CN104459313A - Signal collecting device and method of double-resonance-element quartz crystal microbalance (QCM) - Google Patents

Abstract

The invention discloses a signal collecting device and method of a double-resonance-element quartz crystal microbalance (QCM). The signal collecting device of the double-resonance-element QCM comprises a drive signal generator, a QCM sensing unit, a signal processing unit, an A/D converter, a single chip microcomputer system and a PC. The QCM sensing unit comprises a reference QCM and a detection QCM, and the signal processing unit processes the reference QCM and the detection QCM through the correlation principle. The single chip microcomputer system controls the frequency of the drive signal generator, the read and write of the A/D converter and the communication of the single chip microcomputer system and the PC. The single chip microcomputer system writes control words into the drive signal generator, the drive signal generator generates cosine signals with controllable frequencies to drive the reference QCM and the detection QCM of the QCM sensing unit, the two paths of QCM output signals are processed by the signal processing unit through the correlation principle, digital signals are generated through the A/D converter to be sent to the single chip microcomputer system, and the signals are sent to the PC ultimately. By means of the signal collecting device and method of the double-resonance-element QCM, needed amplitude and frequency information can be acquired through one-time measurement, oscillation stop can be avoided when large damping liquid is measured, and the applied range is wider.

Description

The signal pickup assembly of a kind of double resonance unit QCM (Quartz Crystal Microbalance) and method

Technical field

The present invention relates to resonant transducer technical field, particularly the signal pickup assembly of a kind of double resonance unit QCM (Quartz Crystal Microbalance) and method.

Background technology

QCM (Quartz Crystal Microbalance) (Quartz Crystal Microbalance, be called for short QCM) be that upper and lower surface by cutting quartz wafer at AT plates circular gold electrode and the one that forms has high-resolution piezoelectric sensor, during measurement quality, precision can reach nanogram level.

The measuring principle of QCM is based on piezoelectric effect, when the electrode of QCM contacts with test substance, the character (as: quality, viscosity, density etc.) of test substance will change the resonance frequency of QCM, the change of QCM resonance frequency and the character of test substance linear, thus record the character of test substance by the change of resonance frequency.

When measuring solid:

$\mathrm{\Δf}=\frac{-2{f_R}^2\mathrm{\Δm}}{A{\left({\stackrel{\‾}{c}}_{66}{\mathrm{\ρ}}_q\right)}^{1/2}}$

Wherein, it is the piezoelectricity strengthening modulus of shearing (2.93 × 10 of quartz crystal ¹¹dynecm ^-2), ρ _qthe density (2.650gcm of quartz crystal ^-3).With the quartz wafer of diameter 14mm, thickness 0.272mm, electrode radius is the QCM of 3mm is example, its theoretical resonance frequency f _rfor 6.12MHz.Then above formula is:

When measuring solid, Δ f ≈-3 × 10 ⁸Δ m, it can thus be appreciated that when frequency change resolution reaches 1Hz, measuring accuracy just can reach 3.3ng.

As the high-precision survey instrument of one, according to the difference of research material, QCM is progressively used in gas phase, liquid phase.Researchist finds in the research field such as chemistry, biology, medical science with to measuring, QCM requires that higher engineering field has unique advantage and good application prospect.Simultaneously QCM can with other combine with technique, obtain the advantage of both sides, such as combine the electrochemical quartz crystal microbalance (EQCM) developed with electrochemical techniques, be used for the research of the aspect such as solution viscosity effect in electro-deposition, gold electrode burn into depletion layer.The dissipative type QCM (Quartz Crystal Microbalance) (QCM-D) grown up in conjunction with energy dissipation can measure the parameter such as quality, viscosity, modulus of shearing of plane of crystal material especially simultaneously, promotes the development of the research of the aspect such as adsorption and desorb, surface reaction, body sign.

In current existing measurement mechanism, the method of main employing oscillatory circuit, and the defect that the method for oscillatory circuit has it intrinsic: first, the quantity of information measured by the method for oscillatory circuit is little, unique parameters series resonance frequency point can only be measured, and parallel resonance frequency point can not be obtained; Secondly, the method application of oscillatory circuit is little, failure of oscillation can occur in large damping solution.In some QCM fields of measurement, it is desirable that the character of test substance under the true temperature at scene and humidity environment, although can be revised result by modes such as temperature compensations, there is time delay in measurement.

Summary of the invention

The object of the invention is the signal pickup assembly and the method that provide a kind of double resonance unit QCM (Quartz Crystal Microbalance), and to realize the micro-sky of quartz crystal, (signal drives and the extraction of weak useful signal in noise background.

The technical solution realizing the object of the invention is: the signal pickup assembly of a kind of double resonance unit QCM (Quartz Crystal Microbalance), comprise drive signal generator, QCM sensing unit, signal processing unit, A/D converter, Single Chip Microcomputer (SCM) system, PC, wherein drive signal generator, QCM sensing unit, signal processing unit, A/D converter, Single Chip Microcomputer (SCM) system are connected successively, the control end access drive signal generator of Single Chip Microcomputer (SCM) system, the data output end access PC of Single Chip Microcomputer (SCM) system; Described QCM sensing unit comprises with reference to QCM and detects QCM, and signal processing unit adopts correlation principle to reference QCM and detects QCM process;

Described Single Chip Microcomputer (SCM) system controls the communication of the frequency of drive signal generator, the read-write of A/D converter and Single Chip Microcomputer (SCM) system and PC, control word is write to drive signal generator by Single Chip Microcomputer (SCM) system, drive signal generator produces the controlled cosine signal of frequency, this cosine signal drives the reference QCM of QCM sensing unit and detects QCM, two-way QCM outputs signal and adopts after correlation principle process through signal processing unit, generate digital signal through A/D converter again and send to Single Chip Microcomputer (SCM) system, final signal is sent to PC by Single Chip Microcomputer (SCM) system.

A signal acquisition method for double resonance unit QCM (Quartz Crystal Microbalance), comprises the following steps:

Step 1, initialization whole system, comprising the initialization of each detection module and host computer interface;

Step 2, arranges the cycle of Single Chip Microcomputer (SCM) system timer;

Step 3, drive signal generator produces the controlled cosine signal of frequency, and this cosine signal drives the reference QCM of QCM sensing unit and detects QCM and produces two-way QCM output signal;

Step 4, two-way QCM outputs signal and adopts correlation principle to carry out processing the frequency and voltage value obtained with reference to QCM and detection QCM through signal processing unit;

Step 5, gained frequency and voltage value generates digital signal through A/D converter again and sends to PC through Single Chip Microcomputer (SCM) system;

Step 6, repeat step 3 ~ 5, use swept frequency range is f ₁~ f ₂cosine signal QCM sensing unit is driven, obtained all frequency and voltage values are plotted as spectral characteristic curve, determine with reference to QCM according to this curve and detect the resonance frequency of QCM.

Compared with prior art, its remarkable advantage is in the present invention: (1) this device adopts Spectral Analysis Method, analyzes the signal that QCM gathers, and the information that can measure is complete, only needs one-shot measurement just can obtain required amplitude and frequency information; (2) can not failure of oscillation when measuring large damping liquid, the device scope of application is more extensive, and data measured is in calculating and explain and have more simplification; (3) adopt the double resonance meta design with reference to QCM, can well measurement environment be eliminated, as humidity, the error that temperature etc. cause.

Accompanying drawing explanation

Fig. 1 is the structured flowchart of the signal pickup assembly of double resonance of the present invention unit QCM (Quartz Crystal Microbalance).

Fig. 2 is the concrete structure figure of the signal pickup assembly of double resonance of the present invention unit QCM (Quartz Crystal Microbalance).

Fig. 3 is the process flow diagram of the signal acquisition method of double resonance of the present invention unit QCM (Quartz Crystal Microbalance).

Fig. 4 is the interruption process flow diagram of the signal acquisition method of double resonance of the present invention unit QCM (Quartz Crystal Microbalance).

Embodiment

Below in conjunction with drawings and the specific embodiments, the present invention is described in further details.

Order of the present invention provides the signal pickup assembly of a kind of crystal microbalance (QCM), can realize driving and the extraction of weak useful signal in noise background the signal of crystal microbalance.System core control section is Single Chip Microcomputer (SCM) system, and Single Chip Microcomputer (SCM) system is responsible for the frequency control of waveform generator, the read-write of A/D chip and the communication etc. with PC.Control word is write to DDS by single-chip microcomputer, produce the cosine signal that frequency is controlled, the QCM resonator of cosine signal on driving stage drives testing circuit and the QCM resonator on reference circuit, two-way QCM outputs signal after lock-in amplify circuit and filtering circuit process, convert digital signal to and send to Single Chip Microcomputer (SCM) system, Single Chip Microcomputer (SCM) system sends PC to after the signal of acceptance being done necessary process, so far just completes a gatherer process.If scanned according to predetermined frequency step, PC by the signal value on all Frequency points of receiving, and can go out amplitude-frequency and the phase-frequency characteristic curve of QCM by real-time rendering.This is the Structure and Process of whole QCM pick-up unit work.

Composition graphs 1, the signal pickup assembly of double resonance unit of the present invention QCM (Quartz Crystal Microbalance), comprise drive signal generator, QCM sensing unit, signal processing unit, A/D converter, Single Chip Microcomputer (SCM) system, PC, wherein drive signal generator, QCM sensing unit, signal processing unit, A/D converter, Single Chip Microcomputer (SCM) system are connected successively, the control end access drive signal generator of Single Chip Microcomputer (SCM) system, the data output end access PC of Single Chip Microcomputer (SCM) system; Described QCM sensing unit comprises with reference to QCM and detects QCM, and signal processing unit adopts correlation principle to reference QCM and detects QCM process;

Described Single Chip Microcomputer (SCM) system controls the communication of the frequency of drive signal generator, the read-write of A/D converter and Single Chip Microcomputer (SCM) system and PC, control word is write to drive signal generator by Single Chip Microcomputer (SCM) system, drive signal generator produces the controlled cosine signal of frequency, this cosine signal drives the reference QCM of QCM sensing unit and detects QCM, two-way QCM outputs signal and adopts after correlation principle process through signal processing unit, generate digital signal through A/D converter again and send to Single Chip Microcomputer (SCM) system, final signal is sent to PC by Single Chip Microcomputer (SCM) system.

Composition graphs 2, described drive signal generator comprises the Direct Digital Synthesizer DDS, automatic growth control AGC and the operational amplification circuit AMP that connect in turn, Direct Digital Synthesizer DDS produces the controlled cosine signal of frequency, this cosine signal is stablized after amplitude through automatic growth control AGC and is sent to operational amplification circuit AMP, and the signal amplitude received carries out amplifying and is used for driving QCM sensing unit by operational amplification circuit AMP.

Described signal processing unit comprises the first operational amplifier A mp1, second operational amplifier A mp2, first resistance R1, second resistance R2, first analog multiplier multiply1, second analog multiplier multiply2, 3rd analog multiplier multiply3, first low-pass filter LPF1, second low-pass filter LPF2, 3rd low-pass filter LPF3, the wherein output terminal of the reverse input end access reference QCM of the first operational amplifier A mp1, input end grounding in the same way, between the output terminal that first resistance R1 is connected to the first operational amplifier A mp1 and reverse input end, output terminal, the in the same way input end grounding of QCM are measured in the reverse input end access of the second operational amplifier A mp2, between the output terminal that the second resistance R2 is connected to the second operational amplifier A mp2 and reverse input end, two input ends of the first analog multiplier multiply1 are all connected with the output terminal of the first operational amplifier A mp1, and the output terminal of the first analog multiplier multiply1 accesses the first low-pass filter LPF1, an input end of the second analog multiplier multiply2 is connected with the output terminal of the first operational amplifier A mp1, another input end is connected with the output terminal of the second operational amplifier A mp2, and the output terminal of the second analog multiplier multiply2 accesses the second low-pass filter LPF2, two input ends of the 3rd analog multiplier multiply3 are all connected with the output terminal of the second operational amplifier A mp2, output terminal access the 3rd low-pass filter LPF3 of the 3rd analog multiplier multiply3.

The major function of DDS produces the variable cosine signal of frequency keeps, drives QCM to vibrate.Because the fundamental frequency of QCM is near 6MHz, nanogram class precision needs the frequency resolution of <0.3Hz, and the signal frequency of thus DDS generation is within the scope of 0 ~ 10MH, and frequency resolution <0.1Hz just can.

Adopt AD9959 in the present invention, AD9959 chip is that a four-way, internal clock frequencies are up to the Direct Digital Frequency Synthesizers chip of 500MHz.AD9959 produces cosine wave (CW) to drive QCM, for spectrum analysis is ready.The amplitude going out signal due to AD9859 can change along with the change of output frequency, again because for the drive singal of QCM, in order to reduce less desirable vibration interference, it is desirable that the signal that stablizes amplitude.Therefore, automatic growth control (AGC) is added at output terminal.The function of AGC ensures that the peak-to-peak value of sinusoidal signal remains steady state value in frequency of operation section.In the present invention, AD8369 is adopted to be that core builds agc circuit.

Composition graphs 3 ~ 4, the signal acquisition method of double resonance unit of the present invention QCM (Quartz Crystal Microbalance), comprises the following steps:

Step 1, initialization whole system, comprising the initialization of each detection module and host computer interface;

Step 2, arranges the cycle of Single Chip Microcomputer (SCM) system timer;

In detection timer, the cycle set of timer is 1ms, one-time detection is divided into bigness scale and thin survey two steps: during bigness scale, at theoretical resonance frequency f ₀fluctuate in the scope of 1MHz, i.e. [f ₀-1MHz, f ₀+ 1MHz], use the swept frequency of 1KHz ~ 4KHz to scan, draw out the spectrum curve of bigness scale and obtain bigness scale resonance frequency f ₀ ^', then at bigness scale resonance frequency f ₀ ^'fluctuate within the scope of 10KHz, i.e. [f ₀ ^'-10KHz, f ₀ ^'+ 10KHz], select the swept frequency of 10Hz ~ 40Hz to scan.

Step 3, drive signal generator produces the controlled cosine signal of frequency, and this cosine signal drives the reference QCM of QCM sensing unit and detects QCM and produces two-way QCM output signal, specific as follows:

If the output signal of drive singal maker is u=u ₀cos (2 π ft), u ₀for input signal amplitude, f is the frequency of input signal, and the equiva lent impedance measuring QCM is expressed as Z=|Z| ∠ φ, | Z| is the equiva lent impedance modulus value measuring QCM, and φ is the equiva lent impedance angle measuring QCM.With reference to the equiva lent impedance of QCM be expressed as Z '=| Z ' | ∠ φ ', | Z ' | be the equiva lent impedance modulus value with reference to QCM, φ ' be the equiva lent impedance angle of reference QCM.

QCM sensing unit drives the signal obtained after reverse scaling circuit through cosine signal, obtains the output signal u of the first operational amplifier A mp1 respectively ₁' and the output signal u of the second operational amplifier A mp2 ₂', wherein

${u_1}^{\&prime;}=-u_0\frac{R_1}{\left|Z\right|}\cos (2\mathrm{\&pi;ft}-\mathrm{\&phi;})$

${u_2}^{\&prime;}=-u_0\frac{R_2}{\left|Z^{\&prime;}\right|}\cos (2\mathrm{\&pi;ft}-{\mathrm{\&phi;}}^{\&prime;})$

Wherein, R ₁be the resistance value between the output terminal of the first operational amplifier A mp1 and reverse input end, R ₂it is the resistance value between the output terminal of the second operational amplifier A mp2 and reverse input end.

Step 4, two-way QCM outputs signal and adopts correlation principle to carry out processing the frequency and voltage value obtained with reference to QCM and detection QCM through signal processing unit, specific as follows:

Second analog multiplier multiply2 is with reference to QCM and the cross-correlation u detecting QCM output signal by the output after the second low-pass filter LPF2 _f12:

$\begin{array}{c}{u}_{f12}=\frac{1}{T}{\&Integral;}_0^T{u_1}^{\&prime;}\&CenterDot;{u_2}^{\&prime;}\mathrm{dt}\\ =u_0^2\frac{R_1{R}_2}{\left|Z\right|\left|Z^{\&prime;}\right|T}{\&Integral;}_0^T\cos (\mathrm{\&omega;t}-\mathrm{\&phi;})\cos (\mathrm{\&omega;t}-{\mathrm{\&phi;}}^{\&prime;})\mathrm{dt}\\ =u_0^2\frac{R_1{R}_2}{2\left|Z\right|\left|Z^{\&prime;}\right|T}{\&Integral;}_0^T[\cos (\mathrm{\&phi;}-{\mathrm{\&phi;}}^{\&prime;})+\cos (4\mathrm{\&pi;f}-\mathrm{\&phi;}-{\mathrm{\&phi;}}^{\&prime;})]\mathrm{dt}\\ =u_0^2\frac{R_1{R}_2}{2\left|Z\right|\left|Z^{\&prime;}\right|}\cos (\mathrm{\&phi;}-{\mathrm{\&phi;}}^{\&prime;})\end{array}$

Wherein, T=2 π f is the cycle of input signal;

The output of the first analog multiplier multiply1 is the auto-correlation with reference to QCM signal, by after the first low-pass filter LPF1 being:

$u_{f1}=\frac{1}{2}{\left(\frac{u_0{R}_1}{\left|Z\right|}\right)}^2$

U _f1amplitude be output amplitude with reference to QCM;

The output of the 3rd analog multiplier multiply3 is the auto-correlation measuring QCM signal, by after the 3rd low-pass filter LPF3 being:

$u_{f2}=\frac{1}{2}{\left(\frac{u_0{R}_2}{\left|Z\right|}\right)}^2$

U _f2amplitude be and measure the output amplitude of QCM;

According to u _f1and u _f2measurement obtain detecting QCM with reference to the amplitude-versus-frequency curve of QCM, by u _f1, u _f2and u _f12combined Calculation, obtain the phase-frequency characteristic curve between φ-φ ' and frequency sweep.

Step 5, gained frequency and voltage value generates digital signal through A/D converter again and sends to PC through Single Chip Microcomputer (SCM) system;

Step 6, repeat step 3 ~ 5, use swept frequency range is f ₁~ f ₂cosine signal QCM sensing unit is driven, obtained all frequency and voltage values are plotted as spectral characteristic curve, determine with reference to QCM according to this curve and detect the resonance frequency of QCM.

Step 7, after data acquisition system data complete, single-chip microcomputer is used to send collected data to PC by serial ports in real time, the data transmitted are needed to comprise a road magnitude of voltage and each and every one data of frequency values two, in addition, in order to ensure the correctness transmitted, we respectively add a value of statistical indicant before and after the data that will transmit, first value of statistical indicant is 0, and last value of statistical indicant is 1.During transmission, single-chip microcomputer first transmits a value of statistical indicant zero, then sends four experimental datas, finally transmits value of statistical indicant 1, and so, each experimental period needs the data sent to be six.

Step 8, corresponding with the transmission of single-chip microcomputer, be that a unit receives according to every six data when PC receives, the data of this six data corresponding each experimental periods.After each PC receives six data, just judge whether the first data and last data are respectively 0 and 1, if so, just show that middle two is exactly experimental data, processes voltage and frequency respectively, and on spectrum curve, draws a data point in real time; If detect that value of statistical indicant does not meet, just illustrate that this transmission makes mistakes, abandon this group data.By adding zone bit and check bit at experimental data head and the tail, the program that improves distinguishes wrong ability to communication data, and can effectively prevent data to misplace the confusion caused.

In measuring process, the frequency of each measuring period is different, therefore between adjacent experimental period, AD9858 goes out the saltus step process that signal exists different frequency state, and this saltus step not only can cause the existence of a transient process of output signal, and, more seriously, the signal loading of this saltus step process to quartz resonator after, will cause the oscillation phenomenon of a kind of transition state of resonator, this irregular oscillation phenomenon will produce measurement result and have a strong impact on.In order to avoid the impact of this transient process, the time delay adding 10 microseconds between A/D chip frequency control word and AD sampling processing is write in software, the Output rusults of ability Acquisition Circuit after providing one sufficiently long period to make resonator from irregular oscillation recovering state to normal vibration state, as shown in Figure 4.

The task of upper strata PC mainly sets up the communication of PC and single-chip microcomputer, and the operations such as one side gathers the signal of single-chip microcomputer, data processing, real-time drawing function, intelligent computing, can set the parameter such as swept frequency range, frequency step of single-chip microcomputer on the other hand.

Claims (6)

1. the signal pickup assembly of a double resonance unit QCM (Quartz Crystal Microbalance), it is characterized in that, comprise drive signal generator, QCM sensing unit, signal processing unit, A/D converter, Single Chip Microcomputer (SCM) system, PC, wherein drive signal generator, QCM sensing unit, signal processing unit, A/D converter, Single Chip Microcomputer (SCM) system are connected successively, the control end access drive signal generator of Single Chip Microcomputer (SCM) system, the data output end access PC of Single Chip Microcomputer (SCM) system; Described QCM sensing unit comprises with reference to QCM and detects QCM, and signal processing unit adopts correlation principle to reference QCM and detects QCM process;

Described Single Chip Microcomputer (SCM) system controls the communication of the frequency of drive signal generator, the read-write of A/D converter and Single Chip Microcomputer (SCM) system and PC, control word is write to drive signal generator by Single Chip Microcomputer (SCM) system, drive signal generator produces the controlled cosine signal of frequency, this cosine signal drives the reference QCM of QCM sensing unit and detects QCM, two-way QCM outputs signal and adopts after correlation principle process through signal processing unit, generate digital signal through A/D converter again and send to Single Chip Microcomputer (SCM) system, final signal is sent to PC by Single Chip Microcomputer (SCM) system.

2. the signal pickup assembly of double resonance unit according to claim 1 QCM (Quartz Crystal Microbalance), it is characterized in that, described drive signal generator comprises the Direct Digital Synthesizer DDS, automatic growth control AGC and the operational amplification circuit AMP that connect in turn, Direct Digital Synthesizer DDS produces the controlled cosine signal of frequency, this cosine signal is stablized after amplitude through automatic growth control AGC and is sent to operational amplification circuit AMP, and the signal amplitude received carries out amplifying and is used for driving QCM sensing unit by operational amplification circuit AMP.

3. the signal pickup assembly of double resonance unit according to claim 1 QCM (Quartz Crystal Microbalance), it is characterized in that, described signal processing unit comprises the first operational amplifier A mp1, second operational amplifier A mp2, first resistance R1, second resistance R2, first analog multiplier multiply1, second analog multiplier multiply2, 3rd analog multiplier multiply3, first low-pass filter LPF1, second low-pass filter LPF2, 3rd low-pass filter LPF3, the wherein output terminal of the reverse input end access reference QCM of the first operational amplifier A mp1, input end grounding in the same way, between the output terminal that first resistance R1 is connected to the first operational amplifier A mp1 and reverse input end, output terminal, the in the same way input end grounding of QCM are measured in the reverse input end access of the second operational amplifier A mp2, between the output terminal that the second resistance R2 is connected to the second operational amplifier A mp2 and reverse input end, two input ends of the first analog multiplier multiply1 are all connected with the output terminal of the first operational amplifier A mp1, and the output terminal of the first analog multiplier multiply1 accesses the first low-pass filter LPF1, an input end of the second analog multiplier multiply2 is connected with the output terminal of the first operational amplifier A mp1, another input end is connected with the output terminal of the second operational amplifier A mp2, and the output terminal of the second analog multiplier multiply2 accesses the second low-pass filter LPF2, two input ends of the 3rd analog multiplier multiply3 are all connected with the output terminal of the second operational amplifier A mp2, output terminal access the 3rd low-pass filter LPF3 of the 3rd analog multiplier multiply3.

4., based on a signal acquisition method for the double resonance unit QCM (Quartz Crystal Microbalance) of device described in claim 1, it is characterized in that, comprise the following steps:

Step 1, initialization whole system, comprising the initialization of each detection module and host computer interface;

Step 2, arranges the cycle of Single Chip Microcomputer (SCM) system timer;

Step 3, drive signal generator produces the controlled cosine signal of frequency, and this cosine signal drives the reference QCM of QCM sensing unit and detects QCM and produces two-way QCM output signal;

Step 4, two-way QCM outputs signal and adopts correlation principle to carry out processing the frequency and voltage value obtained with reference to QCM and detection QCM through signal processing unit;

Step 5, gained frequency and voltage value generates digital signal through A/D converter again and sends to PC through Single Chip Microcomputer (SCM) system;

Step 6, repeat step 3 ~ 5, use swept frequency range is f ₁~ f ₂cosine signal QCM sensing unit is driven, obtained all frequency and voltage values are plotted as spectral characteristic curve, determine with reference to QCM according to this curve and detect the resonance frequency of QCM.

5. the signal acquisition method of double resonance unit according to claim 4 QCM (Quartz Crystal Microbalance), is characterized in that, arrange the cycle of Single Chip Microcomputer (SCM) system timer described in step 2, specific as follows:

In detection timer, the cycle set of timer is 1ms, one-time detection is divided into bigness scale and thin survey two steps: during bigness scale, at theoretical resonance frequency f ₀fluctuate in the scope of 1MHz, i.e. [f ₀-1MHz, f ₀+ 1MHz], use the swept frequency of 1KHz ~ 4KHz to scan, draw out the spectrum curve of bigness scale and obtain bigness scale resonance frequency f ₀', then at bigness scale resonance frequency f ₀' fluctuate within the scope of 10KHz, i.e. [f ₀'-10KHz, f ₀'+10KHz], select the swept frequency of 10Hz ~ 40Hz to scan.

6. the signal acquisition method of double resonance unit according to claim 4 QCM (Quartz Crystal Microbalance), it is characterized in that, two-way QCM described in step 4 outputs signal and adopts correlation principle to carry out processing the frequency and voltage amplitude obtained with reference to QCM and detection QCM through signal processing unit, specific as follows:

Second analog multiplier multiply2 is with reference to QCM and the cross-correlation u detecting QCM output signal by the output after the second low-pass filter LPF2 _f12:

$\begin{array}{c}{u}_{f12}=\frac{1}{T}{\&Integral;}_0^T{u_1}^{\&prime;}\&CenterDot;{u_2}^{\&prime;}\mathrm{dt}\\ =u_0^2\frac{R_1{R}_2}{\left|Z\right|\left|Z^{\&prime;}\right|T}{\&Integral;}_0^T\cos (\mathrm{\&omega;t}-\mathrm{\&phi;})\cos (\mathrm{\&omega;t}-{\mathrm{\&phi;}}^{\&prime;})\mathrm{dt}\\ =u_0^2\frac{R_1{R}_2}{2\left|Z\right|\left|Z^{\&prime;}\right|T}{\&Integral;}_0^T[\cos (\mathrm{\&phi;}-{\mathrm{\&phi;}}^{\&prime;})+\cos (4\mathrm{\&pi;f}-\mathrm{\&phi;}-{\mathrm{\&phi;}}^{\&prime;})]\mathrm{dt}\\ =u_0^2\frac{R_1{R}_2}{2\left|Z\right|\left|Z^{\&prime;}\right|}\cos (\mathrm{\&phi;}-{\mathrm{\&phi;}}^{\&prime;})\end{array}$

Wherein, T=2 π f is the cycle of input signal, and f is the frequency of input signal, be the output of the first operational amplifier A mp1, be the output of the second operational amplifier A mp2, Z=|Z| ∠ φ is the equiva lent impedance measuring QCM, | Z| is the equiva lent impedance modulus value measuring QCM, φ is the equiva lent impedance angle measuring QCM, Z '=| Z ' | ∠ φ ' is the equiva lent impedance with reference to QCM, | Z ' | be the equiva lent impedance modulus value with reference to QCM, φ ' is the equiva lent impedance angle with reference to QCM, R ₁be the resistance value between the output terminal of the first operational amplifier A mp1 and reverse input end, R ₂be the resistance value between the output terminal of the second operational amplifier A mp2 and reverse input end, u ₀for the amplitude of input signal;

The output of the first analog multiplier multiply1 is the auto-correlation with reference to QCM signal, by after the first low-pass filter LPF1 being:

$u_{f1}=\frac{1}{2}{\left(\frac{u_0{R}_1}{\left|Z\right|}\right)}^2$

U _f1amplitude be output amplitude with reference to QCM;

The output of the 3rd analog multiplier multiply3 is the auto-correlation measuring QCM signal, by after the 3rd low-pass filter LPF3 being:

$u_{f2}=\frac{1}{2}{\left(\frac{u_0{R}_2}{\left|Z\right|}\right)}^2$

U _f2amplitude be and measure the output amplitude of QCM;

According to u _f1and u _f2measurement obtain detecting QCM with reference to the amplitude-versus-frequency curve of QCM, by u _f1, u _f2and u _f12combined Calculation, obtain the phase-frequency characteristic curve between φ-φ ' and frequency sweep.