An automatic zeroing circuit for pneumatic pressure monitoring and method thereof

Abstract

The application discloses an automatic zero clearing circuit and method for pneumatic pressure monitoring, and belongs to the technical field of pressure sensors. The application provides a pure analog circuit solution for the zero drift problem of existing sensors. The circuit comprises a pressure signal acquisition and buffer module, an external trigger interface module, a sample and hold module, and a subtraction operation module. The core is that the external trigger interface module receives a trigger signal from a pneumatic control system (such as a charge / discharge valve controller), and the signal is synchronized with the discharge / charge state of the pneumatic pipeline. The sample and hold module accurately samples and memorizes the sensor zero voltage when the pipeline is discharged under the control of the trigger signal, and keeps the voltage when the pipeline is charged. The subtraction operation module subtracts the memorized zero voltage from the buffered sensor output signal in real time, thereby eliminating the drift. The application does not require digital devices such as single-chip microcomputers, has a simple circuit structure, low cost, strong anti-interference performance, and is especially suitable for industrial pneumatic pressure monitoring scenes.

Description

Technical Field

[0001] This invention belongs to the field of pressure sensor technology, specifically relating to an automatic zeroing circuit and method for pneumatic pressure monitoring, which is particularly suitable for pressure measurement scenarios where zero drift exists and it needs to work in conjunction with an industrial pneumatic control system. Background Technology

[0002] In industrial automation, pressure sensors are widely used to monitor the pressure of media in pneumatic pipelines. Sensors are typically calibrated before leaving the factory, but in actual use, factors such as changes in ambient temperature and component aging can cause the sensor's zero-point voltage to drift. This drift is superimposed on the sensor's output signal, causing subsequent data acquisition systems to fail to accurately reflect the true pressure changes.

[0003] like Figure 1 As shown, the traditional solution involves using an analog-to-digital converter (ADC) and a microcontroller (MCU) to digitize the signal and eliminate drift through software algorithms (such as real-time zero-point subtraction). However, this approach is circuitically complex, costly, and requires programming the microcontroller. More importantly, in highly interference-prone industrial environments, the microcontroller system is susceptible to interference, which can cause the program to malfunction or crash, leading to decreased system reliability.

[0004] To address the aforementioned issues, some purely analog circuit solutions have been proposed. However, their control logic is typically independent of the operating state of the field equipment, making it difficult to achieve accurate zero-point sampling synchronized with the operating conditions. Therefore, an automatic zeroing solution that can work collaboratively with industrial control systems, is simple in structure, and offers high reliability is needed. Summary of the Invention

[0005] The purpose of this invention is to provide an automatic zeroing circuit and method for pneumatic pressure monitoring, so as to solve the problems of complex circuits, high cost, poor anti-interference and difficulty in accurately synchronizing with field conditions in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: An automatic zeroing circuit for pneumatic pressure monitoring includes: The pressure signal acquisition and buffering module is connected to the pressure sensor and is used to acquire the sensor output signal, which includes zero-point drift, in real time and buffer and isolate the signal to provide two identical low-impedance outputs. An external trigger interface module is used to receive trigger signals from the pneumatic control system, the trigger signals being synchronized with the operating status of the pneumatic pipeline; The sample-and-hold module, which is connected to one output of the pressure signal acquisition and buffer module and the external trigger interface module, is used to selectively sample and memorize the zero-point voltage in the sensor output signal under the control of the trigger signal. The subtraction module, which is connected to another output of the pressure signal acquisition and buffer module and the sample-and-hold module, is used to subtract the zero-point voltage stored in the sample-and-hold module from the currently acquired sensor output signal in real time to eliminate the influence of zero-point drift.

[0007] Furthermore, it also includes a low-pass filter module, which is connected to the output of the subtraction module, and is used to filter the voltage signal after the subtraction operation to output a smooth pressure response signal.

[0008] Furthermore, the external trigger interface module includes: an optocoupler, the input of which is used to receive a first-level trigger signal from the pneumatic control system; and a level conversion circuit, connected to the output of the optocoupler, used to convert the first-level trigger signal into a second-level control signal compatible with the logic level of the sample-and-hold module.

[0009] Preferably, the level conversion circuit includes at least one MOS transistor for shaping and level conversion of the signal output from the optocoupler.

[0010] Furthermore, the power supply of the external trigger interface module is isolated from the analog power supply of the sample-and-hold module and the subtraction operation module.

[0011] Furthermore, the pressure signal acquisition and buffering module includes a voltage follower consisting of at least two operational amplifiers, used to buffer and distribute the sensor signal.

[0012] Furthermore, the sample-and-hold module includes: a sample-and-hold chip, whose signal input terminal is connected to one output of the pressure signal acquisition and buffer module, and whose control terminal is connected to the external trigger interface module; and a holding capacitor, connected to the sample-and-hold chip, for storing the zero-point voltage.

[0013] Furthermore, the subtraction module is a differential amplifier circuit or a subtractor circuit based on an operational amplifier.

[0014] Furthermore, the present invention also provides an automatic zeroing method for a pressure sensor based on the above circuit, comprising the following steps: Step 1: When the pneumatic control system puts the pneumatic pipeline in the exhaust state and the pressure sensor senses the zero-point pressure, the external trigger interface module receives the first trigger signal from the controller and controls the sample-and-hold module to enter the sampling and memory state, sample and store the current sensor zero-point voltage; Step 2: When the pneumatic control system puts the pneumatic pipeline into an inflatable state and the pressure sensor senses the medium pressure, the external trigger interface module receives a second trigger signal from the controller and controls the sample-and-hold module to enter the holding state, continuously outputting the previously memorized zero-point voltage. Step 3: The subtraction module receives the real-time sensor voltage output by the pressure signal acquisition and buffer module and the memory zero-point voltage output by the sample-and-hold module, performs the subtraction operation, and outputs a pressure response voltage that eliminates zero-point drift.

[0015] Beneficial effects Compared with the prior art, the beneficial effects of the present invention are: Simple structure and low cost: No expensive digital components such as ADC and MCU are required, and no software development is needed, which significantly reduces hardware costs.

[0016] High reliability and strong anti-interference capability: The absence of a microcontroller avoids software failures such as program crashes and freezes. Through optocoupler isolation and independent power supply design, external interference that may be introduced into the industrial environment (such as 24V control signals) is effectively isolated from the core analog circuitry (such as ±15V power supply), greatly improving the system's anti-interference capability and stability. Simultaneously, the signal buffer module enhances driving capability and improves signal quality.

[0017] Precise synchronization enables dynamic zeroing: By linking with the pneumatic control system, the control signal is used to accurately distinguish between the zero sampling stage and the pressure measurement stage, achieving "dynamic" automatic zeroing synchronized with the operating conditions, ensuring that the latest zero drift value is deducted before each measurement.

[0018] Strong self-recovery capability: As it is a pure hardware circuit, the circuit can immediately return to normal working state after the external interference signal disappears, and there will be no abnormal situations such as "crashing" that require manual intervention.

[0019] Pure output signal: The low-pass filter module effectively filters out high-frequency noise, making the output signal smoother and more stable, which is convenient for subsequent acquisition equipment to use directly. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a block diagram of the pressure acquisition circuit architecture with a microcontroller in the existing technology.

[0022] Figure 2This is an overall architecture block diagram of an embodiment of the present invention.

[0023] Figure 3 This is a schematic diagram of the pressure signal acquisition and buffering module in an embodiment of the present invention.

[0024] Figure 4 This is a schematic diagram of the sample-and-hold module in an embodiment of the present invention.

[0025] Figure 5 This is a schematic diagram of the subtraction operation module in an embodiment of the present invention.

[0026] Figure 6 This is a schematic diagram of the low-pass filter module in an embodiment of the present invention.

[0027] Figure 7 This is a schematic diagram of the external trigger interface module in an embodiment of the present invention.

[0028] Figure 8 This is a schematic diagram of the pneumatic principle and external valve controller used in this invention. Detailed Implementation

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0030] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] Example 1: Circuit Structure like Figures 2 to 7 As shown in the figure, this embodiment provides an automatic zeroing circuit for pneumatic pressure monitoring, including: a pressure signal acquisition and buffering module, an external trigger interface module, a sample and hold module, a subtraction operation module, and a low-pass filter module.

[0032] Pressure signal acquisition and buffering module: such as Figure 3 As shown, the circuit mainly consists of two voltage followers, primarily composed of operational amplifiers IC1A and IC1B. Sensor interface J1 introduces the pressure sensor's output signal into the circuit. One path is buffered by IC1A and sent to the input V2 of the subtraction module; the other path is buffered by IC1B and sent to the input of the sample-and-hold module (pin 1 of the sample-and-hold chip IC4). This module achieves low-impedance buffering and distribution of the sensor signal, providing two identical, high-drive signals for subsequent circuits.

[0033] External trigger interface module: such as Figure 7The key improvement of this invention is shown below. This module includes interface J3, optocoupler U1, MOSFETs Q1 and Q2, and related resistors. Interface J3 connects to the pneumatic system's charging / discharging valve controller. When the pipeline is venting, the controller outputs a DC 24V trigger signal; when the pipeline is charging, the controller outputs 0V.

[0034] Isolation and Conversion: The DC 24V signal, after being current-limited by R12, drives the LED of optocoupler U1. The phototransistor of U1 conducts, and its output signal is then shaped and level-converted by a circuit consisting of Q1 and Q2, ultimately outputting a 3.3V control signal IC4_EN compatible with the logic level of the sample-and-hold chip. The +24V power supply is completely isolated from +5V and ±15V, and the analog ground AGND is isolated from the trigger circuit ground, ensuring that industrial interference does not enter the core analog circuit.

[0035] Sample and hold module: such as Figure 4 As shown, it mainly consists of a sample-and-hold chip IC4 (such as LF398) and a holding capacitor C3. The signal input terminal (pin 1) of the sample-and-hold chip IC4 receives the sensor signal from the pressure signal acquisition and buffer module (IC1B). The control terminal (pin 11) of IC4 receives the IC4_EN signal from the external trigger interface module.

[0036] Operating logic: When IC4_EN is high (3.3V), IC4 is in "sampling" mode, and its output (pin 7) follows the input in real time and charges capacitor C3 to remember the current voltage; when IC4_EN is low (0V), IC4 is in "hold" mode, and its output holds the voltage value stored on capacitor C3 until the next sampling signal arrives.

[0037] Subtraction module: such as Figure 5 As shown, a typical subtractor circuit is constructed from operational amplifier IC2A and external resistors R1, R2, R5, and R6. Its input terminal V2 is connected to the real-time sensor signal (from IC1A of the pressure signal acquisition and buffer module), and its input terminal V3 is connected to the output of the sample-and-hold module (from IC4). According to the subtractor principle, its output voltage V4 satisfies: V4 = V2 - V3.

[0038] Low-pass filter module: such as Figure 6 As shown, a second-order active low-pass filter is constructed from operational amplifier IC2B and external resistors R3 and R4, and capacitors C1 and C2. The output voltage V4 of the subtractor is input through R3, filtered, and then output from pin 1 of IC2B to interface J2. This module is used to filter out high-frequency noise and interference in the circuit, outputting a smooth and stable final pressure response signal.

[0039] Example 2: Automatic Reset Method Combination Figure 8 The pneumatic principle diagram is shown below. The automatic zeroing method of this invention is as follows: Phase 1 (Exhaust / Zero-Point Sampling): When the controller closes the charging valve and opens the exhaust valve, the pipeline is open to the atmosphere, and the pressure sensor detects the zero-point pressure. At this time, the controller outputs a trigger signal of DC 24V, which, after processing by the external trigger interface module, results in IC4_EN=3.3V. The sample-and-hold module IC4 enters sampling mode, sampling and memorizing the current zero-point voltage output by the sensor (including the drift ΔV), denoted as V0+ΔV.

[0040] Phase Two (Inflation / Pressure Measurement): When the controller activates the inflation valve and closes the exhaust valve, the measured medium is introduced into the pipeline, and the pressure sensor detects the pressure P. At this time, the controller outputs a trigger signal of DC 0V, which, after processing, is IC4_EN=0V. The sample-and-hold module IC4 enters hold mode, and its output continuously outputs the zero-point voltage V0+ΔV stored in Phase One. Simultaneously, the real-time sensor signal output by the pressure signal acquisition and buffer module is Vp + V0 + ΔV.

[0041] Phase Three (Operation): The input V2 of the subtraction module is Vp + V0 + ΔV, and the input V3 is V0 + ΔV. According to the subtractor formula, the output voltage V4 = (Vp + V0 + ΔV) - (V0 + ΔV) = Vp. At this point, the circuit has successfully eliminated the zero-point drift ΔV, obtaining a pure voltage signal Vp related to the pressure change.

[0042] Phase 4 (Filtered Output): After the signal Vp is filtered by the low-pass filter module to remove residual noise, it is output to the J2 interface for use by the PLC or other data acquisition devices.

[0043] In summary, this invention cleverly utilizes existing pneumatic control signals in industrial settings and combines them with a complete analog signal processing chain to achieve a pure hardware-based, low-cost, highly reliable, and high signal-to-noise ratio automatic zeroing function.

[0044] Preferably, the operational amplifier IC1A and operational amplifier IC1B are two operational amplifiers in the same chip, model OPA2188.

[0045] Preferably, the operational amplifier IC2A and operational amplifier IC2B are two operational amplifiers in the same chip, model OPA2188.

[0046] Preferably, the sample-and-hold chip IC4 is model LF298.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An automatic zeroing circuit for pneumatic pressure monitoring, comprising: The pressure signal acquisition and buffering module is connected to the pressure sensor and is used to acquire the sensor output signal, which includes zero-point drift, in real time and buffer and isolate the signal to provide two identical low-impedance outputs. An external trigger interface module is used to receive trigger signals from the pneumatic control system, the trigger signals being synchronized with the operating status of the pneumatic pipeline; The sample-and-hold module, which is connected to one output of the pressure signal acquisition and buffer module and the external trigger interface module, is used to selectively sample and memorize the zero-point voltage in the sensor output signal under the control of the trigger signal. The subtraction module, which is connected to another output of the pressure signal acquisition and buffer module and the sample-and-hold module, is used to subtract the zero-point voltage stored in the sample-and-hold module from the currently acquired sensor output signal in real time to eliminate the influence of zero-point drift.

2. The automatic zeroing circuit for pneumatic pressure monitoring as described in claim 1, characterized in that, It also includes a low-pass filter module, which is connected to the output of the subtraction module, and is used to filter the voltage signal after the subtraction operation to output a smooth pressure response signal.

3. The automatic zeroing circuit for pneumatic pressure monitoring as described in claim 1, characterized in that, The external trigger interface module includes: an optocoupler, the input of which is used to receive a first-level trigger signal from the pneumatic control system; and a level conversion circuit, connected to the output of the optocoupler, used to convert the first-level trigger signal into a second-level control signal compatible with the logic level of the sample-and-hold module.

4. The automatic zeroing circuit for pneumatic pressure monitoring as described in claim 3, characterized in that, The level conversion circuit includes at least one MOS transistor for shaping and level conversion of the signal output from the optocoupler.

5. The automatic zeroing circuit for pneumatic pressure monitoring as described in claim 1, characterized in that, The power supply of the external trigger interface module is isolated from the analog power supply of the sample-and-hold module and the subtraction operation module.

6. The automatic zeroing circuit for pneumatic pressure monitoring as described in claim 1, characterized in that, The pressure signal acquisition and buffering module includes a voltage follower consisting of at least two operational amplifiers, used to buffer and distribute sensor signals.

7. The automatic zeroing circuit for pneumatic pressure monitoring as described in claim 1, characterized in that, The sample-and-hold module includes: a sample-and-hold chip, whose signal input terminal is connected to one output of the pressure signal acquisition and buffer module, and whose control terminal is connected to the external trigger interface module; and a holding capacitor, connected to the sample-and-hold chip, for storing the zero-point voltage.

8. The automatic zeroing circuit for pneumatic pressure monitoring as described in claim 1, characterized in that, The subtraction module is a differential amplifier circuit or a subtractor circuit based on an operational amplifier.

9. An automatic zeroing method for a pressure sensor based on an automatic zeroing circuit for pneumatic pressure monitoring as described in any one of claims 1 to 8, comprising the following steps: Step 1: When the pneumatic control system puts the pneumatic pipeline in the exhaust state and the pressure sensor senses the zero-point pressure, the external trigger interface module receives the first trigger signal from the controller and controls the sample-and-hold module to enter the sampling and memory state, sample and store the current sensor zero-point voltage; Step 2: When the pneumatic control system puts the pneumatic pipeline into an inflatable state and the pressure sensor senses the medium pressure, the external trigger interface module receives a second trigger signal from the controller and controls the sample-and-hold module to enter the holding state, continuously outputting the previously memorized zero-point voltage. Step 3: The subtraction module receives the real-time sensor voltage output by the pressure signal acquisition and buffer module and the memory zero-point voltage output by the sample-and-hold module, performs the subtraction operation, and outputs a pressure response voltage that eliminates zero-point drift.

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