CN110440883B - Static capacitance compensation circuit and method of quartz crystal microbalance - Google Patents

Static capacitance compensation circuit and method of quartz crystal microbalance Download PDF

Info

Publication number
CN110440883B
CN110440883B CN201910653127.6A CN201910653127A CN110440883B CN 110440883 B CN110440883 B CN 110440883B CN 201910653127 A CN201910653127 A CN 201910653127A CN 110440883 B CN110440883 B CN 110440883B
Authority
CN
China
Prior art keywords
operational amplifier
resistor
throw switch
double
pole double
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201910653127.6A
Other languages
Chinese (zh)
Other versions
CN110440883A (en
Inventor
马英明
刘振邦
包宇
牛利
王伟
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Guangzhou University
Original Assignee
Guangzhou University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Guangzhou University filed Critical Guangzhou University
Priority to CN201910653127.6A priority Critical patent/CN110440883B/en
Publication of CN110440883A publication Critical patent/CN110440883A/en
Application granted granted Critical
Publication of CN110440883B publication Critical patent/CN110440883B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01G—WEIGHING
    • G01G3/00—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances
    • G01G3/12—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing
    • G01G3/16—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing measuring variations of frequency of oscillations of the body
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/02—Analysing fluids
    • G01N29/022—Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N5/00—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M1/00—Analogue/digital conversion; Digital/analogue conversion
    • H03M1/12—Analogue/digital converters
    • H03M1/1205—Multiplexed conversion systems

Abstract

The invention discloses a static capacitance compensation circuit and a method of a quartz crystal microbalance, wherein the static capacitance compensation circuit comprises a potential control unit, a direct current control unit, a static capacitance compensation unit, a signal attenuation unit and a signal acquisition unit; the scheme is that a variable capacitance diode is added in a circuit, the capacitance of the variable capacitance diode is controlled by a direct current control unit, and an alternating voltage is applied to the variable capacitance diode to ensure that the current passing through the variable capacitance diode is equal to the current flowing through a quartz crystal static capacitor in magnitude and mutually offset, so that the purpose of capacitance compensation is achieved; the operational amplifier and the variable capacitance diode form a capacitance compensation unit, the quartz crystal static capacitance is accurately compensated, the automatic compensation of the static capacitance is realized, and the compensation accuracy and stability are good. The capacitance compensation range is as follows: 2pF-30pF, and capacitance compensation precision +/-2 pF.

Description

Static capacitance compensation circuit and method of quartz crystal microbalance
Technical Field
The invention relates to the technical field of electronic circuits, in particular to a static capacitance compensation circuit and a static capacitance compensation method for a quartz crystal microbalance.
Background
The Quartz Crystal Microbalance (QCM) is a quality detection instrument which is very sensitive to interface change, the measurement precision of the QCM can reach nanogram level, and the most basic principle is that the piezoelectric effect of quartz crystal is utilized. The AT-cut quartz wafer adopted by the QCM belongs to a thickness shear model resonator, the characteristic of the quartz wafer during working is similar to that of an RLC series-parallel circuit, the quartz wafer comprises two branches (a static circuit and a dynamic circuit), and the dynamic circuit is formed by connecting equivalent resistors, equivalent capacitors and equivalent inductors in series. The static circuit is formed by a parallel capacitor (also called static capacitor). The static capacitance is an additional capacitance caused by metal electrodes plated on two sides of the quartz wafer and electrode leads, and when the load of the quartz wafer is small, the static capacitance is small (several pF), and the influence of the static capacitance on circuit resonance is small and negligible. When the viscoelasticity of the coating material on the surface of the crystal electrode is large or the electrode is in a liquid phase, the equivalent resistance and the parallel capacitance are increased, the amplitude-frequency and phase-frequency characteristics of the quartz wafer are affected, and the reason why the self-excited oscillation circuit is usually stopped under a large damping environment is also provided. Therefore, the influence of the static capacitance must be eliminated.
The traditional circuit adopts a method of generating a negative capacitor to offset the static capacitor, and manually adjusting the compensation capacitor until the compensation capacitor is close to the static capacitor so as to enable the oscillating circuit to work in a series resonance state. The traditional capacitance compensation method needs manual compensation, and has the disadvantages of complex compensation and low precision.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a static capacitance compensation circuit and a static capacitance compensation method for a quartz crystal microbalance.
The purpose of the invention is realized by the following technical scheme:
a static capacitance compensation circuit for a quartz crystal microbalance comprising: the device comprises a potential control unit, a direct current control unit, a static capacitance compensation unit, a signal attenuation unit and a signal acquisition unit; the potential control unit includes: an operational amplifier A1, an operational amplifier A2, an operational amplifier A3, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a single-pole double-throw switch S1, a double-pole double-throw switch S2 and a quartz crystal X1 to be capacitance-compensated; the positive pole of a signal source V2 is connected with the non-inverting input end of an operational amplifier A1, the output end of the operational amplifier A1 is connected with the non-inverting input end of an operational amplifier A2, the output end of the operational amplifier A2 is connected with the first fixed end of a double-pole double-throw switch S2 through a resistor R1, the output end of the operational amplifier A2 is further connected with the second fixed end of the double-pole double-throw switch S2 through a resistor R2, the output end of the operational amplifier A2 is further connected with the third fixed end of the double-pole double-throw switch S2 through a resistor R3, the output end of the operational amplifier A2 is further connected with the fourth fixed end of the double-pole double-throw switch S2 through a resistor R4, the first fixed end of the double-pole double-throw switch S2 is connected with the first fixed end of the single-pole double-throw switch S1, the second fixed end of the double-pole double-throw switch S2 is connected with the second fixed end of the single-pole double-throw switch S5, the second fixed end of the single-pole double-throw switch S5857324 is, the other end of the quartz crystal X1 to be capacitance compensated is connected to the ground; one end of the quartz crystal X1 to be capacitance compensated is also connected with the non-inverting input end of the operational amplifier A3, and the inverting input end and the output end of the operational amplifier A3 are both connected with the inverting input end of the operational amplifier A2; the static capacitance compensation unit includes: an operational amplifier A1, an operational amplifier A5, a resistor R10, a resistor R11, a capacitor C1 and a varactor diode D1; the inverting input end of the operational amplifier A1 is connected with the output end of the operational amplifier A1 and the non-inverting input end of the operational amplifier A5, the inverting input end of the operational amplifier A5 is connected to the ground through a resistor R10, the inverting input end of the operational amplifier A5 is also connected with one end of a capacitor C1 and the output end of the operational amplifier A5 through a resistor R11, the other end of the capacitor C1 is connected with the negative electrode of a variable-capacitance diode D1, and the positive electrode of the variable-capacitance diode D1 is connected with one end of a quartz crystal X1 to be capacitance-compensated; the direct current control unit includes: an operational amplifier A6, a direct current source V1, a resistor R12 and an inductor L1; the negative electrode of the direct current source V1 is connected to the ground, the positive electrode of the direct current source V1 is connected with the non-inverting input end of the operational amplifier A6, the inverting input end of the operational amplifier A6 is connected with the output end of the operational amplifier A6 and one end of the resistor R12, and the other end of the resistor R12 is connected with the negative electrode of the varactor D1 through the inductor L1; the signal attenuation unit includes: an operational amplifier A4, a single-pole double-throw switch S3, a double-pole double-throw switch S4, a resistor R5, a resistor R6, a resistor R7, a resistor R8 and a resistor R9; the non-inverting input end of the operational amplifier A4 is connected with the output end of the operational amplifier A2, the inverting input end of the operational amplifier A4 is connected with the output end of the operational amplifier A4, the inverting input end of the operational amplifier A4 is also connected with the moving end of the single-pole double-throw switch S3 through a resistor R5, the first and second moving ends of the single-pole double-throw switch S3 are respectively connected with the first and second moving ends of the double-pole double-throw switch S4, and the first, second, third and fourth moving ends of the double-pole double-throw switch S4 are respectively connected to the ground through a resistor R6, a resistor R7, a resistor R8 and a resistor R9; the signal acquisition unit includes: an analog multiplier a7, an analog multiplier A8, a low-pass filtering module LP1, a low-pass filtering module LP2, an analog-to-digital converter ADC1 and an analog-to-digital converter ADC 2; the negative pole of the signal source V3 is connected to the ground, the positive pole of the signal source V3 is connected to the second input terminal of the analog multiplier A7, the output terminal of the analog multiplier A7 is connected to the analog-to-digital converter ADC1 through the low-pass filtering module LP1, the negative pole of the signal source V2 is connected to the ground, the positive pole of the signal source V2 is connected to the second input terminal of the analog multiplier a8, the output terminal of the analog multiplier a8 is connected to the analog-to-digital converter ADC2 through the low-pass filtering module LP2, and the first input terminal of the analog multiplier A7 and the first input terminal of the analog multiplier a8 are both connected to one.
Preferably, signal source V2 is a cosine signal, signal source V3 is a sine signal, and signal source V1 is a dc source.
A static capacitance compensation method of a quartz crystal microbalance comprises the following steps:
s1, setting the single-pole double-throw switch S3 and the double-pole double-throw switch S4 to be attenuation maximum values, and setting the single-pole double-throw switch S1 and the double-pole double-throw switch S2 to be amplification minimum values;
s2, outputting the maximum voltage from the signal source V1, and using the signal source V1 as a direct current signal source;
s3, adjusting the frequency of the output signals of the signal source V2 and the signal source V3 to enable the frequency of the output signals of the signal source V2 and the signal source V3 to be close to the resonance frequency of the quartz crystal X1 to be capacitance compensated, wherein the signal source V2 and the signal source V3 are orthogonal waves with equal frequency, equal amplitude and 90-degree phase difference;
s4, collecting the voltage through ADC1 and ADC2 to obtain voltage VNet6Amplitude-frequency characteristics and phase-frequency characteristics of;
s5, according to the voltage VNet6The single-pole double-throw switch S1, the double-pole double-throw switch S2, the single-pole double-throw switch S3 and the double-pole double-throw switch S4 are switched according to the amplitude-frequency characteristic and the phase-frequency characteristic, so that the amplification factor of a quartz crystal X1 to be subjected to capacitance compensation reaches a preset multiple, and the input amplitude of an analog multiplier A7 and an analog multiplier A8 reaches a preset amplitude; recordingThe frequency offset difference of (a); wherein the frequency offset difference is the voltage V output by the operational amplifier A2Net6The frequency corresponding to the maximum amplitude value and the voltage V output by the operational amplifier A2Net6The difference in frequency corresponding to the phase zero;
s6, sequentially reducing the output of the signal source V1 and changing the compensation value of the variable capacitance diode; and (5) repeating the steps 3, 4 and 5 until the signal source V1 outputs the lower limit value of the preset voltage, recording all frequency deviation differences, and searching the output voltage of the signal source V1 corresponding to the minimum frequency deviation difference as a static capacitance compensation voltage value point.
Compared with the prior art, the invention has the following advantages:
in the scheme, a variable capacitance diode is added in a circuit, the capacitance of the variable capacitance diode is controlled by a direct current control unit, and an alternating voltage is applied to the variable capacitance diode to ensure that the current passing through the variable capacitance diode is equal to the current flowing through a quartz crystal static capacitor in magnitude and offset with each other, so that the purpose of capacitance compensation is achieved; the operational amplifier and the variable capacitance diode form a capacitance compensation unit, the quartz crystal static capacitance is accurately compensated, the automatic compensation of the static capacitance is realized, and the compensation accuracy and stability are good. The static capacitance compensation range of the scheme is as follows: 2pF-30pF, and capacitance compensation precision +/-2 pF.
Drawings
Fig. 1 is a circuit diagram of a static capacitance compensation circuit of the quartz crystal microbalance of the present invention.
FIG. 2 is an equivalent circuit model diagram of a quartz crystal X1 to be capacitance compensated according to the present invention.
FIG. 3 is a graph showing the amplitude-frequency-phase-frequency characteristics of the quartz crystal X1 of the present invention at no load.
FIG. 4(a) is a graph showing the amplitude-frequency-phase-frequency characteristics of the quartz crystal X1 before capacitance compensation in the liquid phase of the present invention.
FIG. 4(b) is a graph showing the amplitude-frequency-phase-frequency characteristics of the quartz crystal X1 after capacitance compensation in the liquid phase according to the present invention.
FIG. 5 is a test chart of the static capacitance compensation accuracy of the quartz crystal X1 of the present invention.
Detailed Description
The invention is further illustrated by the following figures and examples.
Referring to fig. 1, a static capacitance compensation circuit of a quartz crystal microbalance includes: the device comprises a potential control unit, a direct current control unit, a static capacitance compensation unit, a signal attenuation unit and a signal acquisition unit;
the potential control unit includes: an operational amplifier A1, an operational amplifier A2, an operational amplifier A3, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a single-pole double-throw switch S1, a double-pole double-throw switch S2 and a quartz crystal X1 to be capacitance-compensated; the positive pole of a signal source V2 is connected with the non-inverting input end of an operational amplifier A1, the output end of the operational amplifier A1 is connected with the non-inverting input end of an operational amplifier A2, the output end of the operational amplifier A2 is connected with the first fixed end of a double-pole double-throw switch S2 through a resistor R1, the output end of the operational amplifier A2 is further connected with the second fixed end of the double-pole double-throw switch S2 through a resistor R2, the output end of the operational amplifier A2 is further connected with the third fixed end of the double-pole double-throw switch S2 through a resistor R3, the output end of the operational amplifier A2 is further connected with the fourth fixed end of the double-pole double-throw switch S2 through a resistor R4, the first fixed end of the double-pole double-throw switch S2 is connected with the first fixed end of the single-pole double-throw switch S1, the second fixed end of the double-pole double-throw switch S2 is connected with the second fixed end of the single-pole double-throw switch S5, the second fixed end of the single-pole double-throw switch S5857324 is, the other end of the quartz crystal X1 to be capacitance compensated is connected to the ground; one end of the quartz crystal X1 to be capacitance compensated is also connected with the non-inverting input end of the operational amplifier A3, and the inverting input end and the output end of the operational amplifier A3 are both connected with the inverting input end of the operational amplifier A2;
in the circuit of the potential control unit, an alternating current signal source V2, V3 are orthogonal alternating current signals, a signal source V2 is a cosine signal, a signal source V3 is a sine signal, the signal source V2 is applied to the in-phase end of an operational amplifier A2 through a voltage follower A1 (an operational amplifier A1), the output of the operational amplifier A2 acts on one end of a quartz crystal X1 to be capacitance-compensated through an optional resistor (a resistor R1 or a resistor R2 or a resistor R3 or a resistor R4), and simultaneously, the node 10 (one end of the quartz crystal X1 to be capacitance-compensated) is connectedThe voltage is applied to the inverting input of operational amplifier A2 through operational amplifier A3, thus forming a closed-loop feedback having the voltage V at voltage node 10Net10＝VNet11＝VNet1V2, the excitation voltage signal of the quartz crystal X1 to be capacitively compensated can thus be controlled by regulating the voltage V2. The single-pole double-throw switch S1 and the double-pole double-throw switch S2 are used for switching selection of resistors so as to ensure the optimal magnification of the quartz crystal X1 to be compensated by capacitance. VNet11Is the voltage of node 11, VNet1Is the voltage of node 1. The optimal magnification is 1 to 6 times.
The static capacitance compensation unit includes: an operational amplifier A1, an operational amplifier A5, a resistor R10, a resistor R11, a capacitor C1 and a varactor diode D1; the inverting input end of the operational amplifier A1 is connected with the output end of the operational amplifier A1 and the non-inverting input end of the operational amplifier A5, the inverting input end of the operational amplifier A5 is connected to the ground through a resistor R10, the inverting input end of the operational amplifier A5 is also connected with one end of a capacitor C1 and the output end of the operational amplifier A5 through a resistor R11, the other end of the capacitor C1 is connected with the negative electrode of a variable-capacitance diode D1, and the positive electrode of the variable-capacitance diode D1 is connected with one end of a quartz crystal X1 to be capacitance-compensated; the direct current control unit includes: an operational amplifier A6, a direct current source V1, a resistor R12 and an inductor L1; the negative electrode of the direct current source V1 is connected to the ground, the positive electrode of the direct current source V1 is connected with the non-inverting input end of the operational amplifier A6, the inverting input end of the operational amplifier A6 is connected with the output end of the operational amplifier A6 and one end of the resistor R12, and the other end of the resistor R12 is connected with the negative electrode of the varactor D1 through the inductor L1;
as shown in fig. 3, which shows the amplitude-frequency characteristic curve of the quartz crystal near the resonant frequency when it is unloaded, in an ideal case, when the crystal with small static capacitance is in series resonance, the impedance is at a minimum and the phase is at zero. In fact, the quartz crystal X1 to be capacitance compensated can be equivalent to RLC series-parallel circuit (R) as shown in FIG. 2 when in operationq、Lq、CqAfter concatenation with C0In parallel). When static capacitance C0Very small, the current flowing through it is negligible and therefore has little effect on the series resonance. When connected in series, it is equivalent to electricityResistance RqWhen it becomes large, if the static capacitance C0Also becomes large and flows through the static capacitance C0Will have a non-negligible effect on the series resonant branch and therefore the static capacitance C needs to be set0To compensate. In the circuit of the static capacitance compensation unit, the potential V is applied to the quartz crystal X1 to be capacitance compensatedNet10V2, i.e. the potential applied to the static capacitance is V2, in order to compensate the static capacitance C0It is necessary to add a branch circuit to make the generated current be completely supplied to the static capacitor C0Therefore, the working current will completely flow through the series resonance branch circuit to make the static capacitor C0It has no influence on it. Specifically, an operational amplifier a5 forms a non-inverting amplifier, R10 is R11, and an input V of the operational amplifier a5 is VNet1Since V2 and C1 are dc blocking capacitors, VNet23＝VNet22＝2*V Net12 × V2. The voltage applied to the two ends of the variable capacitance diode D1 has the same phase and the difference is V2, and the capacitance of the variable capacitance diode D1 and the static capacitance C are adjusted at the moment0Equal, they cancel each other. The method for changing the capacitance of the varactor diode D1 is that a signal source V1 is an adjustable DC voltage source, and is applied to the negative electrode of the varactor diode D1 through an AC isolation resistor R12 and an inductor L1 by an operational amplifier A6. The working state after compensation is determined by the series branch, no matter how the load changes, the static capacitor C0And the crystal is always in a complete compensation state, and the crystal resonance is not influenced.
The signal attenuation unit includes: an operational amplifier A4, a single-pole double-throw switch S3, a double-pole double-throw switch S4, a resistor R5, a resistor R6, a resistor R7, a resistor R8 and a resistor R9; the non-inverting input end of the operational amplifier A4 is connected with the output end of the operational amplifier A2, the inverting input end of the operational amplifier A4 is connected with the output end of the operational amplifier A4, the inverting input end of the operational amplifier A4 is also connected with the moving end of the single-pole double-throw switch S3 through a resistor R5, the first and second moving ends of the single-pole double-throw switch S3 are respectively connected with the first and second moving ends of the double-pole double-throw switch S4, and the first, second, third and fourth moving ends of the double-pole double-throw switch S4 are respectively connected to the ground through a resistor R6, a resistor R7, a resistor R8 and a resistor R9;
in the circuit of the signal attenuation unit, the operational amplifier A4 is used for signal isolation, and V is providedNet12＝VNet6. The single-pole double-throw switch S3, the double-pole double-throw switch S4 and the resistors R5, R6, R7, R8 and R9 perform signal attenuation so that the voltages input into the analog multipliers A7 and A8 are in proper measurement ranges. Voltage node VNet15Expression for relation with signal source V2
Figure GDA0002885434240000071
Where A and ω are the amplitude and angular frequency of the signal source V2, and an analog multiplier A7 multiplies the signal VNet15Mixing with V3, analog multiplier A8 converts signal VNet15Mixing with V2, and calculating by the product and difference formula, the low pass filters LP1, LP2 can filter out the high frequency component with angular frequency of 2 omega in the mixed signal, wherein the DC quantity of the mixed signal is collected by the analog-to-digital converter ADC1 and ADC2 respectively
Figure GDA0002885434240000081
Where β is a scaling factor associated with the attenuation circuit and the amplification circuit. Whereby a voltage node V is obtainedNet6Amplitude-frequency characteristic of
Figure GDA0002885434240000082
Phase frequency characteristic
Figure GDA0002885434240000083
The signal acquisition unit includes: an analog multiplier a7, an analog multiplier A8, a low-pass filtering module LP1, a low-pass filtering module LP2, an analog-to-digital converter ADC1 and an analog-to-digital converter ADC 2; the cathode of the signal source V3 is connected to ground, the anode of the signal source V3 is connected to the second input terminal (Y) of the analog multiplier a7, the output terminal of the analog multiplier a7 is connected to the analog-to-digital converter ADC1 through the low-pass filtering module LP1, the cathode of the signal source V2 is connected to ground, the anode of the signal source V2 is connected to the second input terminal (Y) of the analog multiplier A8, the output terminal of the analog multiplier A8 is connected to the analog-to-digital converter ADC2 through the low-pass filtering module LP2, and the first input terminals of the analog multiplier a7 and the analog multiplier A8(X) are both connected to one end of the resistor R5.
In the present embodiment, the signal source V2 is a cosine signal, the signal source V3 is a sine signal, and the signal source V1 is a dc source.
The static capacitance compensation method of the static capacitance compensation circuit of the quartz crystal microbalance comprises the following steps:
s1, setting the single-pole double-throw switch S3 and the double-pole double-throw switch S4 to be attenuation maximum values, and setting the single-pole double-throw switch S1 and the double-pole double-throw switch S2 to be amplification minimum values; the single-pole double-throw switch S3 and the double-pole double-throw switch S4 are set to be attenuation maximum values so as to prevent the analog multiplier A7 and the analog multiplier A8 from exceeding the input range; the single-pole double-throw switch S1 and the double-pole double-throw switch S2 are set to the minimum amplification factor; so as to prevent the operational amplifier A2 from being distorted beyond the range;
s2, outputting the maximum voltage from the signal source V1, and using the signal source V1 as a direct current signal source; the compensation value is minimum at this moment;
s3, adjusting the frequency of the output signals of the signal source V2 and the signal source V3 to enable the frequency of the output signals of the signal source V2 and the signal source V3 to be close to the resonance frequency of the quartz crystal X1 to be capacitance compensated, wherein the signal source V2 and the signal source V3 are orthogonal waves with equal frequency, equal amplitude and 90-degree phase difference;
s4, collecting the voltage through ADC1 and ADC2 to obtain voltage VNet6Amplitude-frequency characteristics and phase-frequency characteristics of;
s5, according to the voltage VNet6The single-pole double-throw switch S1, the double-pole double-throw switch S2, the single-pole double-throw switch S3 and the double-pole double-throw switch S4 are switched according to the amplitude-frequency characteristic and the phase-frequency characteristic, so that the amplification factor of a quartz crystal X1 to be subjected to capacitance compensation reaches a preset multiple, and the input amplitude of an analog multiplier A7 and an analog multiplier A8 reaches a preset amplitude; the recorded frequency offset difference; wherein the frequency offset difference is the voltage V output by the operational amplifier A2Net6The frequency corresponding to the maximum amplitude value and the voltage V output by the operational amplifier A2Net6Corresponding to phase zeroA difference in frequency; the input amplitudes of the analog multiplier A7 and the analog multiplier A8 reach a preset amplitude and do not exceed 1V.
S6, sequentially reducing the output of the signal source V1 and changing the compensation value of the variable capacitance diode; and (5) repeating the steps 3, 4 and 5 until the signal source V1 outputs the lower limit value of the preset voltage, recording all frequency deviation differences, and searching the output voltage of the signal source V1 corresponding to the minimum frequency deviation difference as a static capacitance compensation voltage value point.
Comparing the experimental result of the liquid phase without capacitance compensation with the experimental result after capacitance compensation, the amplitude-frequency phase-frequency characteristic curve of the quartz crystal X1 before capacitance compensation in the liquid phase is shown in fig. 4 (a). The amplitude-frequency-phase-frequency characteristic curve of the quartz crystal X1 after capacitance compensation in the liquid phase is shown in FIG. 4 (b).
Experimental data
The static capacitance compensation circuit of the quartz crystal microbalance is utilized to test the static capacitance compensation precision of the quartz crystal microbalance, wherein a 1K resistor level is selected as a single-pole double-throw switch S1 and a double-pole double-throw switch S2, and test capacitors with the precision of 5% of 12PF, 18PF, 22PF and 27pF are respectively connected in parallel with the 1K resistor to form a test network.
The specific operation steps are as follows:
1. the single-pole double-throw switch S3 and the double-pole double-throw switch S4 are set to be in a non-attenuation state;
2. the single-pole double-throw switch S1 and the double-pole double-throw switch S2 are set to be 1K resistance gear;
3. connecting a 12PF capacitor and a 1K resistor into a test point Net 10;
4. the maximum value output by the direct current signal source V1 is applied to the variable capacitance diode D1, and the compensation value is minimum at the moment;
5. the control signal source V2, V3 generates orthogonal waves with the frequency of 10 MHz;
6. the analog multiplier A7 and the analog multiplier A8 acquire VNet6Amplitude and phase of;
7. reducing the output of the direct current signal source V1, and changing the compensation value of the variable capacitance diode D1;
8. repeating the step 4, the step 5, the step 6 and the step 7 to obtain an amplitude value and a phase curve related to the compensation capacitance value, and finding out the capacitance value corresponding to the zero phase as the compensated capacitance value;
9. changing the capacitance value of the test capacitor, and repeating the steps 5, 6, 7 and 8;
the compensated capacitance values were compared to the experimental results of the test capacitance values, and the results are shown in fig. 5: the points marked with triangles are the capacitance values tested, the points marked with squares are the capacitance values actually compensated, and the points marked with circles are the error values compensated.
In summary, a varactor diode is added in the circuit, the capacitance of the varactor diode is controlled by a direct current control unit, and an alternating voltage is applied to the varactor diode to ensure that the current passing through the varactor diode is equal to the current flowing through a quartz crystal static capacitor in magnitude and offset with each other, so as to achieve the purpose of capacitance compensation; the operational amplifier and the variable capacitance diode form a capacitance compensation unit for accurately compensating the static capacitance of the quartz crystal. The capacitance compensation range is as follows: 2pF-30pF, and capacitance compensation precision +/-2 pF. The invention is applicable to the occasions that the static capacitance in the quartz crystal microbalance cannot ignore the experimental measurement result, such as the situation that the viscoelasticity of the coating material on the surface of the crystal electrode is larger or the electrode is in the liquid phase, and all the situations that the static capacitance causes the overlarge equivalent resistance needs to be compensated.
The above-mentioned embodiments are preferred embodiments of the present invention, and the present invention is not limited thereto, and any other modifications or equivalent substitutions that do not depart from the technical spirit of the present invention are included in the scope of the present invention.

Claims (2)

1. A static capacitance compensation circuit for a quartz crystal microbalance, comprising: the device comprises a potential control unit, a direct current control unit, a static capacitance compensation unit, a signal attenuation unit and a signal acquisition unit;
the potential control unit includes: an operational amplifier A1, an operational amplifier A2, an operational amplifier A3, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a single-pole double-throw switch S1, a double-pole double-throw switch S2 and a quartz crystal X1 to be capacitance-compensated; the positive pole of a signal source V2 is connected with the non-inverting input end of an operational amplifier A1, the output end of the operational amplifier A1 is connected with the non-inverting input end of an operational amplifier A2, the output end of the operational amplifier A2 is connected with the first fixed end of a double-pole double-throw switch S2 through a resistor R1, the output end of the operational amplifier A2 is further connected with the second fixed end of the double-pole double-throw switch S2 through a resistor R2, the output end of the operational amplifier A2 is further connected with the third fixed end of the double-pole double-throw switch S2 through a resistor R3, the output end of the operational amplifier A2 is further connected with the fourth fixed end of the double-pole double-throw switch S2 through a resistor R4, the first fixed end of the double-pole double-throw switch S2 is connected with the first fixed end of the single-pole double-throw switch S1, the second fixed end of the double-pole double-throw switch S2 is connected with the second fixed end of the single-pole double-throw switch S5, the second fixed end of the single-pole double-throw switch S5857324 is, the other end of the quartz crystal X1 to be capacitance compensated is connected to the ground; one end of the quartz crystal X1 to be capacitance compensated is also connected with the non-inverting input end of the operational amplifier A3, and the inverting input end and the output end of the operational amplifier A3 are both connected with the inverting input end of the operational amplifier A2;
the static capacitance compensation unit includes: an operational amplifier A1, an operational amplifier A5, a resistor R10, a resistor R11, a capacitor C1 and a varactor diode D1; the inverting input end of the operational amplifier A1 is connected with the output end of the operational amplifier A1 and the non-inverting input end of the operational amplifier A5, the inverting input end of the operational amplifier A5 is connected to the ground through a resistor R10, the inverting input end of the operational amplifier A5 is also connected with one end of a capacitor C1 and the output end of the operational amplifier A5 through a resistor R11, the other end of the capacitor C1 is connected with the negative electrode of a variable-capacitance diode D1, and the positive electrode of the variable-capacitance diode D1 is connected with one end of a quartz crystal X1 to be capacitance-compensated;
the direct current control unit includes: an operational amplifier A6, a direct current source V1, a resistor R12 and an inductor L1; the negative electrode of the direct current source V1 is connected to the ground, the positive electrode of the direct current source V1 is connected with the non-inverting input end of the operational amplifier A6, the inverting input end of the operational amplifier A6 is connected with the output end of the operational amplifier A6 and one end of the resistor R12, and the other end of the resistor R12 is connected with the negative electrode of the varactor D1 through the inductor L1;
the signal attenuation unit includes: an operational amplifier A4, a single-pole double-throw switch S3, a double-pole double-throw switch S4, a resistor R5, a resistor R6, a resistor R7, a resistor R8 and a resistor R9; the non-inverting input end of the operational amplifier A4 is connected with the output end of the operational amplifier A2, the inverting input end of the operational amplifier A4 is connected with the output end of the operational amplifier A4, the inverting input end of the operational amplifier A4 is also connected with the moving end of the single-pole double-throw switch S3 through a resistor R5, the first and second moving ends of the single-pole double-throw switch S3 are respectively connected with the first and second moving ends of the double-pole double-throw switch S4, and the first, second, third and fourth moving ends of the double-pole double-throw switch S4 are respectively connected to the ground through a resistor R6, a resistor R7, a resistor R8 and a resistor R9;
the signal acquisition unit includes: an analog multiplier a7, an analog multiplier A8, a low-pass filtering module LP1, a low-pass filtering module LP2, an analog-to-digital converter ADC1 and an analog-to-digital converter ADC 2; the negative pole of the signal source V3 is connected to the ground, the positive pole of the signal source V3 is connected to the second input terminal of the analog multiplier A7, the output terminal of the analog multiplier A7 is connected to the analog-to-digital converter ADC1 through the low-pass filtering module LP1, the negative pole of the signal source V2 is connected to the ground, the positive pole of the signal source V2 is connected to the second input terminal of the analog multiplier a8, the output terminal of the analog multiplier a8 is connected to the analog-to-digital converter ADC2 through the low-pass filtering module LP2, and the first input terminal of the analog multiplier A7 and the first input terminal of the analog multiplier a8 are both connected to one;
the static capacitance compensation method of the static capacitance compensation circuit of the quartz crystal microbalance comprises the following steps:
s1, setting the single-pole double-throw switch S3 and the double-pole double-throw switch S4 to be attenuation maximum values, and setting the single-pole double-throw switch S1 and the double-pole double-throw switch S2 to be amplification minimum values;
s2, outputting the maximum voltage from the signal source V1, wherein the signal source V1 is a direct current signal source;
s3, adjusting the frequency of the output signals of the signal source V2 and the signal source V3 to enable the frequency of the output signals of the signal source V2 and the signal source V3 to be close to the resonance frequency of the quartz crystal X1 to be capacitance compensated, wherein the signal source V2 and the signal source V3 are orthogonal waves with equal frequency, equal amplitude and 90-degree phase difference;
s4, collecting the voltage through ADC1 and ADC2 to obtain voltage VNet6Amplitude-frequency characteristics and phase-frequency characteristics of;
s5, according to the voltage VNet6The single-pole double-throw switch S1, the double-pole double-throw switch S2, the single-pole double-throw switch S3 and the double-pole double-throw switch S4 are switched according to the amplitude-frequency characteristic and the phase-frequency characteristic, so that the amplification factor of a quartz crystal X1 to be subjected to capacitance compensation reaches a preset multiple, and the input amplitude of an analog multiplier A7 and an analog multiplier A8 reaches a preset amplitude; recording the offset difference of the frequency; wherein the frequency offset difference is the voltage V output by the operational amplifier A2Net6The frequency corresponding to the maximum amplitude value and the voltage V output by the operational amplifier A2Net6The difference in frequency corresponding to the phase zero;
s6, sequentially reducing the output of the signal source V1 and changing the compensation value of the variable capacitance diode; and (5) repeating the steps 3, 4 and 5 until the signal source V1 outputs the lower limit value of the preset voltage, recording all frequency deviation differences, and searching the output voltage of the signal source V1 corresponding to the minimum frequency deviation difference as a static capacitance compensation voltage value point.
2. The static capacitance compensation circuit of the quartz crystal microbalance of claim 1, wherein the signal source V2 is a cosine signal, the signal source V3 is a sine signal, and the signal source V1 is a dc source.
CN201910653127.6A 2019-07-19 2019-07-19 Static capacitance compensation circuit and method of quartz crystal microbalance Active CN110440883B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201910653127.6A CN110440883B (en) 2019-07-19 2019-07-19 Static capacitance compensation circuit and method of quartz crystal microbalance

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201910653127.6A CN110440883B (en) 2019-07-19 2019-07-19 Static capacitance compensation circuit and method of quartz crystal microbalance

Publications (2)

Publication Number Publication Date
CN110440883A CN110440883A (en) 2019-11-12
CN110440883B true CN110440883B (en) 2021-04-02

Family

ID=68430780

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201910653127.6A Active CN110440883B (en) 2019-07-19 2019-07-19 Static capacitance compensation circuit and method of quartz crystal microbalance

Country Status (1)

Country Link
CN (1) CN110440883B (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111835286B (en) * 2020-07-27 2024-02-02 中国电子科技集团公司第十三研究所 Crystal static capacitance offset circuit
CN112815819B (en) * 2020-12-31 2022-12-30 大族激光科技产业集团股份有限公司 Distance measuring device with temperature compensation function and cutting system

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106969815A (en) * 2017-03-20 2017-07-21 苏州康磁医疗科技有限公司 QCM plated film crystal-vibration-chip shunt capacitance is offset and indicating circuit

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4072912A (en) * 1976-11-12 1978-02-07 Rca Corporation Network for temperature compensation of an AT cut quartz crystal oscillator
US5185585A (en) * 1990-05-30 1993-02-09 New Sd, Inc. Crystal oscillator and method with amplitude and phase control
US5428319A (en) * 1993-11-29 1995-06-27 Motorola, Inc. Method and apparatus for providing a modified temperature compensation signal in a TCXO circuit
US10284143B2 (en) * 2002-03-06 2019-05-07 Piedek Technical Laboratory Quartz crystal unit, quartz crystal oscillator and electronic apparatus
JP2003324319A (en) * 2002-05-01 2003-11-14 Risotetsuku Japan Kk Electronic circuit
JP4361500B2 (en) * 2005-01-27 2009-11-11 パナソニック株式会社 Voltage controlled oscillator
JP4978134B2 (en) * 2006-09-28 2012-07-18 ミツミ電機株式会社 Voltage controlled oscillator
CN103973225B (en) * 2014-05-21 2017-10-27 北京遥测技术研究所 A kind of high impedance crystal resonator serial oscillation circuit and its adjustment method
CN204439093U (en) * 2015-03-06 2015-07-01 北京芯动联科微电子技术有限公司 For the self-calibrating device of the detecting electrode direct capacitance in gyroscope system
CN106603011B (en) * 2016-12-09 2019-12-27 电子科技大学 Voltage-controlled temperature compensation crystal oscillator
CN206649083U (en) * 2017-03-03 2017-11-17 深圳市沃特沃德股份有限公司 crystal oscillator equivalent negative resistance tester
CN106992668B (en) * 2017-03-27 2019-05-17 唐山航博电子科技有限公司 A kind of alternating current-direct current Mixed design DC power supply

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106969815A (en) * 2017-03-20 2017-07-21 苏州康磁医疗科技有限公司 QCM plated film crystal-vibration-chip shunt capacitance is offset and indicating circuit

Also Published As

Publication number Publication date
CN110440883A (en) 2019-11-12

Similar Documents

Publication Publication Date Title
CN110440883B (en) Static capacitance compensation circuit and method of quartz crystal microbalance
US5416448A (en) Oscillator circuit for use with high loss quartz resonator sensors
US20150226556A1 (en) Drive circuit for a mems resonator
Tangsrirat et al. Resistorless realization of current-mode first-order allpass filter using current differencing transconductance amplifiers
US9013234B2 (en) Transconductance adjustment circuit, circuit device, and electronic apparatus
EP2725368A2 (en) Impedance source ranging apparatus and method
CN110224689B (en) Oscillation starting circuit
Jakoby et al. Novel analog readout electronics for microacoustic thickness shear-mode sensors
Lamy et al. A new method for ohmic-drop compensation in potentiostatic circuits: Stability and bandpass analysis, including the effect of faradaic impedance
JP3135867B2 (en) Method for measuring CI of crystal unit and crystal oscillation circuit
RU2450416C1 (en) Quartz crystal oscillator
CN106330134B (en) A kind of crystal-oscillator circuit and its tuning methods
US6624708B1 (en) Active shunt capacitance cancelling oscillator circuit
KR101851967B1 (en) Capacitor-registor bank apparatus for evaluating capacitance bridge
JPH03254507A (en) Voltage control oscillator
Riesch et al. Novel readout electronics for thickness shear-mode liquid sensors compensating for spurious conductivity and capacitances
US20030098745A1 (en) Phase-locked loop oscillator with loop gain compensation
CN108333407B (en) Wide-frequency-range analog-digital mixed self-balancing bridge
RU2707394C2 (en) Generator
Ferrari et al. ACC oscillator for in-liquid quartz microbalance sensors
Biolek et al. Digitally-controlled quadrature oscillators employing modified CDBAs
JP2003324319A (en) Electronic circuit
Arnau et al. Improved electronic interfaces for heavy loaded AT cut quartz crystal microbalance sensors
JP3794018B2 (en) Attenuator frequency characteristics adjustment circuit
Laojum et al. Designed and Practiced a Voltage-mode Sinusoidal Oscillator using Commercially Available ICs.

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant