Piezoelectric sensor
By introducing a charge compensation module and a charge discharge module into the piezoelectric sensor, the problem of charge leakage in static force measurement is solved, thereby achieving accuracy and stability in static force measurement, reducing power consumption, and optimizing signal quality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SHENZHEN XINJINGCHENG SENSING TECHNOLOGY CO LTD
- Filing Date
- 2025-06-04
- Publication Date
- 2026-04-28
AI Technical Summary
Existing piezoelectric sensors are difficult to measure accurately when measuring static force due to rapid charge leakage. They also suffer from limited low-frequency response, sensitivity to high-frequency noise, complex stability design, and high power consumption.
A charge compensation module is introduced to compensate the first voltage signal by generating a second voltage signal, thus maintaining the relative constancy of the charge. Combined with an operational amplifier and capacitor, high-precision charge-to-voltage conversion is achieved. Residual charge is processed through a charge discharge module, optimizing signal amplification and filtering characteristics.
It achieves relative charge stability during static force measurement, improves measurement accuracy and stability, reduces power consumption, reduces noise interference, and expands the dynamic range.
Smart Images
Figure CN224175880U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of electronic technology, and more particularly to a piezoelectric sensor. Background Technology
[0002] In related technologies, piezoelectric sensors have always been used for dynamic measurements, that is, measuring rapidly changing forces. When measuring static pressure, the output of the dynamic charge amplification circuit of a piezoelectric sensor attenuates due to rapid charge leakage, making it difficult to measure static pressure. With the increasing demand for applications involving static forces, there is an urgent need for a piezoelectric sensor capable of measuring static forces. Utility Model Content
[0003] To address the related technical problems, this application provides a piezoelectric sensor capable of measuring static force.
[0004] The technical solution of this application embodiment is implemented as follows:
[0005] This application provides a piezoelectric sensor, which includes: a conversion module, a first signal amplification module, and a charge compensation module; wherein...
[0006] The conversion module is used to receive the charge generated by the piezoelectric material, convert the charge into a first voltage signal, and output the first voltage signal.
[0007] The first signal amplification module is used to receive the first voltage signal, amplify the first voltage signal into a standard industrial signal, and output the standard industrial signal.
[0008] The charge compensation module is used to receive the first voltage signal, generate a second voltage signal based on the voltage of the first voltage signal, and output the second voltage signal to the input terminal of the first signal amplification module to realize automatic compensation for the leakage charge of the piezoelectric material.
[0009] In some embodiments, the conversion module includes: a first operational amplifier, the negative input terminal of the first operational amplifier being connected to the output terminal of the piezoelectric material, and a first capacitor being connected between the negative input terminal of the first operational amplifier and the output terminal of the first operational amplifier.
[0010] In some embodiments, the first signal amplification module includes: a second operational amplifier, wherein a sliding rheostat is connected to the positive input terminal of the second operational amplifier, and the sliding rheostat is used to adjust the standard industrial signal output by the second operational amplifier.
[0011] In some embodiments, the piezoelectric sensor further includes a second signal amplification module for further amplifying the first voltage signal;
[0012] The second signal amplification module includes a third operational amplifier, the negative input terminal of which is connected to the output terminal of the conversion module, and the output terminal of which is connected to the negative input terminal of the second operational amplifier.
[0013] In some embodiments, a second capacitor is connected between the negative input terminal and the output terminal of the third operational amplifier.
[0014] In some embodiments, a third capacitor is connected between the negative input terminal and the output terminal of the second operational amplifier.
[0015] In some embodiments, the charge compensation module includes: a fourth operational amplifier, the positive input terminal of which is connected to the output terminal of the conversion module via a fourth capacitor; and the negative input terminal of which is connected to the negative input terminal of the second operational amplifier.
[0016] In some embodiments, the piezoelectric sensor further includes a charge discharge module, which includes an optocoupler that is turned on when a first signal is received, so as to release residual charge to ground.
[0017] The emitter of the optocoupler is grounded, and the collector of the optocoupler is connected to the output terminal of the fourth operational amplifier.
[0018] In some embodiments, the charge discharge module includes a fifth operational amplifier;
[0019] The positive input terminal of the fifth operational amplifier is grounded, and the negative input terminal of the fifth operational amplifier is connected to the collector of the optocoupler, the output terminal of the fourth operational amplifier, and the output terminal of the fifth operational amplifier, respectively.
[0020] In some embodiments, the charge discharge module further includes a sixth operational amplifier, the negative input terminal of which is connected to one end of a fifth capacitor, and the other end of the fifth capacitor is connected to the output terminal of the fifth operational amplifier.
[0021] The piezoelectric sensor provided in this application includes: a conversion module, a first signal amplification module, and a charge compensation module. The conversion module receives the charge generated by the piezoelectric material, converts the charge into a first voltage signal, and outputs the first voltage signal. The first signal amplification module receives the first voltage signal, amplifies it into a standard industrial signal, and outputs the standard industrial signal. The charge compensation module receives the first voltage signal, generates a second voltage signal based on the voltage of the first voltage signal, and outputs the second voltage signal to the input terminal of the first signal amplification module to achieve automatic compensation for the amount of charge leaking from the piezoelectric material. The piezoelectric sensor provided in this application addresses the characteristic of charge leakage when traditional piezoelectric sensors detect static force by introducing a charge compensation function. When measuring static force, if the measured force does not change, the charge remains relatively constant, thereby completing static measurement. Attached Figure Description
[0022] Figure 1 This is a schematic diagram of the structure of a piezoelectric sensor provided in an embodiment of this application;
[0023] Figure 2 A schematic diagram of the circuit structure of a piezoelectric sensor provided as an application example of this application. Detailed Implementation
[0024] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.
[0025] It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application.
[0026] In related technologies, piezoelectric sensors have traditionally been used for dynamic measurements, specifically measuring rapidly changing forces, due to their operating principle. However, when measuring static pressure, the output of the dynamic charge amplification circuit in a piezoelectric sensor attenuates due to rapid charge leakage, making it difficult to measure static pressure. With the increasing demand for applications involving static forces, and given the advantages of piezoelectric sensors such as strong anti-interference capabilities and low sensitivity to sensor deformation under stress, there is a pressing need for a piezoelectric sensor capable of measuring static forces.
[0027] Furthermore, traditional piezoelectric sensors for measuring dynamic forces also have the following problems:
[0028] 1. Limited low-frequency response, unable to handle static or extremely low-frequency signals. The dynamic charge amplifier circuit in piezoelectric sensors typically employs AC coupling (such as series capacitors) or a short time constant design, which limits its low-frequency response. For example, the discharge time constant (DTC) of the dynamic charge amplifier circuit is short, making it unable to effectively integrate long-term continuous charge inputs. This characteristic makes it unsuitable for measuring static forces, slowly changing pressures, or DC signals.
[0029] 2. Sensitive to high-frequency noise, leading to a decrease in signal-to-noise ratio. Dynamic charge amplifier circuits typically require higher bandwidth to achieve high-frequency response, which can introduce more noise. For example, while chopper stabilization can reduce low-frequency noise, it introduces switching noise and charge injection effects. Especially in low-gain configurations, the folding effect of broadband voltage noise significantly increases input current noise. Furthermore, at high frequencies, thermal noise from resistors and shot noise within the amplifier are also exacerbated.
[0030] 3. Complex stability design requires additional compensation. The high-frequency response requirements of dynamic charge amplifier circuits may lead to insufficient phase margin, necessitating complex frequency compensation networks (such as lead-lag networks) to avoid oscillations. For example, in high-gain configurations, the open-loop gain of dynamic charge amplifier circuits decreases rapidly with frequency, easily causing stability issues.
[0031] 4. Higher power consumption limits application scenarios. Dynamic charge amplifier circuits typically require higher bias currents or more complex circuit structures to achieve high-frequency performance, leading to increased power consumption. For example, chopper-stabilized amplifiers require a clock signal drive, consuming additional power. In contrast, quasi-static circuits can reduce quiescent current through high-impedance feedback resistors, making them suitable for low-power applications.
[0032] 5. Dynamic range may be limited. The signal amplitude of a dynamic charge amplifier circuit in the high-frequency range may be limited by the amplifier slew rate or the power supply voltage, resulting in a reduced dynamic range. For example, when processing large signals, the output of the dynamic charge amplifier circuit may be distorted due to insufficient slew rate.
[0033] The piezoelectric sensors provided in various embodiments of this application introduce a charge compensation function to address the characteristic of charge leakage when traditional piezoelectric sensors detect static force. When measuring static force, the charge remains relatively constant when the measured force does not change, thereby completing the static measurement.
[0034] This application provides a piezoelectric sensor, such as... Figure 1 As shown, the piezoelectric sensor includes: a conversion module 101, a first signal amplification module 102, and a charge compensation module 103; wherein,
[0035] The conversion module 101 is used to receive the charge generated by the piezoelectric material, convert the charge into a first voltage signal, and output the first voltage signal.
[0036] The first signal amplification module 102 is used to receive the first voltage signal, amplify the first voltage signal into a standard industrial signal, and output the standard industrial signal.
[0037] The charge compensation module 103 is used to receive the first voltage signal, generate a second voltage signal based on the voltage of the first voltage signal, and output the second voltage signal to the input terminal of the first signal amplification module 102 to realize automatic compensation for the leakage charge of the piezoelectric material.
[0038] It is understood that the solution provided in this application addresses the characteristic of charge leakage when traditional piezoelectric sensors detect static force by introducing a charge compensation function. Specifically, after converting the charge generated by the piezoelectric material into a first voltage signal, the charge compensation module 103 acquires the first voltage signal and generates a second voltage signal for compensation. The second voltage signal is then used to compensate the input of the first signal amplification module 102, ultimately outputting a compensated standard industrial signal. When measuring static force, the lost charge is compensated back in the form of voltage, effectively maintaining the relative constancy of the charge, thus completing the static measurement. This static measurement can also be called quasi-static measurement because the piezoelectric sensor provided in this application still actually has charge leakage, but the solution in this circuit effectively slows down the charge leakage rate, thereby achieving the effect of measuring static force.
[0039] For example, when an object to be measured is placed on a piezoelectric sensor, the piezoelectric material generates an electric charge during the process from the moment the object touches the sensor until the object is completely stable. This charge can leak out rapidly, making it impossible for the piezoelectric sensor to accurately measure static force when the pressure is stable. The piezoelectric sensor provided in this application receives the charge generated by the piezoelectric material during the process from the moment the sensor is subjected to pressure until the pressure stabilizes. When measuring static force, that is, when the pressure is stable, the charge leaked during this process is compensated back in the form of voltage, which is equivalent to keeping the charge relatively unchanged, thereby completing the static measurement.
[0040] Considering the advantages of operational amplifiers in signal processing and the charging and discharging characteristics of capacitors, a capacitor is connected between the negative input terminal and the output terminal of the operational amplifier to achieve high-precision charge-to-voltage signal conversion.
[0041] Based on this, in some embodiments, the conversion module includes: a first operational amplifier, the negative input terminal of the first operational amplifier being connected to the output terminal of the piezoelectric material, and a first capacitor being connected between the negative input terminal of the first operational amplifier and the output terminal of the first operational amplifier.
[0042] In practical applications, when the piezoelectric material outputs charge, due to its "virtual break" characteristic, the charge flowing into the negative input terminal of the first operational amplifier cannot flow into ground or power supply through the internal circuit of the first operational amplifier. It must form a circuit through external components, meaning it can only charge and discharge the first capacitor connected between the negative input and output terminals. According to the characteristics of a capacitor, the relationship between the charge Q and the voltage V across the capacitor is Q = C × V (where C is the capacitance of the first capacitor). As the piezoelectric material generates charge and accumulates on the first capacitor, a corresponding voltage change occurs across the first capacitor. This voltage change is the output voltage signal. In this way, the input charge can be accurately converted into a corresponding voltage signal for output.
[0043] Here, the piezoelectric sensor requires a DC bias voltage before outputting a standard industrial signal to avoid a situation where the input is 0 but the output is not. Both the first operational amplifier and the first capacitor exhibit high impedance characteristics to DC signals, enabling the establishment and maintenance of a stable DC operating point and ensuring stable output from the piezoelectric sensor. Furthermore, the high-impedance feedback circuit has a weak shunting effect on common-mode signals, making it difficult for common-mode interference to form a loop through the feedback network, effectively suppressing common-mode interference. The high-impedance feedback circuit also reduces the quiescent current in the circuit; due to the lower quiescent current, the piezoelectric sensor consumes less power. In addition, the first capacitor enables the first operational amplifier to have low-pass filtering characteristics, narrowing the circuit bandwidth, making it easier to ensure measurement stability, and reducing the complexity of the circuit design.
[0044] To avoid zero-point drift in the piezoelectric sensor, i.e., non-zero output voltage when there is no input, a sliding rheostat is needed to provide an adjustable DC bias voltage to the amplifier, thereby adjusting the DC level of the output signal to meet the reference requirements of the industry standard.
[0045] Based on this, in some embodiments, the first signal amplification module includes: a second operational amplifier, wherein a sliding rheostat is connected to the positive input terminal of the second operational amplifier, and the sliding rheostat is used to adjust the standard industrial signal output by the second operational amplifier.
[0046] Here, the slider of the variable resistor divides the resistance into two parts. By adjusting the position of the slider, the resistance connected to the positive input terminal of the second operational amplifier can be changed, thereby adjusting the DC bias voltage at the positive input terminal. When the piezoelectric sensor has no input, adjusting the variable resistor makes the voltage output by the second operational amplifier equal to the zero point of the standard signal, which can cancel the zero-point drift of the sensor.
[0047] The first voltage signal output by the conversion module may still be weak, and the voltage amplification at one time is insufficient to meet the driving requirements of subsequent standard industrial signals (such as -10 to 10V), so further signal amplification is required.
[0048] Accordingly, in some embodiments, the piezoelectric sensor further includes a second signal amplification module for further amplifying the first voltage signal;
[0049] The second signal amplification module includes a third operational amplifier, the negative input terminal of which is connected to the output terminal of the conversion module, and the output terminal of which is connected to the negative input terminal of the second operational amplifier.
[0050] Here, the negative input terminal of the third operational amplifier receives the first voltage signal from the conversion module and outputs the amplified first voltage signal at the output terminal, which is then provided to the negative input terminal of the second operational amplifier.
[0051] The circuit is affected by mechanical vibration, electromagnetic environment, etc., and the signal may be coupled with high-frequency noise during transmission, resulting in the amplified voltage signal containing glitches or distortion. In order to optimize the signal amplification performance of the third operational amplifier, it is necessary to adjust the frequency response of the signal to improve the quality of signal amplification.
[0052] Therefore, in some embodiments, a second capacitor is connected between the negative input terminal and the output terminal of the third operational amplifier.
[0053] Here, a second capacitor is connected between the negative input terminal and the output terminal of the third operational amplifier, which enables the second signal amplification module to simultaneously possess low-pass filtering characteristics, suppressing high-frequency noise and making it suitable for high-precision measurement of low-frequency signals (signals of static force are usually low-frequency).
[0054] Piezoelectric signals are susceptible to high-frequency noise pollution, and the noise becomes significantly harmful after amplification. Therefore, it is necessary to introduce a capacitor in the feedback loop of the first signal amplification module to enhance the effect of low-pass filtering and improve signal quality.
[0055] Therefore, in some embodiments, a third capacitor is connected between the negative input terminal and the output terminal of the second operational amplifier.
[0056] Here, if the signal contains high-frequency interference, the third capacitor can attenuate the high-frequency signal, retain and amplify the low-frequency signal, making the output signal purer and improving the quality of the output standard industrial signal.
[0057] It should be noted that the first, second, and third capacitors attenuate high-frequency signals, resulting in a lower and narrower bandwidth for the static force measurement circuit of the piezoelectric sensor. This lower bandwidth reduces the requirement for high slew rate, allowing for a wider dynamic range, while the narrower bandwidth makes stability easier to ensure and reduces design complexity. In practical applications, the piezoelectric sensor provided in this application can achieve a response frequency of 30kHz when measuring dynamic force and 4-5kHz when measuring static force.
[0058] When piezoelectric materials are subjected to force for a long time, charge leakage will occur, causing the first voltage signal output by the conversion module to decay rapidly, which seriously affects the measurement accuracy of the sensor. The charge compensation module needs to compensate for the decay of the first voltage signal to achieve the accuracy and stability of static force measurement.
[0059] Based on this, in some embodiments, the charge compensation module includes: a fourth operational amplifier, the positive input terminal of which is connected to the output terminal of the conversion module through a fourth capacitor; and the negative input terminal of the fourth operational amplifier is connected to the negative input terminal of the second operational amplifier.
[0060] Here, for example, when an object to be measured is placed on a piezoelectric sensor, during the process from when the object just touches the sensor until the object is completely stable, the charge generated by the piezoelectric material will leak rapidly, causing the first voltage signal to produce an abrupt change similar to AC. The positive input terminal of the fourth operational amplifier detects the abrupt change in the first voltage signal through the fourth capacitor, and generates a second voltage signal based on the first voltage signal. The second voltage signal is then delayed and compensated to the negative input terminal of the second operational amplifier, thereby achieving the accuracy and stability of static force measurement.
[0061] The fourth capacitor utilizes its capacitive reactance to block DC, allowing only low-frequency AC error signals (the portion requiring compensation) to pass through, thus achieving precise compensation. Furthermore, based on the virtual short characteristic of operational amplifiers, the voltage at the negative input terminal of the fourth operational amplifier can track the voltage change at its positive input terminal in real time. Therefore, the negative input terminal of the fourth operational amplifier is used as the output port of the compensation voltage, connected to the negative input terminal of the second operational amplifier. This injects the voltage used for charge compensation into the input terminal of the first signal amplification module, offsetting charge loss caused by leakage and maintaining signal accuracy. This forms a closed-loop feedback control, achieving automatic charge compensation.
[0062] For example, in practical applications, the first voltage signal output by the conversion module is input to the positive input terminal of the fourth operational amplifier of the charge compensation module through the fourth capacitor. The fourth operational amplifier monitors the changes in the first voltage signal in real time. When charge leakage occurs in the piezoelectric material, the first voltage signal changes accordingly, causing the generated second voltage signal to follow the change in the first voltage signal. Here, the second voltage signal can be the same as or different from the first voltage signal. The fourth operational amplifier can be configured with a feedback network between its output terminal and negative input terminal to appropriately amplify the second voltage signal according to the compensation situation of the actual circuit. For example, during sensor debugging, if it is found that the second voltage signal, which is the same as the first voltage signal, is insufficient to compensate for the amount of leaked charge, the fourth operational amplifier can be configured with a feedback network to amplify the second voltage signal according to the amplification factor and output the amplified second voltage signal, thereby improving the accuracy of charge compensation and thus improving the accuracy of the piezoelectric sensor. The negative input terminal of the fourth operational amplifier is connected to the negative input terminal of the second operational amplifier, so that the second voltage signal can be fed back to the input terminal of the first signal amplification module to compensate for the signal deviation caused by charge leakage and maintain the accuracy of the output signal. The specific amplification factor can be determined based on actual needs such as the debugging of the piezoelectric sensor. This application does not limit the specific size of the amplification factor.
[0063] Here, when the sensor generates a negative charge during reverse recovery, the circuit cannot completely neutralize the compensated charge. Since the accumulation of residual charge in the circuit will interfere with normal signal transmission and affect the stability of the sensor, a special module needs to be designed to discharge the residual charge.
[0064] Based on this, in some embodiments, the piezoelectric sensor further includes a charge discharge module, which includes an optocoupler that is turned on when a first signal is received, so as to release the residual charge to ground;
[0065] The emitter of the optocoupler is grounded, and the collector of the optocoupler is connected to the output terminal of the fourth operational amplifier.
[0066] Here, when the optocoupler receives the first signal and turns on, the charge flows out through the emitter of the optocoupler, releasing the residual charge to ground and preventing the residual charge in the circuit from affecting the next measurement.
[0067] For example, in practical applications, when residual charge accumulates in the circuit after a measurement by the piezoelectric sensor, the optocoupler receives a zero signal (such as a low-level signal) and lights up the diode in the optocoupler, thus turning on the optocoupler. At this time, the emitter of the optocoupler is grounded, and the collector is connected to the output of the fourth operational amplifier, providing a path to ground for the residual charge in various parts of the circuit. Here, the zero signal can be sent by the user by switching an external switch, or it can be sent through the IO interface of the client (such as a computer). This application embodiment does not limit the specific method of obtaining the zero signal.
[0068] When the charge is discharged, the output of the fourth operational amplifier in the charge compensation module may generate a voltage in the volt range, which can easily flow back to the probe side of the piezoelectric sensor and cause damage to the sensor.
[0069] Accordingly, in some embodiments, the charge discharge module includes a fifth operational amplifier;
[0070] The positive input terminal of the fifth operational amplifier is grounded, and the negative input terminal of the fifth operational amplifier is connected to the collector of the optocoupler, the output terminal of the fourth operational amplifier, and the output terminal of the fifth operational amplifier, respectively.
[0071] Here, the function of the fifth operational amplifier is to configure the feedback network of the fifth operational amplifier to make the amplification factor less than 1, thereby reducing the voltage at the output terminal of the fourth operational amplifier and preventing excessive current from flowing back to the probe side of the piezoelectric sensor, which could damage the sensor.
[0072] When there is no external stress, the piezoelectric sensor has no charge input and theoretically does not generate new charge. However, if the input impedance of the circuit is low, leakage current will be formed through the internal resistance, causing the charge to leak rapidly and causing voltage fluctuations. This makes the output standard industrial signal prone to fluctuations (i.e., fluctuating between -10V and 10V).
[0073] Based on this, in some embodiments, the charge discharge module further includes a sixth operational amplifier, the negative input terminal of which is connected to one end of a fifth capacitor, and the other end of the fifth capacitor is connected to the output terminal of the fifth operational amplifier.
[0074] Here, connecting the sixth operational amplifier provides a path for leakage charge within the operational amplifier. Since the differential input resistance of the operational amplifier is very high, it consumes almost no charge from the sensor after connection, keeping the charge in the sensor approximately constant. This avoids voltage jumps caused by charge leakage, thus making the output standard industrial signal more stable.
[0075] In the embodiments of this application, the module is implemented by a circuit, chip, or device; therefore, the module can also be referred to as a circuit or device.
[0076] The piezoelectric sensor provided in this application includes: a conversion module, a first signal amplification module, and a charge compensation module. The conversion module receives the charge generated by the piezoelectric material, converts the charge into a first voltage signal, and outputs the first voltage signal. The first signal amplification module receives the first voltage signal, amplifies it into a standard industrial signal, and outputs the standard industrial signal. The charge compensation module receives the first voltage signal, amplifies it into a second voltage signal, and outputs the second voltage signal to the input terminal of the first signal amplification module to achieve automatic compensation for the amount of charge leaking from the piezoelectric material. The piezoelectric sensor provided in this application addresses the characteristic of charge leakage when traditional piezoelectric sensors detect static force by introducing a charge compensation function. When measuring static force, if the measured force does not change, the charge remains relatively constant, thereby completing the static measurement.
[0077] Based on the above embodiments, this application provides an application example of a piezoelectric sensor. For example... Figure 2 As shown, the piezoelectric sensor provided in the application example of this application includes: a conversion module, a first signal amplification module, a charge compensation module, a second signal amplification module, and a charge discharge module.
[0078] The conversion module includes: operational amplifier U1-A (i.e., the first operational amplifier mentioned above), resistor R23, and capacitor C12 (i.e., the first capacitor mentioned above); wherein, capacitor C12 can be 1nF, the negative input terminal of operational amplifier U1-A is connected to capacitor C12, the positive input terminal of operational amplifier U1-A is grounded through resistor R23, the positive power supply terminal of operational amplifier U1-A is connected to an 8V voltage, the negative power supply terminal is connected to a -8V voltage, and the other end of capacitor C12 is connected to the output terminal of operational amplifier U1-A.
[0079] like Figure 2 As shown, J2 is a coaxial line used to transmit the charge of the piezoelectric sensor. The charge enters from port 2 of J2, and the input speed of the charge is slowed down by resistor R14. The charge is input to the negative input terminal of operational amplifier U1-A. The charge at the negative input terminal of operational amplifier U1-A charges and discharges capacitor C12, and a corresponding voltage change is generated across capacitor C12. This voltage change is the first output voltage signal.
[0080] The first signal amplification module includes: operational amplifier U1-D (i.e., the second operational amplifier mentioned above), a sliding rheostat R36, resistors R32, R33, R22, R2, R11, and R17, and capacitor C8 (i.e., the third capacitor mentioned above); wherein, capacitor C8 can be 68pF. The positive input terminal of operational amplifier U1-D is connected to resistors R33 and R32 respectively. The other end of resistor R33 is grounded. The other end of resistor R32 is connected to the sliding rheostat R36. The negative input terminal of operational amplifier U1-D is connected to resistor R2, capacitor C8, and resistor R11 respectively. The other end of resistor R11 is connected to resistors R22 and R17 respectively. The output terminal of operational amplifier U1-D is connected to the other end of capacitor C8 and the other end of resistor R22 respectively. R17 is connected to the standard industrial signal output port U-out. One end of the sliding rheostat R36 is connected to a negative voltage of -8V, and the other end is connected to a positive voltage of 8V Vcc. TP2 is a test interface.
[0081] Here, the slider of the variable resistor divides the resistance into two parts. By adjusting the position of the slider, the resistance connected to the positive input terminal of the operational amplifier U1-D can be changed, thereby adjusting the DC bias voltage at the positive input terminal. When the piezoelectric sensor has no input, the variable resistor can be adjusted so that the voltage output by the operational amplifier U1-D is equal to the zero point of the standard industrial signal, which can cancel the zero-point drift of the sensor and make the output standard industrial signal more accurate.
[0082] The charge compensation module includes operational amplifier U4-A (i.e., the aforementioned fourth operational amplifier), resistors R25, R24, R18, R30, and R21, and capacitors C2, C5 (i.e., the aforementioned fourth capacitor), C7, and C9. The negative input terminal of operational amplifier U4-A is connected to capacitors C7, C9, C2, and R21, and the positive input terminal is connected to resistor R25 and capacitor C5. The other resistor is... One end of the capacitor is grounded. The other end of the capacitor C5 is connected to the output terminal of the operational amplifier U1-A. The positive power supply terminal of the operational amplifier U4-A is connected to an 8V voltage, and the negative power supply terminal of the operational amplifier U4-A is connected to an -8V voltage. The output terminal of the operational amplifier U4-A is connected to the other end of the capacitor C7 and the resistor R24. The other end of the resistor R24 is connected to the capacitor C9, the resistor R30, and the resistor R18. The other end of the resistor R18 is grounded. The other end of the resistor R30 is connected to the capacitor C2. The other end of the capacitor C2 is connected to the resistor R21. The other end of the resistor R21 is connected to the negative input terminal of the operational amplifier U1-D through the resistor R2.
[0083] Here, the first voltage signal output from the conversion module is input to the positive input terminal of the operational amplifier U4-A in the charge compensation module through capacitor C5. When the first voltage signal changes, the positive input terminal of operational amplifier U4-A detects the sudden change in the first voltage signal and generates a second voltage signal at the negative input terminal of operational amplifier U4-A based on the first voltage signal. This second voltage signal is then compensated at the negative input terminal of operational amplifier U1-D, achieving accuracy and stability in static force measurement. Furthermore, a feedback network composed of resistors R21, R30, and R24 can be used to amplify the second voltage signal. The amplified second voltage signal is then output to the negative input terminal of operational amplifier U1-D, improving the accuracy of charge compensation and thus enhancing the precision of the piezoelectric sensor.
[0084] In practical applications, when measuring static force, the sensor receives the charge generated by the piezoelectric material from the moment the pressure is applied until the pressure stabilizes, and converts it into a first voltage signal. The charge compensation module generates a second voltage signal based on the first voltage signal. The second voltage signal can compensate for the leakage charge in the form of voltage after receiving the first voltage signal, that is, when the pressure stabilizes, it compensates for the leakage charge in the form of voltage, thereby completing the static measurement. Capacitors C2, C9, and C7 are key components for achieving the delayed compensation of the voltage corresponding to the charge. Specifically, when the piezoelectric material generates charge instantaneously under pressure, capacitors C2, C9, and C7 charge rapidly, recording the voltage corresponding to the input charge from the moment the sensor is subjected to pressure until the pressure stabilizes. When capacitors C2, C9, and C7 discharge as energy storage elements, the voltage across them does not drop suddenly but decreases slowly over time, thus creating a delayed characteristic. Simultaneously, when charge is generated during the process from the moment the sensor is subjected to pressure until the pressure stabilizes, C2 in the RC integrator circuit charges rapidly and then discharges slowly with a time constant of τ = R30 × C2. Operational amplifier U4-A integrates this low-frequency voltage change through negative feedback and outputs a second voltage signal to continuously cancel the leakage voltage, ensuring the accuracy of static measurements.
[0085] The second signal amplification module includes: operational amplifier U1-C (i.e., the third operational amplifier mentioned above), capacitor C3 (i.e., the second capacitor mentioned above), resistor R12, and resistor R31; wherein, capacitor C3 can be 51pF, the output terminal of operational amplifier U1-C is connected to the negative input terminal of operational amplifier U1-C through capacitor C3, the positive input terminal of operational amplifier U1-C is grounded, the output terminal of operational amplifier U1-C is also connected to resistor R12, and the other end of R12 is connected to resistor R31 and the output terminal of operational amplifier U1-C respectively.
[0086] Here, the operational amplifier U1-C amplifies the first voltage signal in two stages according to the feedback network formed by resistors R31 and R12. Capacitor C3 enables the second signal amplification module to have low-pass filtering characteristics, which can suppress high-frequency noise and match the low-frequency operating characteristics of the piezoelectric sensor (the signal of static force is usually low frequency).
[0087] The charge discharge module includes: optocoupler U5, operational amplifier U1-B (i.e., the fifth operational amplifier mentioned above), operational amplifier U2-B (i.e., the sixth operational amplifier mentioned above), operational amplifier U2-A, resistors R35, R19, R29, R16, R15, R34, R13, R26, R27, and R28, and capacitors C11, C4, and C6. The collector of optocoupler U5 is connected to the output of operational amplifier U4-A through an RC circuit formed by resistor R19 and capacitor C11. The emitter of optocoupler U5 is grounded. The cathode of the diode of optocoupler U5 is connected to the port receiving the zero signal. The anode of the diode of optocoupler U5 is connected to an 8V voltage through resistor R35. The positive input terminal of operational amplifier U1-B is grounded, and the negative input terminal is connected to the RC circuit formed by resistor R19 and capacitor C11 through resistor R29. In the circuit, the negative input terminal of operational amplifier U1-B is connected to the output terminal of operational amplifier U1-B through resistor R16. The collector of optocoupler U5 is connected in sequence to resistors R27 and R28 and an 8V positive power supply voltage. The output terminal of operational amplifier U1-B is connected to capacitors C6 and C4 through resistor R15. The other end of capacitor C6 is connected to the negative input terminal of operational amplifier U1-A and resistor R34. The other end of resistor R34 is connected to the negative input terminal of operational amplifier U2-B. The other end of capacitor C4 is connected to resistors R27 and R13. The other end of resistor R27 is connected to resistor R28 and the positive power supply terminal of operational amplifier U2-A. The other end of resistor R28 is connected to an 8V power supply voltage. The other end of resistor R13 is connected to the negative power supply terminal of operational amplifier U2-A and resistor R26. The other end of resistor R26 is connected to a -8V negative voltage.
[0088] Here, after a measurement by the piezoelectric sensor, residual charge accumulates in the circuit. When optocoupler U5 receives a zero signal (such as a low-level signal), the diode in optocoupler U5 lights up, thus turning on optocoupler U5. At this time, the emitter of the optocoupler is grounded, and the collector is connected to the output of the fourth operational amplifier, providing a path to ground for the residual charge in various parts of the circuit. Simultaneously, operational amplifier U1-B, through the feedback network composed of resistors R29 and R16, configures the amplification factor to be less than 1, thereby reducing the output voltage of operational amplifier U4-A and preventing excessive current from flowing back to the probe side of the piezoelectric sensor, i.e., the source of the charge received by J2 (not shown in the figure), which could damage the sensor. The function of connecting operational amplifiers U2-B and U2-A is to provide a path for leakage charge within the operational amplifier, keeping the charge in the sensor approximately constant, thus avoiding voltage jumps caused by charge leakage and making the output standard industrial signal more stable.
[0089] Among them, the operational amplifiers U2-A and U2-B can be LMC662, and the other operational amplifiers can be LMC660. The model of each component and the specific capacitance and resistance values can be set according to actual needs. This application embodiment does not limit the resistance and capacitance values of the above circuit, as well as the specific models of each operational amplifier and optocoupler.
[0090] Based on the above description, the piezoelectric sensor provided in this application embodiment has the following beneficial effects:
[0091] 1. An automatic charge compensation circuit is introduced to address the charge leakage characteristics in static applications. In static applications, when the measured force value does not change, the charge remains relatively constant, thus completing the static measurement.
[0092] 2. Add a residual charge discharge function switch to solve the measurement repeatability error caused by residual charge.
[0093] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.
[0094] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the stated features. In the description of the embodiments of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. It should be noted that "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.
[0095] It should be understood that the phrase "some embodiments" throughout the specification means that a particular feature, structure, or characteristic related to an embodiment is included in at least one embodiment of this application. Therefore, "some embodiments" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments without conflict.
[0096] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" or "linked" should be interpreted broadly. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a connection that allows communication between the components; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.
[0097] The above description is merely a preferred embodiment of this application and is not intended to limit the scope of patent protection of this application. Any equivalent structural transformations made based on the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of this application.
Claims
1. A piezoelectric sensor, characterized in that, include: The module comprises a conversion module, a first signal amplification module, and a charge compensation module; among which, The conversion module is used to receive the charge generated by the piezoelectric material, convert the charge into a first voltage signal, and output the first voltage signal. The first signal amplification module is used to receive the first voltage signal, amplify the first voltage signal into a standard industrial signal, and output the standard industrial signal. The charge compensation module is used to receive the first voltage signal, generate a second voltage signal based on the voltage of the first voltage signal, and output the second voltage signal to the input terminal of the first signal amplification module to realize automatic compensation for the leakage charge of the piezoelectric material.
2. The piezoelectric sensor according to claim 1, characterized in that, The conversion module includes: a first operational amplifier, the negative input terminal of the first operational amplifier being connected to the output terminal of the piezoelectric material, and a first capacitor being connected between the negative input terminal of the first operational amplifier and the output terminal of the first operational amplifier.
3. The piezoelectric sensor according to claim 1, characterized in that, The first signal amplification module includes: a second operational amplifier, wherein a sliding rheostat is connected to the positive input terminal of the second operational amplifier, and the sliding rheostat is used to adjust the standard industrial signal output by the second operational amplifier.
4. The piezoelectric sensor according to claim 3, characterized in that, The piezoelectric sensor also includes a second signal amplification module for further amplifying the first voltage signal; The second signal amplification module includes a third operational amplifier, the negative input terminal of which is connected to the output terminal of the conversion module, and the output terminal of which is connected to the negative input terminal of the second operational amplifier.
5. The piezoelectric sensor according to claim 4, characterized in that, A second capacitor is connected between the negative input terminal and the output terminal of the third operational amplifier.
6. The piezoelectric sensor according to claim 3, characterized in that, A third capacitor is connected between the negative input terminal and the output terminal of the second operational amplifier.
7. The piezoelectric sensor according to claim 3, characterized in that, The charge compensation module includes: a fourth operational amplifier, the positive input terminal of which is connected to the output terminal of the conversion module via a fourth capacitor; and the negative input terminal of the fourth operational amplifier is connected to the negative input terminal of the second operational amplifier.
8. The piezoelectric sensor according to claim 7, characterized in that, The piezoelectric sensor also includes a charge discharge module, which includes an optocoupler that is turned on when a first signal is received, so that the residual charge is released to ground. The emitter of the optocoupler is grounded, and the collector of the optocoupler is connected to the output terminal of the fourth operational amplifier.
9. The piezoelectric sensor according to claim 8, characterized in that, The charge discharge module includes a fifth operational amplifier; The positive input terminal of the fifth operational amplifier is grounded, and the negative input terminal of the fifth operational amplifier is connected to the collector of the optocoupler, the output terminal of the fourth operational amplifier, and the output terminal of the fifth operational amplifier, respectively.
10. The piezoelectric sensor according to claim 9, characterized in that, The charge discharge module also includes a sixth operational amplifier, the negative input terminal of which is connected to one end of a fifth capacitor, and the other end of the fifth capacitor is connected to the output terminal of the fifth operational amplifier.