CN105067654A - Single-mode resonant cavity sensor-based solution concentration measurement method - Google Patents
Single-mode resonant cavity sensor-based solution concentration measurement method Download PDFInfo
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- CN105067654A CN105067654A CN201510579411.5A CN201510579411A CN105067654A CN 105067654 A CN105067654 A CN 105067654A CN 201510579411 A CN201510579411 A CN 201510579411A CN 105067654 A CN105067654 A CN 105067654A
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Abstract
The invention relates to a single-mode resonant cavity sensor-based solution concentration measurement method. The method comprises the following steps: adding a solution with a certain concentration into a resonant cavity, inputting a wave guide signal into the resonant cavity, and enabling a resonant cavity reflection signal to enter an amplitude measurement circuit and a phase measurement circuit through a circulator; performing precise rectifying and filtering on the reflection signal to obtain a reflection direct-current voltage signal, comparing the reflection direct-current voltage signal with a reference voltage to acquire a signal indicating whether the resonant cavity is in a resonant state; acquiring the signal indicating whether the carrier modulation signal frequency is greater than the resonant frequency of the resonant cavity according to the wave guide signal and the resonant cavity reflection signal which is output from the resonant cavity, and inputting the two detecting results into an FPGA (Field Programmable Gate Array); when the FPGA receives the signal indicating that the resonant cavity is subject to resonance, controlling a VCO (Voltage Controlled Oscillator) to output the resonant frequency, and simultaneously reading the resonant frequency and the frequency information of a local oscillator into a frequency mixer to calculate a frequency offset. Different frequency offsets are obtained for the solutions with different concentrations. According to the method, more precise measurement precision can be obtained; the measurement cost is lower.
Description
Art
The invention belongs to Microwave Measurement Technique field, relate to a kind of solution concentration measuring method.
Background technology
Concentration is the important physical parameter characterizing dielectric property, realize the on-line measurement of strength of fluid, play an important role in each fields such as chemical industry, food, medicine, build the on-line measurement system that measurement range is wide, measuring accuracy is high and greatly simplify material, solution medium characteristic test related experiment and operation, need sensor accurately to measure the concentration of solution to be measured in such as chemical experiment, or in the industry the concentration of solution is detected etc.
Single-mode Resonator is as a kind of sensor based on microwave technology, there is high sensitivity and the high advantage of Measurement sensibility, the on-line measurement for measured object concentration can be realized, current scientific research field measures based on Single-mode Resonator the direct measurement that document (as [1]-[the 5]) research method of concentration concentrates on resonator cavity S parameter, namely the S parameter of resonator cavity is directly measured with network analyzer, concentration information is converted into calibration curve information, and sets up Relational database.
But the method being core with direct measurement parameter have two significantly not enough: one is that data reflection is directly perceived, and calibration curve information is intensive and precision is not high enough among a small circle, is not easy accurately to be reflected at calibration curve information when concentration change is small; Two is that each measurement all will adopt the high precision apparatus such as network analyzer, and cost is higher.
The sensor that Single-mode Resonator is measured as solution, has higher measurement sensistivity.Based on microwave perturbation theory, the Medium perturbation that after adding fluid to be measured, concentration change produces, make intra resonant cavity electromagnetic field generation perturbation, thus affect the state of resonance, resonance frequency can change.The application for a patent for invention 201210009379.3 of submitting before applicant gives a kind of microwave resonant cavity sensor for measuring solution concentration and measuring system.
Summary of the invention
The object of the invention is, on the basis of the sensor researched and developed before and measuring system, to provide a kind of solution concentration measuring method based on singlemode resonance cavity sensor.Measuring method of the present invention, concentration information is converted into the side-play amount of resonance frequency, and non-immediate survey sensor correlation parameter, utilize the solution concentration and frequency offset database one to one set up in advance, can be implemented in line to measure, obtain comparatively accurate measuring accuracy, measure cost also less.Technical scheme of the present invention is as follows:
Based on a solution concentration measuring method for singlemode resonance cavity sensor, comprising:
Add certain density solution in resonator cavity, by waveguide signal input resonator, resonator cavity reflected signal enters amplitude measurement circuitry by circulator and whether phase measuring circuit detection resonator cavity resonance occurs.
In amplitude measurement circuitry, reflected signal obtains reflected DC voltage signal by precision rectifying and filtering; Resonator cavity reflected DC voltage signal is under resonance condition less than predetermined threshold value, and by comparing with the reference voltage of the amplitude measurement circuitry determined according to threshold value, if reflected DC voltage signal is less than reference voltage, resonator cavity is in resonant condition; Otherwise resonator cavity is in non-resonant condition, the resonant condition signal of the resonator cavity that amplitude measurement circuitry detects is input to FPGA; If do not have resonance, FPGA controls resonator cavity reflected signal and is transferred to phase measuring circuit, with controlling and adjustment frequency under the state of non-resonance;
In phase measuring circuit, being incorporated to multiplier by waveguide signal with from the resonator cavity reflected signal that resonator cavity exports, by drawing direct current signal after low-pass filter, if two signal phases are identical, showing that carrier (boc) modulated signals frequency is greater than resonant frequency; Phase place is contrary, and show that carrier (boc) modulated signals frequency is less than resonant frequency, the testing result of phase measuring circuit outputs to FPGA;
FPGA outputs signal voltage controlled oscillator VCO, and the signal that voltage controlled oscillator exports, through directional coupler process, is divided into two parts: a part, through circulator, is selected to be input in microwave cavity by circulator, provides external energy to produce vibration; Another part is then input to frequency mixer as original signal, survey frequency change and frequency change;
Four kinds of signal messages that FPGA receives are: 1, when receiving the signal of resonator cavity generation resonance, control VCO export resonance frequency, and and the frequency information of local oscillator read in frequency mixer simultaneously and calculate frequency-splitting, be frequency shift (FS); 2, when receiving resonator cavity and the signal of resonance not occurring, control resonator cavity reflected signal and enter phase measuring circuit; 3, when receiving carrier (boc) modulated signals frequency and being greater than the signal of resonant frequency, control VCO reduces frequency information, and is input to resonator cavity by circulator and returns detection; 4, when receiving carrier (boc) modulated signals frequency and being less than the signal of resonant frequency, control VCO increases frequency information, and is input to resonator cavity by circulator and returns detection;
Different frequency offsets is obtained to the solution of different concentration, sets up the relational database of frequency shift (FS) and concentration accordingly, thus realize measurement of concetration.
The solution concentration measuring method based on singlemode resonance cavity sensor of this, has following advantage and good effect:
1, control and arithmetic system are based on fpga chip, and computing velocity is fast, and Measuring Time was at 1 to 2 seconds, and this research is directly measured without network analyzer, therefore greatly reduced costs, and the storage form of information is frequency values.
2, different frequency difference and concentration value store and generate database, and frequency searches related data as digital signal is more convenient than curve signal.Concentration measurement system Measurement Resolution is high, method provided by the invention is utilized to be 298.15K in temperature, be that two kinds of sugar aqueous solution glucose, fructose solns of 1g/L-20g/L are tested with concentration, the resolution of measurement of concetration reaches 10mg/dL, higher than measuring method precision such as chemical analysis.
Accompanying drawing explanation
Fig. 1 concentration measurement system block diagram
Fig. 2 concentration measurement system Software for Design process flow diagram
The database (solution concentration is 1g/L-20g/L) of Fig. 3 frequency change and concentration
Specific implementation method
The method that the present invention proposes is the further achievement in research on the basis of the microwave resonant cavity sensor and measuring system of measuring solution concentration provided in patented claim 201210009379.3.
As Fig. 1, fpga chip is based on the method for software and hardware combining, and software language controls, calls each several part, hardware cell survey frequency numerical value.Circulator and wave detector processing signals are the accessible signal of low frequency, the voltage changing digital-to-analog circuit can control the output frequency of voltage controlled oscillator, input one end of frequency mixer is the signal before adding solution, and one end is the signal after adding solution, exports the difference into resonance frequency.
Process flow diagram in Fig. 2 is controlled by C language, and arithmetic section is realized by Verilog language, and loop program finds new resonance frequency, just circulates if be in non-resonant condition always, until new resonant condition reaches.When adding certain density solution in resonator cavity, waveguide signal input resonator, resonator cavity reflected signal enters amplitude measurement circuitry by circulator and whether phase measuring circuit detection resonator cavity resonance occurs.
Amplitude measurement circuitry comprises low-pass filter, amplifier and comparer, arranges reference voltage and judges amplitude, output signal be less than reference voltage then current state be resonant condition, output signal be greater than reference voltage then current state be non-resonant condition.
In amplitude measurement circuitry, reflected signal obtains d. c. voltage signal by precision rectifying and filtering.Resonator cavity reflected DC signal is under resonance condition less than 200mV, is compared by the reference voltage (200mV) of amplitude measurement circuitry, exports 2 binary signal 0,1 to FPGA processor.If resonator cavity output voltage is less than the reference voltage of 200mV, resonator cavity is in resonant condition, and output port exports 0 to FPGA; Otherwise resonator cavity is in non-resonant condition, output port exports 1 to FPGA.If there is no resonance, control resonator cavity Signal transmissions to phase measuring circuit, with controlling and adjustment frequency under the state of non-resonance.
Phase measuring circuit comprises multiplier, low-pass filter and comparer, and after multiplier process after filtering, the output signal of plus or minus represents homophase or anti-phase.Signal frequency through microwave cavity is greater than resonance frequency then homophase, and comparator reference voltage is set to zero, exports " 1 " and represents that ongoing frequency is greater than resonance frequency, export " 0 " and then represent that ongoing frequency is less than resonance frequency.
In phase measuring circuit, will the modulation signal (being waveguide signal) of resonator cavity be input to and be incorporated to multiplier, by drawing direct current signal after low-pass filter from the reflection restituted signal that resonator cavity exports.If two signal phases are identical, export the voltage signal being greater than 0, the voltage signal that phase reinfusion is less than 0.By numeric door, voltage signal is converted into 2 binary signal of 0,1.Namely reflect restituted signal identical with resonator cavity modulating signal phase, show that carrier (boc) modulated signals frequency is greater than resonant frequency, export 1 to FPGA; Phase place is contrary, shows that carrier (boc) modulated signals frequency is less than resonant frequency, exports 0 to FPGA.
For four kinds of signal messages that FPGA can receive, be discussed below respectively: 0 signal 1, receiving amplitude measurement circuitry, resonator cavity generation resonance is described, control VCO export resonance frequency, read in frequency mixer with the frequency information of local oscillator simultaneously and calculate frequency-splitting, be frequency shift (FS).2, receive 1 signal of amplitude measurement circuitry, illustrate that resonance does not occur resonator cavity, control resonator cavity reflected signal and enter phase measuring circuit.3, receive 1 signal of amplitude measurement circuitry, illustrate that carrier (boc) modulated signals frequency is greater than resonant frequency, control VCO reduces frequency information, and is input to resonator cavity by circulator and returns detection; 4, receive 0 signal of amplitude measurement circuitry, illustrate that carrier (boc) modulated signals frequency is less than resonant frequency, control VCO increases frequency information, and is input to resonator cavity by circulator and returns detection;
FPGA outputs signal voltage controlled oscillator (VCO), the signal that voltage controlled oscillator exports is through directional coupler process, be divided into two parts: a part, through circulator, is selected to be input in microwave cavity by circulator, provides external energy to produce vibration; Another part is then input to frequency mixer as original signal, survey frequency change and frequency change.
Measurement module is passed through from the resonance frequency shift signal of mixed rate-adaptive pacemaker, the frequency offset measured can be read in FPGA, to different frequency offsets be obtained to the solution of different concentration, by being stored in the information in FPGA, finally setting up the relational database of frequency shift (FS) and concentration.
As shown in Figure 3, carry out emulation testing for glucose, fructose two kinds of solution, along with solution concentration increases, the skew of resonance frequency increases simultaneously, obtains the linear relationship of concentration and resonance frequency shift.By matching, obtain the linear relationship of frequency shift (FS) and glucose concentration and fructose soln concentration.As follows:
Δf
1＝2.1528×10
6·C
1
Δf
2＝2.1445×10
6·C
2
Wherein, C
1, C
2be respectively glucose and fructose soln concentration, Δ f
1with Δ f
2for respective frequencies skew.
Claims (2)
1., based on a solution concentration measuring method for singlemode resonance cavity sensor, comprising:
Add certain density solution in resonator cavity, by waveguide signal input resonator, resonator cavity reflected signal enters amplitude measurement circuitry by circulator and whether phase measuring circuit detection resonator cavity resonance occurs.
In amplitude measurement circuitry, reflected signal obtains reflected DC voltage signal by precision rectifying and filtering; Resonator cavity reflected DC voltage signal is under resonance condition less than predetermined threshold value, and by comparing with the reference voltage of the amplitude measurement circuitry determined according to threshold value, if reflected DC voltage signal is less than reference voltage, resonator cavity is in resonant condition; Otherwise resonator cavity is in non-resonant condition, the resonant condition signal of the resonator cavity that amplitude measurement circuitry detects is input to FPGA; If do not have resonance, FPGA controls resonator cavity reflected signal and is transferred to phase measuring circuit, with controlling and adjustment frequency under the state of non-resonance;
In phase measuring circuit, being incorporated to multiplier by waveguide signal with from the resonator cavity reflected signal that resonator cavity exports, by drawing direct current signal after low-pass filter, if two signal phases are identical, showing that carrier (boc) modulated signals frequency is greater than resonant frequency; Phase place is contrary, and show that carrier (boc) modulated signals frequency is less than resonant frequency, the testing result of phase measuring circuit outputs to FPGA;
FPGA outputs signal voltage controlled oscillator VCO, and the signal that voltage controlled oscillator exports, through directional coupler process, is divided into two parts: a part, through circulator, is selected to be input in microwave cavity by circulator, provides external energy to produce vibration; Another part is then input to frequency mixer as original signal, survey frequency change and frequency change;
Four kinds of signal messages that FPGA receives are: 1, when receiving the signal of resonator cavity generation resonance, control VCO export resonance frequency, and and the frequency information of local oscillator read in frequency mixer simultaneously and calculate frequency-splitting, be frequency shift (FS); 2, when receiving resonator cavity and the signal of resonance not occurring, control resonator cavity reflected signal and enter phase measuring circuit; 3, when receiving carrier (boc) modulated signals frequency and being greater than the signal of resonant frequency, control VCO reduces frequency information, and is input to resonator cavity by circulator and returns detection; 4, when receiving carrier (boc) modulated signals frequency and being less than the signal of resonant frequency, control VCO increases frequency information, and is input to resonator cavity by circulator and returns detection;
Different frequency offsets is obtained to the solution of different concentration, sets up the relational database of frequency shift (FS) and concentration accordingly, thus realize measurement of concetration.
2. measuring method according to claim 1, is characterized in that, described threshold value is 200mV.
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Cited By (7)
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| CN105866158A (en) * | 2016-03-31 | 2016-08-17 | 武汉大学 | Resonant magnetic coupling-based nondestructive solution concentration detection device and detection method |
| CN107356613A (en) * | 2017-08-28 | 2017-11-17 | 天津大学 | A kind of microwave resonant cavity sensor measurement of blood sugar concentration method |
| CN107655902A (en) * | 2017-08-25 | 2018-02-02 | 天津大学 | A kind of circular microwave resonant cavity sensor solution concentration measuring method |
| CN107782747A (en) * | 2017-11-16 | 2018-03-09 | 天津大学 | A kind of microwave resonator blood alcohol concentration measuring method |
| CN109931921A (en) * | 2017-12-15 | 2019-06-25 | 西安邮电大学 | It is a kind of to automatically track shake control system and implementation method for laser gyro |
| CN113358708A (en) * | 2021-06-07 | 2021-09-07 | 苏州大学 | Non-contact measuring device and method for solution concentration |
| CN115220370A (en) * | 2021-04-16 | 2022-10-21 | 天津大学 | FPGA-based solution concentration real-time monitoring system |
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107655902A (en) * | 2017-08-25 | 2018-02-02 | 天津大学 | A kind of circular microwave resonant cavity sensor solution concentration measuring method |
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| CN107782747A (en) * | 2017-11-16 | 2018-03-09 | 天津大学 | A kind of microwave resonator blood alcohol concentration measuring method |
| CN109931921A (en) * | 2017-12-15 | 2019-06-25 | 西安邮电大学 | It is a kind of to automatically track shake control system and implementation method for laser gyro |
| CN115220370A (en) * | 2021-04-16 | 2022-10-21 | 天津大学 | FPGA-based solution concentration real-time monitoring system |
| CN113358708A (en) * | 2021-06-07 | 2021-09-07 | 苏州大学 | Non-contact measuring device and method for solution concentration |
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