of capacitance sensor and its working method and application based on resonance frequency measurement |
| CN109917185B (en) * | 2019-03-28 | 2021-01-15 | 北京同创微纳科技有限公司 | Capacitive sensor based on resonant frequency measurement and working method and application thereof |
| CN111307180A (en) * | 2020-04-14 | 2020-06-19 | 国网河南省电力公司信息通信公司 | Method for reducing power supply noise of optical balance receiver for optical cable detection |
| CN111307180B (en) * | 2020-04-14 | 2021-10-15 | 国网河南省电力公司信息通信公司 | Method for reducing power supply noise of optical balance receiver for optical cable detection |
| CN112666400A (en) * | 2020-11-18 | 2021-04-16 | 西安交通大学 | Capacitance measuring circuit capable of automatically compensating parasitic capacitance and use method and application thereof |
| CN112666400B (en) * | 2020-11-18 | 2023-06-30 | 西安交通大学 | Capacitance measuring circuit capable of automatically compensating parasitic capacitance, and use method and application thereof |
| CN113219257A (en) * | 2021-04-29 | 2021-08-06 | 深圳市东昕科技有限公司 | Parameter measuring circuit of capacitor and ESR capacity measuring instrument of capacitor |
| CN114137043A (en) * | 2021-12-31 | 2022-03-04 | 东北林业大学 | Living standing wood sapwood water content measuring instrument based on weak capacitance detection method |
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