CN115560809A - Automatic industrial metering system - Google Patents
Automatic industrial metering system Download PDFInfo
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- CN115560809A CN115560809A CN202211467069.6A CN202211467069A CN115560809A CN 115560809 A CN115560809 A CN 115560809A CN 202211467069 A CN202211467069 A CN 202211467069A CN 115560809 A CN115560809 A CN 115560809A
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- 238000004891 communication Methods 0.000 claims abstract description 10
- 239000003990 capacitor Substances 0.000 claims description 103
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/05—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects
- G01F1/20—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by detection of dynamic effects of the flow
- G01F1/32—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by detection of dynamic effects of the flow using swirl flowmeters
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Abstract
The invention relates to the technical field of industrial metering, and provides an automatic industrial metering system which comprises a main control unit, a communication circuit, a vortex street flow sensor, a charge amplification circuit and a shaping circuit, wherein the input end of the charge amplification circuit is connected with the vortex street flow sensor, the output end of the charge amplification circuit is connected with the input end of the shaping circuit, the output end of the shaping circuit is connected with the main control unit, and the communication circuit is connected with the main control unit. Through above-mentioned technical scheme, the problem that the flowmeter structure is complicated and the precision is low among the prior art has been solved.
Description
Technical Field
The invention relates to the technical field of industrial metering, in particular to an automatic industrial metering system.
Background
Industrial metering refers to the metering work in the field of industrial production, and aims to obtain accurate and reliable measurement data so as to meet various activities required by production and operation of enterprises. The flow is one of four measurands in industrial process control, the flow measurement occupies an indispensable position in the industrial measurement, and the accurate measurement and adjustment of the fluid flow are the basis for ensuring the safe and economic operation of the production process, improving the product quality, reducing the material consumption, improving the economic benefit and realizing scientific management.
The flow meters commonly used at present are classified into: volumetric flow meters, mass flow meters, velocity flow meters, and the like. The volumetric flowmeter has high metering precision, but has complex structure, large volume and heavy weight, and is particularly suitable for medium and small calibers because the volumetric flowmeter with larger calibers has large volume; the mass flowmeter has wide fluid metering range and large pressure loss, and cannot be used for measuring large pipe diameter; the velocity-type flowmeter directly measures the velocity of fluid in a pipeline as a basis for flow measurement, and the measurement result is easily influenced by temperature and the pressure of the measured fluid.
Disclosure of Invention
The invention provides an automatic industrial metering system, which solves the problems of complex structure and low precision of a flowmeter in the prior art.
The technical scheme of the invention is as follows:
an automatic industrial metering system comprises a main control unit, a communication circuit, a vortex street flow sensor, a charge amplification circuit and a shaping circuit, wherein the input end of the charge amplification circuit is connected with the vortex street flow sensor, the output end of the charge amplification circuit is connected with the input end of the shaping circuit, the output end of the shaping circuit is connected with the main control unit, the communication circuit is connected with the main control unit,
the charge amplifying circuit comprises a resistor R1, a capacitor C4, a capacitor C5, an operational amplifier U1, a resistor R2, a capacitor C2, a field effect transistor Q1, a capacitor C3, a resistor R3, a diode D4, a resistor R22 and a field effect transistor Q2,
the inverting input end of the operational amplifier U1 is connected with the first end of a vortex street flow sensor probe U8 through the capacitor C4, the non-inverting input end of the operational amplifier U1 is connected with a Vref power supply, the second end of the vortex street flow sensor probe U8 is connected with the non-inverting input end of the operational amplifier U1 through the capacitor C5, the first end of the resistor R1 is connected with the inverting input end of the operational amplifier U1, the second end of the resistor R1 is connected with the non-inverting input end of the operational amplifier U1, the output end of the operational amplifier U1 is connected with the inverting input end of the operational amplifier U1 through the resistor R2, the output end of the operational amplifier U1 is connected with the inverting input end of the operational amplifier U1 through the capacitor C2, and the output end of the operational amplifier U1 is connected with the input end of the shaping circuit,
the first end of electric capacity C3 is used for connecting drive signal, drive signal is square wave signal, and the same with vortex street flow sensor probe U8's output signal phase place, electric capacity C3's second end passes through resistance R3 connects field effect transistor Q1's grid, electric capacity C3's second end passes through resistance R22 connects field effect transistor Q2's grid, field effect transistor Q1's drain electrode is connected U1's output is put to fortune, field effect transistor Q1's source electrode is connected U1's inverting input end is put to fortune, field effect transistor Q2's drain electrode is connected U1's output is put to fortune, field effect transistor Q2's source electrode is connected U1's inverting input end is put to fortune, diode D3's negative pole is connected field effect transistor Q1's grid, diode D3's positive pole connects the Vref power, diode D4's negative pole Vref connects the power, diode D4's positive pole is connected field effect transistor Q2's grid.
Further, the charge amplifying circuit in the invention further comprises a resistor R23, a resistor R24 and an operational amplifier U9, wherein the non-inverting input terminal of the operational amplifier U9 is connected to the first end of the vortex street flow sensor probe U8 through the resistor R24, the inverting input terminal of the operational amplifier U9 is connected to the second end of the vortex street flow sensor probe U8 through the resistor R23, and the output terminal of the operational amplifier U9 is used as the driving signal and is connected to the first end of the capacitor C3.
Further, the shaping circuit comprises a rheostat RP2, a capacitor C17, a resistor R14, a resistor R15 and an operational amplifier U6, wherein the first end of the capacitor C17 is connected with the output end of the operational amplifier U1, the second end of the capacitor C17 is connected with the non-inverting input end of the operational amplifier U6, the non-inverting input end of the operational amplifier U6 is connected with a 2.5V power supply through the resistor R15, the inverting input end of the operational amplifier U6 is connected with the first end of the rheostat RP2, the second end of the rheostat RP2 is connected with the 2.5V power supply, the output end of the operational amplifier U6 is connected with the inverting input end of the operational amplifier U6 through the resistor R14, and the output end of the operational amplifier U6 is connected with the main control unit.
Further, the invention also comprises a second amplifying circuit, wherein the second amplifying circuit comprises a capacitor C11, a resistor R5, a rheostat RP1, a resistor R4, an operational amplifier U3 and a resistor R6, the first end of the capacitor C11 is connected with the output end of the operational amplifier U1, the second end of the capacitor C11 is connected with the non-inverting input end of the operational amplifier U3, the non-inverting input end of the operational amplifier U3 is connected with a 2.5V power supply through the resistor R5, the inverting input end of the operational amplifier U3 is connected with the first end of the rheostat RP1 through the resistor R4, the second end of the rheostat RP1 is connected with a 5V power supply, the output end of the operational amplifier U3 is connected with the inverting input end of the operational amplifier U3 through the resistor R6, and the output end of the operational amplifier U3 is connected with the first end of the capacitor C17.
Further, the invention also comprises a filter circuit, the filter circuit comprises a resistor R7, a resistor R8, a resistor R9, a capacitor C12, a capacitor C13, a resistor R10, an operational amplifier U4, a capacitor C14, a resistor R11, a capacitor C16, a resistor R12, a resistor R13, a capacitor C15 and an operational amplifier U5, the first end of the resistor R7 is connected with the output end of the operational amplifier U3, the second end of the resistor R7 is connected with the inverting input end of the operational amplifier U4 through the resistor R9, the second end of the resistor R7 is grounded through the capacitor C12, the non-inverting input end of the operational amplifier U4 is grounded through the resistor R10, the output end of the operational amplifier U4 is connected with the inverting input end of the operational amplifier U4 through the capacitor C13, the output end of the operational amplifier U4 is connected with the second end of the resistor R7 through the resistor R8, the output end of the operational amplifier U4 is connected with the first end of the capacitor C14,
the second end of electric capacity C14 passes through electric capacity C16 connects U5's inverting input is put to fortune, electric capacity C14's second end passes through resistance R11 ground connection, U5's non inverting input is put to fortune passes through resistance R12 ground connection, U5's output is put to fortune passes through resistance R13 connects U5's inverting input is put to fortune, U5's output is put to fortune passes through electric capacity C15 connects electric capacity C14's second end, U5's output is put to fortune is connected electric capacity C17's first end.
Further, the current limiter further comprises a current limiting circuit, wherein the current limiting circuit comprises a resistor R16, a resistor R17, a resistor R18, an operational amplifier U7, a diode D1 and a diode D2, the inverting input end of the operational amplifier U7 is connected with the output end of the operational amplifier U6 through the resistor R16, the non-inverting input end of the operational amplifier U7 is grounded through the resistor R18, the output end of the operational amplifier U7 is connected with the inverting input end of the operational amplifier U7 through the resistor R17, the output end of the operational amplifier U7 is connected with the anode of the diode D1, the cathode of the diode D1 is connected with the inverting input end of the operational amplifier U7, the output end of the operational amplifier U7 is connected with the cathode of the diode D2, the anode of the diode D2 is connected with the inverting input end of the operational amplifier U7, and the output end of the operational amplifier U7 is connected with the main control unit.
The working principle and the beneficial effects of the invention are as follows:
the invention detects the flow of the fluid to be detected by a vortex street flow sensor, and the vortex street flow sensor is based on the Karman vortex street effect and consists of a vortex generating body and a detection probe which are designed in a flow field. When liquid flows through the vortex generating body, two rows of vortices which are alternately changed are formed on two sides of the vortex generating body, the vortices are called karman vortex streets, and the alternately changed vortices form a series of alternately changed negative pressure which acts on the vortex street flow sensor probe U8 to form electric charges. The larger the flow rate of the fluid to be measured is, the larger the amount of charge formed on the vortex street flow sensor probe U8 is, that is, the amount of charge is proportional to the flow rate of the fluid to be measured. The electric charge amplifying circuit is used for converting electric charges formed by the vortex street flow sensor probe U8 into voltages, amplifying the voltages and outputting the voltages, the shaping circuit is used for shaping electric signals output by the electric charge amplifying circuit and then sending the electric signals to the main control unit, and the main control unit sends the flow detection data to an upper computer through the communication unit so as to detect the flow data on line in real time.
Specifically, the charge amplifying circuit is used for amplifying a charge signal formed by the probe U8 of the vortex street flow sensor; a voltage signal proportional to the charge is output, and the high input impedance of the vortex street flow sensor is changed into low input impedance. The working principle is as follows:
the operational amplifier U1 forms a differential amplification circuit which can improve the common mode rejection capability of an input stage, and the output end of the vortex street flow sensor probe U8 is connected with the resistor R1 in parallel, so that the problem that limited charges which are to be transmitted to the feedback capacitor C2 are shunted by the input resistor of the operational amplifier U1 to cause charge leakage and zero drift is avoided. The output of the vortex street flow sensor probe U8 is an alternating current signal, the capacitor C4 and the capacitor C5 are used for filtering out a direct current component in the vortex street flow sensor probe U8, and the output of the vortex street flow sensor probe U8 is respectively sent to the non-inverting input end and the inverting input end of the operational amplifier U1. The operational amplifier U1 converts the charge signal formed by the vortex street flow sensor probe U8 into a voltage signal, amplifies the voltage signal and then sends the voltage signal to the shaping circuit.
In order to prevent the output signal distortion of the charge amplification circuit caused by integral saturation from influencing the accuracy of final flow detection, a discharge reset circuit is connected in parallel with a feedback loop of the operational amplifier U1, and forcibly discharges and resets a capacitor C2 when the output signal of the vortex street flow sensor probe U8 crosses zero, wherein the discharge reset circuit is composed of a field effect tube Q1, a capacitor C3, a resistor R3, a diode D4, a resistor R22 and a field effect tube Q2. Wherein Va is a driving signal which is a rectangular wave having the same phase and frequency as the output signal of the vortex street flow sensor probe U8. When the output signal of the vortex street flow sensor probe U8 changes from negative to positive and passes through zero, va changes from low level to high level and is coupled to the grids of the field effect tube Q1 and the field effect tube Q2 through a capacitor C3; at this time, the gate-source voltage of the field effect transistor Q1 is positive and higher than the turn-on voltage, the field effect transistor Q1 is turned on, the feedback capacitor C2 is short-circuited, and the redundant charges are discharged, so that the operational amplifier U1 outputs forced zero-crossing. Then the output signal of the probe U8 of the vortex street flow sensor enters a positive half cycle, the output signal of the operational amplifier U1 correspondingly enters a negative half cycle, the drain-source voltage of the field effect transistor Q1 is negative, the field effect transistor Q1 is disconnected, and the circuit is recovered to be in a normal state. Similarly, when the output signal of the probe U8 of the vortex street flow sensor passes through zero from positive to negative, va changes from high level to low level, the grid-source voltage of the field-effect tube Q2 is negative and is lower than the starting voltage, the field-effect tube Q2 is conducted, the feedback capacitor C2 is short-circuited, and redundant charges are discharged; then, the output signal of the operational amplifier U1 enters a positive half cycle, the drain-source voltage of the field effect transistor Q2 is positive, and the field effect transistor Q2 is disconnected. The operation is repeated in such a way, so that the normal operation of the charge amplifying circuit is ensured.
In the invention, the discharge reset circuit is added on the basis of the original charge amplifying circuit, so that the distortion of the output signal of the charge amplifying circuit is reduced, and the regulation of a post-stage signal is more facilitated, thereby improving the flow detection precision.
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Drawings
FIG. 1 is a circuit diagram of a charge amplification circuit of the present invention;
FIG. 2 is a circuit diagram of a zero crossing detection circuit of the present invention;
FIG. 3 is a circuit diagram of a shaping circuit of the present invention;
FIG. 4 is a circuit diagram of a second amplifier circuit of the present invention;
FIG. 5 is a circuit diagram of a filter circuit according to the present invention;
fig. 6 is a circuit diagram of a limiter circuit according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall relate to the scope of protection of the present invention.
Example 1
As shown in fig. 1, the embodiment provides an automatic industrial metering system, which includes a main control unit, a communication circuit, a vortex street flow sensor, a charge amplification circuit and a shaping circuit, wherein an input end of the charge amplification circuit is connected to the vortex street flow sensor, an output end of the charge amplification circuit is connected to an input end of the shaping circuit, an output end of the shaping circuit is connected to the main control unit, the communication circuit is connected to the main control unit, the charge amplification circuit includes a resistor R1, a capacitor C4, a capacitor C5, an operational amplifier U1, a resistor R2, a capacitor C2, a field effect transistor Q1, a capacitor C3, a resistor R3, a diode D4, a resistor R22 and a field effect transistor Q2, an inverting input end of the operational amplifier U1 is connected to a first end of a probe U8 of the vortex street flow sensor through the capacitor C4, a non-inverting input end of the operational amplifier U1 is connected to a Vref power supply, a second end of the probe U8 of the vortex street flow sensor is connected to a non-inverting input end of the operational amplifier U1 through the capacitor C5, the first end of the resistor R1 is connected with the inverting input end of the operational amplifier U1, the second end of the resistor R1 is connected with the non-inverting input end of the operational amplifier U1, the output end of the operational amplifier U1 is connected with the inverting input end of the operational amplifier U1 through the resistor R2, the output end of the operational amplifier U1 is connected with the inverting input end of the operational amplifier U1 through the capacitor C2, the output end of the operational amplifier U1 is connected with the input end of the shaping circuit, the first end of the capacitor C3 is used for connecting a driving signal, the driving signal is a square wave signal and has the same phase as the output signal of the vortex street flow sensor probe U8, the second end of the capacitor C3 is connected with the grid electrode of the field-effect tube Q1 through the resistor R3, the second end of the capacitor C3 is connected with the grid electrode of the field-effect tube Q2 through the resistor R22, the drain electrode of the field-effect tube Q1 is connected with the output end of the operational amplifier U1, the source electrode of the field-effect tube Q1 is connected with the inverting input end of the operational amplifier U1, the source electrode of the field-effect tube Q2 is connected with the inverting input end of the operational amplifier U1, the cathode of the diode D3 is connected with the grid electrode of the field-effect tube Q1, the anode of the diode D3 is connected with the Vref power supply, the cathode of the diode D4 is connected with the Vref power supply, and the anode of the diode D4 is connected with the grid electrode of the field-effect tube Q2.
The vortex street flow sensor is arranged on a measured fluid pipeline of the industrial production system and is used for detecting the flow of fluid, and the measured fluid can be liquid or gas.
The vortex street flow sensor is based on the Karman vortex street effect and consists of a vortex generating body and a detection probe which are designed in a flow field. When liquid flows through the vortex generating body, two rows of vortices which are alternately changed are formed on two sides of the vortex generating body, the vortices are called karman vortex streets, and the alternately changed vortices form a series of alternately changed negative pressure which acts on the vortex street flow sensor probe U8 to form electric charges. The larger the flow rate of the fluid to be measured is, the larger the amount of charge formed on the vortex street flow sensor probe U8 is, that is, the amount of charge is proportional to the flow rate of the fluid to be measured. The electric charge amplifying circuit is used for converting electric charges formed by the vortex street flow sensor probe U8 into voltages, amplifying the voltages and outputting the voltages, the shaping circuit is used for shaping electric signals output by the electric charge amplifying circuit and then sending the electric signals to the main control unit, and the main control unit sends the flow detection data to an upper computer through the communication unit so as to detect the flow data on line in real time.
Specifically, the charge amplifying circuit is used for amplifying a charge signal formed by the probe U8 of the vortex street flow sensor; an electrical signal proportional to the charge is output, while the high input impedance of the vortex shedding flow sensor is changed to a low input impedance. The working principle is as follows:
the operational amplifier U1 forms a differential amplification circuit, the differential amplification circuit can improve the common mode rejection capability of the input stage, and the operational amplifier U1 adopts a single power supply form, so that a direct current Vref power supply is superposed on the non-inverting input end of the operational amplifier U1, the output of the vortex street flow sensor probe U1 is converted into positive voltage, and then the positive voltage is input into the operational amplifier U1. The output end of the vortex street flow sensor probe U8 is connected with the resistor R1 in parallel, so that the zero drift caused by charge leakage due to the fact that limited charges which should be transmitted to the feedback capacitor C2 are shunted by the input resistor of the operational amplifier U1 is avoided. The output of the vortex street flow sensor probe U8 is an alternating current signal, the capacitor C4 and the capacitor C5 are used for filtering a direct current component in the vortex street flow sensor probe U8, and the output of the vortex street flow sensor probe U8 is respectively sent to the non-inverting input end and the inverting input end of the operational amplifier U1. The operational amplifier U1 converts the charge signal formed by the vortex street flow sensor probe U8 into a voltage signal, amplifies the voltage signal and then sends the voltage signal to the shaping circuit.
In order to prevent the distortion of an output signal caused by integral saturation of a charge amplifying circuit from influencing the accuracy of final flow detection, a discharge reset circuit is connected in parallel to a feedback loop of an operational amplifier U1, and is forced to discharge and reset a capacitor C2 when the output signal of a vortex street flow sensor probe U8 crosses zero, wherein the discharge reset circuit is composed of a field effect tube Q1, a capacitor C3, a resistor R3, a diode D4, a resistor R22 and a field effect tube Q2. Wherein Va is a driving signal which is a rectangular wave having the same phase and frequency as the output signal of the vortex street flow sensor probe U8.
When the output signal of the vortex street flow sensor probe U8 changes from negative to positive and passes through zero, va changes from low level to high level and is coupled to the grids of the field effect tube Q1 and the field effect tube Q2 through a capacitor C3; at this time, the gate-source voltage of the field effect transistor Q1 is positive and higher than the turn-on voltage, the field effect transistor Q1 is turned on, the feedback capacitor C2 is short-circuited, and the redundant charges are discharged, so that the operational amplifier U1 outputs forced zero-crossing. After that, the output signal of the probe U8 of the vortex street flow sensor enters a positive half cycle, the output signal of the operational amplifier U1 correspondingly enters a negative half cycle, the drain-source voltage of the field effect tube Q1 is negative, the field effect tube Q1 is disconnected, and the circuit is recovered to be in a normal state.
Similarly, when the output signal of the probe U8 of the vortex street flow sensor passes through zero from positive to negative, va changes from high level to low level, the grid-source voltage of the field-effect tube Q2 is negative and is lower than the starting voltage, the field-effect tube Q2 is conducted, the feedback capacitor C2 is short-circuited, and redundant charges are discharged; then, the output signal of the operational amplifier U1 enters a positive half cycle, the drain-source voltage of the field effect transistor Q2 is positive, and the field effect transistor Q2 is disconnected. The operation is repeated in this way, so that the normal operation of the charge amplifying circuit is ensured.
Because the flowmeter is mostly arranged outdoors, when the flowmeter is communicated with an upper computer, a longer signal line is easy to introduce thunder, two lightning protection diodes Z1 and Z2 are connected in parallel at the output end of the vortex street flow sensor probe U8 in an opposite phase manner, and the input end of the circuit is protected by static electricity and lightning.
In the embodiment, the discharge reset circuit is added on the basis of the original charge amplification circuit, so that the distortion of the output signal of the charge amplification circuit is reduced, the conditioning of a post-stage signal is facilitated, and the detection precision of the flow is improved.
As shown in fig. 2, the charge amplifying circuit in this embodiment further includes a resistor R23, a resistor R24, and an operational amplifier U9, wherein a non-inverting input terminal of the operational amplifier U9 is connected to a first end of the vortex street flow sensor probe U8 through the resistor R24, an inverting input terminal of the operational amplifier U9 is connected to a second end of the vortex street flow sensor probe U8 through the resistor R23, and an output terminal of the operational amplifier U9 is used as a driving signal and is connected to a first end of the capacitor C3.
In order to ensure that a Va signal and a signal output by a vortex flow sensor probe U8 have the same phase and the same frequency, a zero-crossing detection circuit is added, and the zero-crossing detection circuit is composed of a resistor R23, a resistor R24, an operational amplifier U9 and a resistor R25.
In the positive half cycle of the output signal of the vortex street flow sensor probe U8, the voltage of the in-phase input end of the operational amplifier U9 is higher than the voltage of the reverse-phase input end of the operational amplifier U9, and the operational amplifier U9 outputs a high level to the first end of the capacitor C3; when the output signal of the vortex street flow sensor probe U8 is changed from positive to negative, the voltage of the reverse phase input end of the operational amplifier U9 is higher than the voltage of the non-phase input end of the operational amplifier U9, and the operational amplifier U9 outputs a low level signal to the first end of the capacitor C3. The resistor R25 and the capacitor C8 form a filter circuit for filtering high-frequency clutter signals in rectangular waves output by the operational amplifier U9.
As shown in fig. 3, the shaping circuit in this embodiment includes a rheostat RP2, a capacitor C17, a resistor R14, a resistor R15, and an operational amplifier U6, a first end of the capacitor C17 is connected to an output end of the operational amplifier U1, a second end of the capacitor C17 is connected to a non-inverting input end of the operational amplifier U6, the non-inverting input end of the operational amplifier U6 is connected to a 2.5V power supply through the resistor R15, an inverting input end of the operational amplifier U6 is connected to a first end of the rheostat RP2, a second end of the rheostat RP2 is connected to a 2.5V power supply, an output end of the operational amplifier U6 is connected to an inverting input end of the operational amplifier U6 through the resistor R14, and an output end of the operational amplifier U6 is connected to the main control unit.
The resistor RP2, the capacitor C17, the resistor R14, the resistor R15 and the operational amplifier U6 form a Schmidt trigger, and the edge of the output voltage waveform is steep through a positive feedback process in the circuit. By utilizing the characteristic, the signal waveform with slow edge change can be shaped into the rectangular pulse with steep edge, the noise superimposed on the high and low levels of the rectangular pulse signal can be effectively eliminated, and the main control unit judges the flow of the fluid to be detected by receiving the number of pulses output by the shaping circuit in unit time.
As shown in fig. 4, the current-limiting circuit further includes a capacitor C11, a resistor R5, a varistor RP1, a resistor R4, an operational amplifier U3, and a resistor R6, wherein a first end of the capacitor C11 is connected to an output end of the operational amplifier U1, a second end of the capacitor C11 is connected to a non-inverting input end of the operational amplifier U3, the non-inverting input end of the operational amplifier U3 is connected to a 2.5V power supply through the resistor R5, a non-inverting input end of the operational amplifier U3 is connected to a first end of the varistor RP1 through the resistor R4, a second end of the varistor RP1 is connected to the 5V power supply, an output end of the operational amplifier U3 is connected to a non-inverting input end of the operational amplifier U3 through the resistor R6, and an output end of the operational amplifier U3 is connected to a first end of the capacitor C17.
Although the charge amplifying circuit amplifies the charges generated by the vortex street flow sensor probe U8, the output voltage of the operational amplifier U1 is only about tens of millivolts and is still weak, so that further voltage amplification is required.
A second amplifying circuit is added between the charge amplifying circuit and the shaping circuit, wherein a capacitor C11, a resistor R5, a rheostat RP1, a resistor R4, an operational amplifier U3 and a resistor R6 form the second amplifying circuit, an alternating signal is output by the operational amplifier U1, and the operational amplifier U3 forms an alternating current amplifier with deep negative feedback. The resistor R5 is used as a balance resistor, because the input resistance of the in-phase amplifier is higher, when the in-phase end balance resistor R5 is not connected, the input resistance of the operational amplifier U3 is between 10M omega and 100M omega, after the in-phase end balance resistor R5 is connected, the input resistance is mainly determined by the value of the resistor R5, the second amplifying circuit amplifies an alternating current signal, and the second amplifying circuit utilizes the coupling capacitor C11 and the in-phase end input resistor of the operational amplifier U3 to form a high-pass filter to play the roles of blocking direct coupling and low-frequency filtering. The output voltage amplitude of the operational amplifier U3 can be changed by adjusting the resistance value of the rheostat RP1, and ideal amplified output can be obtained by adjusting the rheostat RP1 when the flow meter detects the flow of different media. Thereby improving the range of the flowmeter.
As shown in fig. 5, the present embodiment further includes a filter circuit, the filter circuit includes a resistor R7, a resistor R8, a resistor R9, a capacitor C12, a capacitor C13, a resistor R10, an operational amplifier U4, a capacitor C14, a resistor R11, a capacitor C16, a resistor R12, a resistor R13, a capacitor C15 and an operational amplifier U5, the first end of the resistor R7 is connected to the output end of the operational amplifier U3, the second end of the resistor R7 is connected to the inverting input end of the operational amplifier U4 through the resistor R9, the second end of the resistor R7 is grounded through the capacitor C12, the non-inverting input end of the operational amplifier U4 is grounded through the resistor R10, the output end of the operational amplifier U4 is connected to the inverting input end of the operational amplifier U4 through the capacitor C13, the output end of the operational amplifier U4 is connected to the second end of the resistor R8, the output end of the operational amplifier U4 is connected to the first end of the capacitor C14, the second end of the capacitor C14 is connected to the inverting input end of the operational amplifier U5 through the capacitor C13, the second end of the operational amplifier U5 is grounded through the non-inverting input end of the resistor R12, and the inverting input end of the capacitor C14 is connected to the output end of the operational amplifier U5, the capacitor C17.
The vortex street signal changes with the flow change of the measured fluid, the value is between 1 to 2000Hz under different pipe diameters and mediums, the frequency of the interference signal also changes with the change of the frequency of the vortex street signal, when the flow of the measured fluid is smaller, the flow velocity of the fluid is smaller, and when the flow velocity is smaller, the signal is weaker, the interference is more obvious. The interference signal may completely cover the detected signal, and if the interference signal is not processed, the accuracy of the flow detection will be affected. Therefore, a filter circuit is added between the second amplifying circuit and the shaping circuit for filtering the interference signals.
The resistor R7, the resistor R8, the resistor R9, the capacitor C12, the capacitor C13, the resistor R10 and the operational amplifier U4 form a second-order low-pass filter circuit for filtering high-frequency clutter in the flow detection process; the capacitor C14, the resistor R11, the capacitor C16, the resistor R12, the resistor R13, the capacitor C15 and the operational amplifier U5 form a second-order high-pass filter circuit, noise interference can be introduced into the resistors in the conversion and transmission processes of electric signals, and the second-order high-pass filter circuit is used for filtering noise interference signals in the circuit.
As shown in fig. 6, the current limiter further includes a current limiting circuit, the current limiting circuit includes a resistor R16, a resistor R17, a resistor R18, an operational amplifier U7, a diode D1 and a diode D2, an inverting input terminal of the operational amplifier U7 is connected to an output terminal of the operational amplifier U6 through the resistor R16, a non-inverting input terminal of the operational amplifier U7 is grounded through the resistor R18, an output terminal of the operational amplifier U7 is connected to an inverting input terminal of the operational amplifier U7 through the resistor R17, an output terminal of the operational amplifier U7 is connected to an anode of the diode D1, a cathode of the diode D1 is connected to an inverting input terminal of the operational amplifier U7, an output terminal of the operational amplifier U7 is connected to a cathode of the diode D2, an anode of the diode D2 is connected to an inverting input terminal of the operational amplifier U7, and an output terminal of the operational amplifier U7 is connected to the main control unit.
Because the main control unit has limited ability to bear the electric signal, when the amplitude of the electric signal input into the main control unit exceeds the limit which can be borne by the main control unit, permanent damage can be caused to the main control unit, and therefore, an amplitude limiting circuit is added between the filter circuit and the main control unit.
The amplitude limiting circuit is used for clamping the signal level output by the operational amplifier U5, so that interference is further eliminated, and the signal-to-noise ratio of the circuit is improved. And a feedback resistor R17 of the operational amplifier U7 is connected with a voltage stabilizing tube D1 and a voltage stabilizing tube D2 in parallel in an inverted way, so that an amplitude limiting circuit is formed, and when the output of the operational amplifier U7 reaches the stable voltage of the voltage stabilizing tube, the voltage stabilizing tube can make the feedback resistor R17 lose the effect, so that the output of the operational amplifier U7 is limited. In order to obtain bipolar clipping, two voltage regulators are used in this embodiment.
The present invention is not limited to the above preferred embodiments, and any modifications, equivalent substitutions, improvements, etc. within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. An automatic industrial metering system is characterized by comprising a main control unit, a communication circuit, a vortex street flow sensor, a charge amplification circuit and a shaping circuit, wherein the input end of the charge amplification circuit is connected with the vortex street flow sensor, the output end of the charge amplification circuit is connected with the input end of the shaping circuit, the output end of the shaping circuit is connected with the main control unit, the communication circuit is connected with the main control unit,
the charge amplifying circuit comprises a resistor R1, a capacitor C4, a capacitor C5, an operational amplifier U1, a resistor R2, a capacitor C2, a field effect transistor Q1, a capacitor C3, a resistor R3, a diode D4, a resistor R22 and a field effect transistor Q2,
the inverting input end of the operational amplifier U1 is connected with the first end of a vortex street flow sensor probe U8 through the capacitor C4, the non-inverting input end of the operational amplifier U1 is connected with a Vref power supply, the second end of the vortex street flow sensor probe U8 is connected with the non-inverting input end of the operational amplifier U1 through the capacitor C5, the first end of the resistor R1 is connected with the inverting input end of the operational amplifier U1, the second end of the resistor R1 is connected with the non-inverting input end of the operational amplifier U1, the output end of the operational amplifier U1 is connected with the inverting input end of the operational amplifier U1 through the resistor R2, the output end of the operational amplifier U1 is connected with the inverting input end of the operational amplifier U1 through the capacitor C2, and the output end of the operational amplifier U1 is connected with the input end of the shaping circuit,
the first end of electric capacity C3 is used for connecting drive signal, drive signal is square wave signal, and the same with vortex street flow sensor probe U8's output signal phase place, electric capacity C3's second end passes through resistance R3 connects field effect transistor Q1's grid, electric capacity C3's second end passes through resistance R22 connects field effect transistor Q2's grid, field effect transistor Q1's drain electrode is connected U1's output is put to fortune, field effect transistor Q1's source electrode is connected U1's inverting input end is put to fortune, field effect transistor Q2's drain electrode is connected U1's output is put to fortune, field effect transistor Q2's source electrode is connected U1's inverting input end is put to fortune, diode D3's negative pole is connected field effect transistor Q1's grid, diode D3's positive pole connects the Vref power, diode D4's negative pole Vref connects the power, diode D4's positive pole is connected field effect transistor Q2's grid.
2. The automatic industrial metering system of claim 1, wherein the charge amplifying circuit further comprises a resistor R23, a resistor R24 and an operational amplifier U9, a non-inverting input terminal of the operational amplifier U9 is connected to the first end of the vortex street flow sensor probe U8 through the resistor R24, an inverting input terminal of the operational amplifier U9 is connected to the second end of the vortex street flow sensor probe U8 through the resistor R23, and an output terminal of the operational amplifier U9 is used as the driving signal and connected to the first end of the capacitor C3.
3. The automatic industrial metering system of claim 1, wherein the shaping circuit comprises a rheostat RP2, a capacitor C17, a resistor R14, a resistor R15 and an operational amplifier U6, a first end of the capacitor C17 is connected to an output end of the operational amplifier U1, a second end of the capacitor C17 is connected to a non-inverting input end of the operational amplifier U6, a non-inverting input end of the operational amplifier U6 is connected to a 2.5V power supply through the resistor R15, an inverting input end of the operational amplifier U6 is connected to a first end of the rheostat RP2, a second end of the rheostat RP2 is connected to a 2.5V power supply, an output end of the operational amplifier U6 is connected to an inverting input end of the operational amplifier U6 through the resistor R14, and an output end of the operational amplifier U6 is connected to the main control unit.
4. The automatic industrial metering system of claim 3, further comprising a second amplifying circuit, wherein the second amplifying circuit comprises a capacitor C11, a resistor R5, a rheostat RP1, a resistor R4, an operational amplifier U3 and a resistor R6, a first end of the capacitor C11 is connected to an output end of the operational amplifier U1, a second end of the capacitor C11 is connected to a non-inverting input end of the operational amplifier U3, a non-inverting input end of the operational amplifier U3 is connected to a 2.5V power source through the resistor R5, an inverting input end of the operational amplifier U3 is connected to a first end of the rheostat RP1 through the resistor R4, a second end of the rheostat RP1 is connected to a 5V power source, an output end of the operational amplifier U3 is connected to an inverting input end of the operational amplifier U3 through the resistor R6, and an output end of the operational amplifier U3 is connected to a first end of the capacitor C17.
5. The automatic industrial metering system of claim 4, further comprising a filter circuit, wherein the filter circuit comprises a resistor R7, a resistor R8, a resistor R9, a capacitor C12, a capacitor C13, a resistor R10, an operational amplifier U4, a capacitor C14, a resistor R11, a capacitor C16, a resistor R12, a resistor R13, a capacitor C15 and an operational amplifier U5, a first end of the resistor R7 is connected to an output end of the operational amplifier U3, a second end of the resistor R7 is connected to an inverting input end of the operational amplifier U4 through the resistor R9, a second end of the resistor R7 is connected to ground through the capacitor C12, a non-inverting input end of the operational amplifier U4 is connected to ground through the resistor R10, an output end of the operational amplifier U4 is connected to an inverting input end of the operational amplifier U4 through the capacitor C13, an output end of the operational amplifier U4 is connected to a second end of the resistor R7 through the resistor R8, an output end of the operational amplifier U4 is connected to a first end of the capacitor C14,
the second end of electric capacity C14 passes through electric capacity C16 connects U5's inverting input is put to fortune, electric capacity C14's second end passes through resistance R11 ground connection, U5's non inverting input is put to fortune passes through resistance R12 ground connection, U5's output is put to fortune passes through resistance R13 connects U5's inverting input is put to fortune, U5's output is put to fortune passes through electric capacity C15 connects electric capacity C14's second end, U5's output is put to fortune is connected electric capacity C17's first end.
6. The automatic industrial metering system of claim 3, further comprising a limiting circuit, wherein the limiting circuit comprises a resistor R16, a resistor R17, a resistor R18, an operational amplifier U7, a diode D1 and a diode D2, an inverting input terminal of the operational amplifier U7 is connected to an output terminal of the operational amplifier U6 through the resistor R16, a non-inverting input terminal of the operational amplifier U7 is grounded through the resistor R18, an output terminal of the operational amplifier U7 is connected to an inverting input terminal of the operational amplifier U7 through the resistor R17, an output terminal of the operational amplifier U7 is connected to an anode of the diode D1, a cathode of the diode D1 is connected to the inverting input terminal of the operational amplifier U7, an output terminal of the operational amplifier U7 is connected to a cathode of the diode D2, an anode of the diode D2 is connected to the inverting input terminal of the operational amplifier U7, and an output terminal of the operational amplifier U7 is connected to the main control unit.
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