CN207039545U - Frequency tripling QCM circuit systems based on Digital Frequency Synthesize - Google Patents
Frequency tripling QCM circuit systems based on Digital Frequency Synthesize Download PDFInfo
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- CN207039545U CN207039545U CN201720886413.3U CN201720886413U CN207039545U CN 207039545 U CN207039545 U CN 207039545U CN 201720886413 U CN201720886413 U CN 201720886413U CN 207039545 U CN207039545 U CN 207039545U
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Abstract
The utility model provides a kind of frequency tripling QCM circuit systems based on Digital Frequency Synthesize, including the loop being followed in series to form by controller, digital frequency synthesizer, quartz crystal oscillator, load resistance and voltage, current sample and phase difference measuring circuit；The controller synthesizes a series of single frequency sinusoidal ripples by low frequency to high frequency in certain frequency range by digital frequency synthesizer by setpoint frequency step value, and the sine wave vibrates to encourage quartz crystal to produce.When three rank series resonance frequency of the frequencies span quartz crystal oscillator of synthesis sine, flow through quartz crystal oscillator and the electric current of load resistance and sign change occurs with the phase difference of load resistance both end voltage, three rank resonant frequencies of quartz crystal oscillator can be obtained by recording frequency values corresponding to the catastrophe point.
Description
Technical field
It the utility model is related to frequency tripling QCM circuit systems, more particularly to a kind of frequency tripling based on Digital Frequency Synthesize
QCM circuit systems.
Background technology
At present, quartz crystal microbalance is mainly used in measuring molecular contamination, fluid density etc., and used oscillating circuit is basic
For traditional classical oscillator circuits form, predominantly Colpitts oscillation circuit, its major defect be circuit resonance scope compared with
Narrow (a few KHzs), and higher (when Q values are relatively low can not normal starting of oscillation) be required to quartz crystal Q values, therefore cause to measure
Narrow range.
QCM (QCM) is a kind of sensor for changing sensitivity to interface, and it is quick to interface quality change
Sense degree reaches nanogram level, therefore it is in subjects such as physics, chemistry, biology, materia medica, clinical medicine, environmental sciences
Certain application is obtained in interface problem research, turns into researcher extensive concern and the new sensing paid attention to and measurement side
Method.
Principle is the inverse piezoelectric effect using quartz crystal, and quartz crystal can produce shaking for certain frequency under alternating electric field
Dynamic, this vibration is relevant with the quality of crystal；If plane of crystal has material absorption, the change of quality can change vibration frequency
Become, produce frequency displacement.Qcm sensor has existed as a kind of high sensitivity, high stability, fast, the low-cost senser element of response
Various fields are applied.The applications of QCM in the detection are broadly divided into application in the gas phase and application in the liquid phase, and it is surveyed
Measuring mechanism is mainly：Because the resonance characteristic of quartz crystal can change with the mass change of its surface mass, therefore, pass through
The change can for detecting its resonance characteristic analyzes the situation of change of surface quality.And the change of quality be probably by physics,
Caused by chemistry and biological respinse.In biochemistry detection, in order to complete the measurement to detected material, the generally electricity in crystal
Pole surface plates the sensitive membrane that can be reacted with detected material, and thus, the situation can of biochemical reaction passes through analyzing crystal resonance
The change of characteristic and obtain.
Existing QCM is as sensor, by gold-plated extraction electrode thereon using monocrystal.In order to measure crystal
Resonance characteristic, conventional method has three kinds, i.e. oscillating circuit method, Impedance Analysis and attenuation analysis method.Oscillating circuit method is
The method generally used, has that price is low, integrated level is high, high resolution and swift feature；Impedance Analysis can provide
More complete information, but laboratory environment is typically limited to, price is high and volume is larger；The attenuation analysis method of pulse excitation has
The characteristics of not influenceed by circuit, there is higher precision.
However, one of greatest problem that QCM faces in the application is affected by environment larger, especially temperature, although adopting
With the crystal of AT- cuttings can will ground temperature sensitiveness, but its performance still can not meet the requirement of high-acruracy survey.Separately
One problem is in solution environmental, and QCM frequency responses depend not only upon surface and become with quality caused by analyte interaction
Change, at the same it is inseparable with the effect of surrounding medium.Briefly, the quality increase of the material vibrated together with chip can cause
The decline of frequency, but the viscoplasticity for vibrating material becomes the big rising for then showing as frequency, therefore, the analysis of QCM data quantitatives
Complexity causes the popularization and application of liquid phase QCM so far.
With the raising required accuracy of detection, in order to overcome electrode surface roughness, porous, fluid pressure and temperature
The influence of the factor to measurement accuracy such as degree, solution viscosity and density and conductance of liquid, occurs by improving frequency of oscillation to carry
The Resonance measuring method of high measurement accuracy and the polycrystal mensuration for passing through multichannel measurement of comparison.Wherein multichannel is formed and mainly had
2 kinds of methods, i.e., multiple measurement energy roads and polycrystal are constructed on monocrystal and form sensor array.Based single crystal body structure is more logical
Road makes processing technology complicated, and is influenced each other between multichannel, therefore the method for polycrystal structure sensor array, except can have
Effect is overcome outside the influence of environmental factor, can also be completed by plating different sensitive membranes on different crystal surface to the more of analyte
Angular surveying or disposable detection to various composition contained by something or measurement are future developing trends.
Therefore, it is particularly important the problem of quartz crystal oscillator failure of oscillation under big damping condition when how to solve to use bandpass filter.
Utility model content
In order to solve the above problems, the utility model provides a kind of frequency tripling QCM circuits system based on Digital Frequency Synthesize
System, including by controller, digital frequency synthesizer, quartz crystal oscillator, load resistance and voltage, current sample and phase difference measurement
The loop that circuit is followed in series to form；
The frequency tripling QCM circuit systems also include multichannel switching switch, and the digital frequency synthesizer passes through simulation
Switch timesharing and drive four road quartz crystal oscillators, there is independent load circuit loop per quartz crystal oscillator all the way, and by quartz crystal oscillator
Voltage and current signal is by individually sampling, modulate circuit inputs to controller；The different passages of measurement of controller time-sharing multiplex
Resonant frequency.
Preferably, closed in the digital frequency synthesizer from Digital Frequency Synthesize chip AD9854, the numerical frequency
Into chip AD9854 by there is source crystal oscillator U3 (125MHz) to provide benchmark all the time.
Preferably, the voltage, current sample and phase difference measuring circuit are described from phase difference measurement chip AD8302
Voltage, current sample and phase difference measuring circuit also include electric current, voltage collection circuit, for being sampled to electric current, voltage
And compare phase difference；Two of quartz crystal oscillator and the voltage at load resistance both ends difference input phase difference measurements chip AD8302 are logical
Road, the output voltage of the phase difference measurement chip AD8302 are proportional to quartz crystal oscillator and the voltage-phase at load resistance both ends
Difference；When output voltage is 0, then quartz crystal oscillator vibration is in its series resonance frequency.
Preferably, the resonant frequency of the quartz crystal oscillator is three rank resonant frequencies；The three ranks resonant frequency is 15MHz.
Preferably, the initial frequency of controller setting and to terminate frequency be respectively 14.5MHz and 15.5MHz, with
10MHz is the output waveform and amplitude that step value controls the digital frequency synthesizer, and the sine wave signal of the synthesis passes through
Coaxial cable is connected to quartz crystal oscillator and load resistance, for encouraging quartz crystal oscillator, controls the voltage, current sample and phase
Difference measurements circuit measures the phase difference of voltage and electric current in each frequency and judges its symbol, quartz crystal oscillator and load resistance both ends
Voltage sampled by voltage collection circuit after compare phase difference；Continue to change frequency synthesis if voltage-phase is ahead of electric current,
Otherwise the frequency values recorded now export as three rank series resonance frequency values of quartz crystal oscillator.Enter line frequency in the controller
The workflow of rate search is as shown in Figure 4.
Frequency tripling QCM circuit systems described in the utility model also include FT232 chips, for the serial ports of controller to be turned
USB interface is turned to, is communicated with host computer.
Controller described in the utility model is by digital frequency synthesizer in certain frequency range (14.5-15.5MHz) by low frequency
A series of single frequency sinusoidal ripples are synthesized by setpoint frequency step value to high frequency, the sine wave shakes to encourage quartz crystal to produce
Swing.When three rank series resonance frequency of the frequencies span quartz crystal oscillator of synthesis sine, quartz crystal oscillator and load resistance are flowed through
The phase difference of electric current and load resistance both end voltage sign change occurs, recording frequency values corresponding to the catastrophe point can obtain
Three rank resonant frequencies of quartz crystal oscillator.
The beneficial effects of the utility model are：
1st, compared with the QCM using fundamental frequency, the utility model uses the QCM using high-order harmonic wave, first, high sensitivity, right
It should change in identical surface quality, the frequency change of nth harmonic is n times of fundamental frequency；Second, surface sensitive is good, nth harmonic
Wavelength be fundamental frequency wavelength 1/n, because effective detecting depths of the QCM on crystal oscillator surface is about a wavelength, high-order harmonic wave QCM
Spatial resolution it is higher.
2nd, compared with the trebling circuit system based on band-pass filtering method：First, circuit design is simple, it is not necessary to simulates
Circuit；The two QCM detections applied under big damping condition, the output drive voltage of wherein digital frequency synthesizer is adjustable, easily
In solving the problems, such as bandpass filtering scheme quartz crystal oscillator failure of oscillation under big damping condition.
It should be appreciated that foregoing description substantially and follow-up description in detail are exemplary illustration and explanation, should not
As the limitation to the claimed content of the utility model.
Brief description of the drawings
With reference to the accompanying drawing enclosed, the more purposes of the utility model, function and advantage will pass through the utility model embodiment party
The described below of formula is illustrated, wherein：
Fig. 1 schematically shows the frequency tripling QCM circuit system block diagrams of the present utility model based on Digital Frequency Synthesize.
Fig. 2 diagrammatically illustrates the Digital Frequency Synthesize circuit diagram of the present utility model.
Fig. 3 diagrammatically illustrates voltage, current sample and phase difference measuring circuit figure of the present utility model.
Fig. 4 diagrammatically illustrates resonant frequency search routine figure of the present utility model.
Embodiment
By reference to one exemplary embodiment, the purpose of this utility model and function and for realizing these purposes and function
Method will be illustrated.However, the utility model is not limited to one exemplary embodiment as disclosed below；Can be by not
It is realized with form.The essence of specification is only to aid in various equivalent modifications Integrated Understanding the utility model
Detail.
Hereinafter, embodiment of the present utility model will be described with reference to the drawings.In the accompanying drawings, identical reference represents
Same or similar part, or same or like step.
Embodiment 1
Referring to Fig. 1, a kind of frequency tripling QCM circuit systems based on Digital Frequency Synthesize, including by controller, numerical frequency
The loop that synthesizer, quartz crystal oscillator, load resistance and voltage, current sample and phase difference measuring circuit are followed in series to form；
The frequency tripling QCM circuit systems also include multichannel switching switch, and the digital frequency synthesizer passes through simulation
Switch timesharing and drive four road quartz crystal oscillators, there is independent load circuit loop per quartz crystal oscillator all the way, and by quartz crystal oscillator
Voltage and current signal is by individually sampling, modulate circuit inputs to controller；The different passages of measurement of controller time-sharing multiplex
Resonant frequency.
Referring to Fig. 2, the digital frequency synthesizer selects Digital Frequency Synthesize chip AD9854, the Digital Frequency Synthesize
Chip AD9854 is by there is source crystal oscillator U3 (125MHz) to provide benchmark all the time.
The voltage, current sample and phase difference measuring circuit select phase difference measurement chip AD8302, quartz crystal oscillator and
The voltage difference input phase difference measurements chip AD8302 at load resistance both ends two passages, the phase difference measurement chip
AD8302 output voltage is proportional to quartz crystal oscillator and the voltage phase difference at load resistance both ends；When output voltage is 0, then stone
English crystal oscillator is vibrated in its series resonance frequency.
When series resonance occurs for the quartz crystal oscillator, its overall impedance shows as purely resistive, voltage and current phase difference
For 0., can be by comparing quartz crystal oscillator and load electricity because the voltage at load resistance both ends and the current and phase difference that flows through are always 0
The voltage phase difference for hindering both ends judges the oscillatory regime of crystal oscillator.
Referring to Fig. 3, voltage Out A and Out B the difference input phase difference measurements chips at crystal oscillator and load resistance both ends
AD8302 two passages INPA and INPB, the output voltage Phase out of chip are proportional to Out A and Out B phase difference.
When output voltage Phase out are 0, it is believed that crystal oscillator is vibrated in its series resonance frequency.
Referring to Fig. 4, Fig. 4 show the workflow that frequency search is carried out in the controller.The controller setting
Initial frequency and termination frequency are respectively 14.5MHz and 15.5MHz, and the Digital Frequency Synthesize is controlled by step value of 10MHz
The output waveform and amplitude of device, the sine wave signal sequentially generated are connected to quartz crystal oscillator and load resistance by coaxial cable,
For encouraging quartz crystal oscillator, the controller controls voltage, current sample and the phase difference measuring circuit to be surveyed in each frequency
The phase difference of amount voltage and electric current simultaneously judges its symbol, when three rank series resonances of the frequencies span quartz crystal oscillator of synthesis sine
During frequency, flow through quartz crystal oscillator and the electric current of load resistance and sign change, note occurs with the phase difference of load resistance both end voltage
The three rank resonant frequency values that frequency values corresponding to the catastrophe point are recorded as quartz crystal oscillator export；If voltage-phase is ahead of electric current
Continue to change frequency synthesis.
The utility model uses Digital Frequency Synthesize chip, and by MCU driving DDS chips, DDS is done by High Precision Crystal Oscillator
Clock source, order-driven DDS chips export the accurate square wave of assigned frequency, are applied on plated film crystal workpiece, for driving stone
English crystal oscillator, by measuring voltage current phase difference, it is scanned in the band frequency centered on 15MHz, in theory, plated film is brilliant
Capacitive can be presented in resonance point side for body, and perception can be presented in opposite side, during scanning, if obtaining voltage, electric current phase
Position transfer point, you can it is resonance point to think the point.
Frequency tripling QCM circuit systems described in the utility model also include FT232 chips, for the serial ports of controller to be turned
USB interface is turned to, is communicated with host computer.
The utility model uses digital frequency synthesis technology (abbreviation DDS), and assigned frequency is actively being sent just by controller
String ripple drives quartz crystal oscillator, devises voltage, current sample and phase difference measuring circuit to measure voltage current phase difference, and
Scan 15MHz or so resonance point.Frequency tripling QCM circuit systems provided by the utility model based on Digital Frequency Synthesize,
In batch production, cost can be effectively reduced.
With reference to the explanation of the present utility model disclosed here and practice, other embodiment of the present utility model is for this area
Technical staff will be readily apparent and understand.Illustrate and embodiment be to be considered only as it is exemplary, it is of the present utility model really
Scope and spirit are defined in the claims.
Claims (7)
1. a kind of frequency tripling QCM circuit systems based on Digital Frequency Synthesize, it is characterised in that including by controller, numeral frequency
What rate synthesizer, quartz crystal oscillator, load resistance and voltage, current sample and phase difference measuring circuit were followed in series to form returns
Road.
2. circuit system according to claim 1, it is characterised in that the frequency tripling QCM circuit systems also include more logical
Road switching switch, the digital frequency synthesizer drives four road quartz crystal oscillators by analog switch timesharing, per quartz crystal oscillator all the way
With independent load circuit loop, and by the voltage and current signal of quartz crystal oscillator by individually sampling, modulate circuit input
To controller；The resonant frequency of the different passages of measurement of controller time-sharing multiplex.
3. circuit system according to claim 1, it is characterised in that numerical frequency is selected in the digital frequency synthesizer
Synthesis chip AD9854, the Digital Frequency Synthesize chip AD9854 are by there is source crystal oscillator U3 to provide benchmark all the time.
4. circuit system according to claim 1, it is characterised in that the voltage, current sample and phase difference measurement electricity
Phase difference measurement chip AD8302 is selected on road, and the voltage, current sample and phase difference measuring circuit also include electric current, voltage is adopted
Two of the voltage difference input phase difference measurements chip AD8302 at collector, the quartz crystal oscillator and the load resistance both ends
Passage.
5. circuit system according to claim 1, it is characterised in that the initial frequency and termination frequency of the controller setting
Rate is respectively 14.5MHz and 15.5MHz, controls the output waveform of the digital frequency synthesizer as step value using 10MHz and shakes
Width, the sine wave signal of the synthesis are connected to quartz crystal oscillator and load resistance by coaxial cable, and the controller controls institute
Voltage, current sample and phase difference measuring circuit is stated to measure the phase difference of voltage and electric current in each frequency and judge its symbol,
Quartz crystal oscillator and the voltage at load resistance both ends compare phase difference after being sampled by voltage collection circuit.
6. circuit system according to claim 1, it is characterised in that the frequency tripling QCM circuit systems also include FT232
Chip, for the serial ports of controller to be converted into USB interface, communicated with host computer.
7. circuit system according to claim 1, it is characterised in that the resonant frequency of the quartz crystal oscillator is three rank resonance
Frequency；The three ranks resonant frequency is 15MHz.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113163871A (en) * | 2018-12-11 | 2021-07-23 | 尼科创业贸易有限公司 | Aerosol-generating device and method of operating the same |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113163871A (en) * | 2018-12-11 | 2021-07-23 | 尼科创业贸易有限公司 | Aerosol-generating device and method of operating the same |
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