A high-load QCM driving circuit and quality detection device

Abstract

The utility model relates to a high-load QCM driving circuit and quality detection device. The QCM driving circuit includes: a transistor, a first resistor, a second resistor, a first capacitor, a second capacitor, a third resistor, a fourth resistor and a third capacitor; the base of the transistor is externally connected to a QCM crystal oscillator, the collector is connected to a power supply, and the emitter is grounded through the first resistor; the second resistor is connected across the collector and the base of the transistor; the first capacitor is connected across the base and the emitter of the transistor; the two ends of the second capacitor are respectively connected to the two ends of the first resistor; the third resistor and the fourth resistor are connected in series in sequence between the power supply and the ground; the connection point between the third resistor and the fourth resistor is connected to the emitter of the transistor through the third capacitor; the connection point between the third resistor and the fourth resistor is the first oscillation signal output end. The maximum load that can be driven by the utility model is relatively high.

Description

Technical Field

[0001] The utility model relates to the field of quartz crystal microbalance, in particular to a high-load driving circuit of a quartz crystal microbalance. Background Art

[0002] The Quartz Crystal Microbalance (QCM) is a sensitive mass detection instrument with a measurement accuracy of nanograms. The principle of the quartz crystal microbalance to detect mass is as follows: quartz crystal has the characteristics of piezoelectric effect and piezoelectric resonance; when an alternating voltage is applied to both ends of the quartz crystal, the quartz crystal will vibrate mechanically and generate an alternating electric field. Under normal circumstances, the amplitude of the mechanical vibration and alternating electric field generated by the quartz crystal is small; when the applied alternating voltage is equal to the resonant frequency, the amplitude of the mechanical vibration and alternating electric field generated by the quartz crystal becomes significantly larger. The value of the resonant frequency is related to the mass attached to the surface of the quartz crystal. Therefore, by collecting the oscillation signal, the resonant frequency can be inferred, and then the mass can be inferred.

[0003] The driving circuit of the quartz crystal microbalance provides an alternating excitation signal to the quartz crystal, forms a resonant circuit with the quartz crystal, and amplifies the oscillation signal.

[0004] The driving circuit of the quartz crystal microbalance in the prior art is usually a Pierce circuit, which has the defects of weak anti-interference ability and small load capacity. Utility Model Content

[0005] Based on this, the purpose of the utility model is to provide a high-load driving circuit for a quartz crystal microbalance, which has stronger anti-interference ability and higher load capacity than the existing Pierce circuit.

[0006] The utility model provides a high-load QCM driving circuit, comprising: a triode, a first resistor, a second resistor, a first capacitor, a second capacitor, a third resistor, a fourth resistor and a third capacitor; the base of the triode is externally connected to a QCM crystal oscillator, the collector is connected to a power supply, and the emitter is grounded through the first resistor; the second resistor is bridged between the collector and the base of the triode; the first capacitor is bridged between the base and the emitter of the triode; the two ends of the second capacitor are respectively connected to the two ends of the first resistor; the third resistor and the fourth resistor are connected in series in sequence between the power supply and the ground; the connection point between the third resistor and the fourth resistor is connected to the emitter of the triode through the third capacitor; the connection point between the third resistor and the fourth resistor is a first oscillation signal output end.

[0007] Compared with the existing Pierce circuit, the load capacity that can be driven by the high-load QCM driving circuit of the utility model and the amplitude of the generated oscillation signal are greatly improved, and the anti-interference ability to external interference signals is also enhanced.

[0008] Furthermore, it also includes a first inductor and a second inductor; the collector of the transistor is connected to the power supply through the first inductor; and the third resistor is connected to the power supply through the second inductor.

[0009] Furthermore, it also includes a waveform conversion module for converting a sine wave signal into a square wave signal; the input end of the waveform conversion module is connected to the first oscillation signal output end, and the output end is the second oscillation signal output end.

[0010] Furthermore, the waveform conversion module specifically includes a crystal oscillator chip and a fifth resistor; the first input end of the crystal oscillator chip is connected to the first oscillation signal output end, and the output end is connected to the second oscillation signal output end through the fifth resistor.

[0011] Furthermore, the model of the crystal oscillator chip is SN74LVC1GX04DBVR.

[0012] Furthermore, the model of the transistor is S9018.

[0013] Based on the same inventive concept, the utility model also provides a high-load QCM mass detection device, including a QCM crystal oscillator, any one of the above-mentioned high-load QCM drive circuits, and a post-stage processing module; the QCM crystal oscillator is connected to the QCM drive circuit; the QCM drive circuit outputs an oscillation signal to the post-stage processing module; the post-stage processing module calculates the mass of the substance to be detected according to the oscillation signal output by the QCM drive circuit.

[0014] Furthermore, the post-processing module is a single chip microcomputer.

[0015] In order to better understand and implement the present invention, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a module schematic diagram of a high-load QCM quality detection device of the utility model;

[0017] Figure 2 This is a schematic structural diagram of a high-load QCM driving circuit according to Embodiment 1 of the present utility model;

[0018] Figure 3 This is a schematic structural diagram of a high-load QCM driving circuit according to Example 2 of the utility model. DETAILED DESCRIPTION

[0019] It should be clear that the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the embodiments of the present application.

[0020] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the embodiments of the present application. The singular forms of "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0021] When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the attached claims. In the description of the present application, it should be understood that the terms "first", "second", "third", etc. are only used to distinguish similar objects, and do not have to be used to describe a specific order or sequence, nor can they be understood as indicating or implying relative importance. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0022] It should be understood that the embodiments of the present application are not limited to the precise structures described above and shown in the drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the embodiments of the present application is limited only by the appended claims.

[0023] See also Figure 1 , Figure 1 The module schematic diagram of the high-load QCM quality detection device of the utility model. The high-load QCM quality detection device of the utility model comprises: a QCM crystal oscillator 1, a QCM drive circuit 2 and a post-processing module 3. Among them, the QCM drive circuit 2 is the high-load QCM drive circuit of the utility model. The substance to be detected is attached to the surface of the QCM crystal oscillator 1. The QCM crystal oscillator 1 is connected to the QCM drive circuit 2; the QCM crystal oscillator 1 and the QCM drive circuit 2 together form a resonant circuit to generate an oscillation signal. The QCM drive circuit 2 is connected to the post-processing module 3 and outputs an oscillation signal to the post-processing module 3. The post-processing module 3 calculates the mass of the substance to be detected by analyzing the frequency of the oscillation signal.

[0024] Example 1

[0025] See also Figure 2 , Figure 2 The schematic diagram of the structure of the high-load QCM driving circuit of the embodiment 1 of the utility model is shown in FIG. The QCM driving circuit 2 is connected to the QCM crystal oscillator 1 and includes: a transistor Q1, a first inductor L1, a first resistor R1, a second resistor R2, a first capacitor C1, a second capacitor C2, a second inductor L2, a third resistor R3, a fourth resistor R4 and a third capacitor C3.

[0026] The first end of the QCM crystal oscillator 1 is connected to the base of the transistor Q1 , and the second end is grounded GND.

[0027] The collector of the transistor Q1 is connected to the power supply VCC through the first inductor L1, and the emitter is connected to the ground GND through the first resistor R1. The second resistor R2 is connected between the collector and the base of the transistor Q1. The first capacitor C1 is connected between the base and the emitter of the transistor Q1. Both ends of the second capacitor C2 are connected to both ends of the first resistor R1.

[0028] The second inductor L2, the third resistor R3 and the fourth resistor R4 are connected in series between the power supply VCC and the ground GND in sequence. The connection point between the third resistor R3 and the fourth resistor R4 is connected to the emitter of the transistor Q1 through the third capacitor C3. The connection point between the third resistor R3 and the fourth resistor R4 is the first oscillation signal output terminal OUT1, which is connected to the post-processing module 3 outside the driving circuit.

[0029] In this embodiment, the first oscillation signal OUT1 is a sine wave signal. The post-processing module 3 can calculate the mass of the substance to be detected by analyzing the frequency of the first oscillation signal OUT1.

[0030] Those skilled in the art can adjust the inherent resonant frequency of the first oscillation signal OUT1 by adjusting the values ​​of the second resistor R2, the first capacitor C1 and the second capacitor C2; and adjust the quality factor of the driving circuit by adjusting the resistance value of the first resistor R1; and adjust the magnitude of the DC component in the first oscillation signal OUT1 by adjusting the resistance value ratio of the third resistor R3 and the fourth resistor R4. The first inductor L1 and the second inductor L2 play the role of isolating the DC power supply VCC from the alternating current. The third capacitor C3 plays the role of stabilizing the DC component.

[0031] Since the first inductor L1 and the second inductor L2 play a role in protecting the power supply VCC and have no direct relationship with forming a resonant circuit, in another embodiment of the utility model, the QCM driving circuit 2 may not include the first inductor L1 and the second inductor L2, that is, the collector of the transistor Q1 is directly connected to the power supply VCC, and the first end of the fourth resistor R4 is directly connected to the power supply VCC.

[0032] The high-load QCM driving circuit of Example 1 of the utility model has the following technical effects: 1. The load that the existing Pierce circuit can drive is relatively small, resulting in the maximum detection mass of the QCM mass detection device based on the Pierce circuit being only 70μg. Experiments have proved that the maximum detection mass of the high-load QCM mass detection device of the utility model can reach 200μg, indicating that the driving ability of the high-load QCM driving circuit of the utility model is greatly enhanced, and the load that it can drive is relatively large. 2. Under the same experimental conditions, the peak-to-peak value of the first oscillation signal generated by the existing Pierce circuit is only 101.60mV, while the peak-to-peak value of the first oscillation signal generated by the high-load QCM driving circuit of the utility model reaches 864.00mV. It can be seen that the high-load QCM driving circuit of the utility model has greatly improved anti-interference ability to external interference signals.

[0033] Example 2

[0034] See also Figure 3 , Figure 3 Schematic diagram of the structure of the high-load QCM driving circuit of Example 2 of the present invention. The high-load QCM driving circuit of Example 2 of the present invention is basically the same as Example 1, except that the high-load QCM driving circuit of Example 2 of the present invention further includes a waveform conversion module 21.

[0035] The input end of the waveform conversion module 21 is connected to the first oscillation signal output end OUT1 (ie, the connection point between the third resistor R3 and the fourth resistor R4), and the output end is the second oscillation signal output end OUT2, which is connected to the post-processing module 3 outside the driving circuit.

[0036] The waveform conversion module 21 converts the first oscillation signal OUT1 into a second oscillation signal OUT2, and outputs the second oscillation signal OUT2 to the post-processing module 3. The post-processing module 3 calculates the mass of the substance to be detected by analyzing the frequency of the second oscillation signal OUT2.

[0037] Furthermore, the first oscillation signal OUT1 is a sine wave signal, and the second oscillation signal OUT2 is a square wave signal. The reason why the sine wave signal is converted into a square wave signal is that the post-processing module 3 is usually a digital signal processing device such as a counter or a single-chip microcomputer. Converting the sine wave signal into a square wave signal is more conducive to the post-processing module 3 to analyze the frequency of the oscillation signal.

[0038] In this embodiment, the waveform conversion module 21 specifically includes: a crystal oscillator chip U1 and a fifth resistor R5. The model of the crystal oscillator chip U1 is SN74LVC1GX04DBVR, the first input terminal X1 of which is connected to the first oscillation signal output terminal OUT1, the output terminal Y is connected to the second oscillation signal output terminal OUT2 through the fifth resistor R5, the power supply terminal is connected to a 3V power supply, and the ground terminal is grounded.

[0039] In one embodiment, the transistor Q1 is of model S9018, and the power supply VCC is a +12V power supply.

[0040] The working principle and technical effect of the high-load QCM driving circuit in Example 2 of the utility model are the same as those in Example 1, and will not be repeated here.

[0041] The above-mentioned embodiments only express several implementation methods of the utility model, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the utility model patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the utility model, and the utility model is also intended to include these modifications and modifications.

Claims

1. A high-load QCM driving circuit, characterized in that: include: A transistor, a first resistor, a second resistor, a first capacitor, a second capacitor, a third resistor, a fourth resistor and a third capacitor; The base of the transistor is externally connected to a QCM crystal oscillator, the collector is connected to a power supply, and the emitter is grounded through the first resistor; The second resistor is connected between the collector and the base of the transistor; The first capacitor is connected between the base and the emitter of the transistor; Two ends of the second capacitor are respectively connected to two ends of the first resistor; The third resistor and the fourth resistor are connected in series between the power supply and the ground in sequence; The connection point between the third resistor and the fourth resistor is connected to the emitter of the transistor through the third capacitor; The connection point between the third resistor and the fourth resistor is the first oscillation signal output terminal.

2. The high-load QCM driving circuit according to claim 1, characterized in that: It also includes a first inductor and a second inductor; the collector of the transistor is connected to a power supply through the first inductor; and the third resistor is connected to a power supply through the second inductor.

3. The high-load QCM driving circuit according to claim 2, characterized in that: It also includes a waveform conversion module for converting a sine wave signal into a square wave signal; the input end of the waveform conversion module is connected to the first oscillation signal output end, and the output end is the second oscillation signal output end.

4. The high-load QCM driving circuit according to claim 3, characterized in that: The waveform conversion module specifically includes a crystal oscillator chip and a fifth resistor; the first input end of the crystal oscillator chip is connected to the first oscillation signal output end, and the output end is connected to the second oscillation signal output end through the fifth resistor.

5. The high-load QCM driving circuit according to claim 4, characterized in that: The model of the crystal oscillator chip is SN74LVC1GX04DBVR.

6. The high-load QCM driving circuit according to claim 5, characterized in that: The model of the transistor is S9018.

7. A high-load QCM quality detection device, characterized in that: It comprises a QCM crystal oscillator, a high-load QCM driving circuit as described in any one of claims 1 to 6, and a post-processing module; the QCM crystal oscillator is connected to the QCM driving circuit; the QCM driving circuit outputs an oscillation signal to the post-processing module; the post-processing module calculates the mass of the substance to be detected according to the oscillation signal output by the QCM driving circuit.

8. The high-load QCM quality detection device according to claim 7, characterized in that: The post-processing module is a single chip microcomputer.

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