CN215639606U - Signal processing system for improving signal-to-noise ratio of electromagnetic flowmeter - Google Patents
Signal processing system for improving signal-to-noise ratio of electromagnetic flowmeter Download PDFInfo
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- CN215639606U CN215639606U CN202122119175.2U CN202122119175U CN215639606U CN 215639606 U CN215639606 U CN 215639606U CN 202122119175 U CN202122119175 U CN 202122119175U CN 215639606 U CN215639606 U CN 215639606U
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Abstract
The utility model belongs to the technical field of electromagnetic flowmeters, and particularly relates to a signal processing system for improving the signal-to-noise ratio of an electromagnetic flowmeter. The method is more favorable for detecting the signal of the electromagnetic flowmeter at low flow speed, and improves the flow range ratio. Comprises an electromagnetic flow sensor; two output electrode signals of the sensor pass through the double-shielded cable and then respectively pass through respective common-mode interference filtering units and then are connected with the input end of an instrumentation amplifier U1, and the instrumentation amplifier U1 is also respectively connected with a first buffer U2 and a second buffer U3; the output of the first buffer U2 buffers signals to the guard ring GRA and the output of the second buffer U3 buffers signals to the guard ring GRB; the buffered signals connected to the guard ring circuits GRA, GRB are also connected to the inner shields SA, SB of the double shielded cable, respectively.
Description
Technical Field
The utility model belongs to the technical field of electromagnetic flowmeters, and particularly relates to a signal processing system for improving the signal-to-noise ratio of an electromagnetic flowmeter.
Background
The circuit board of the existing electromagnetic flowmeter has the phenomena of more interference signals and more noise, and the flow range ratio is easy to reduce when the signals of the low-flow-rate electromagnetic flowmeter are detected.
Disclosure of Invention
Aiming at the defects in the prior art, the utility model provides a signal processing system for improving the signal-to-noise ratio of an electromagnetic flowmeter.
In order to achieve the purpose, the utility model adopts the following technical scheme that the device comprises an electromagnetic flow sensor; two output electrode signals of the sensor pass through the double-shielded cable and then respectively pass through respective common-mode interference filtering units and then are connected with the input end of an instrumentation amplifier U1, and the instrumentation amplifier U1 is also respectively connected with a first buffer U2 and a second buffer U3; the output of the first buffer U2 buffers signals to the guard ring GRA and the output of the second buffer U3 buffers signals to the guard ring GRB; the buffered signals connected to the guard ring circuits GRA, GRB are also connected to the inner shields SA, SB of the double shielded cable, respectively.
Further, the sensor includes excitation coils L1, L2, detection electrodes SIGA, SIGB, a ground electrode SG; wherein, the detection electrode signals SIGA and SIGB are respectively connected to the 1 pin and the 4 pin of the connector P1 through two inner core wires of the double-shielded cable; the grounding electrode SG is connected to an outer shielding layer of the double-shielded cable, then is connected to a pin 5 of a connector P1, passes through a connector P1 and then is connected to a signal ground end GND; the inner shields SA, SB of the double shielded cable are connected to pins 2, 3 of the connector P1, respectively.
Furthermore, the guard ring circuits GRA and GRB are used to surround the circuit from the pins 1 and 4 of the connector P1 to the pins 1 and 4 of the inverting input terminal of the instrumentation amplifier U1, respectively, and protect the circuit from the influence of the peripheral circuit and the deterioration of the insulation performance of the circuit board substrate.
Furthermore, the detection electrode signal SIGA is connected to a common mode interference filtering unit I consisting of R3 and C1 through a connector P1, and then is connected to the pin 1 of the reverse input end of the instrumentation amplifier U1; the detection electrode signal SIGB passes through a connector P1 and then is connected to a second common mode interference filtering unit consisting of R4 and C5, and then is connected to a pin 4 of a non-inverting input end of an instrumentation amplifier U1.
Further, a pin 1 at the inverting input end of the instrumentation amplifier U1 is connected with one end of the resistor R5, and the other end of the resistor R5 is grounded; the 4-pin reverse input end of the instrumentation amplifier U1 is connected with one end of a resistor R6, and the other end of the resistor R6 is grounded; together providing a dc bias loop for instrumentation amplifier U1.
Further, a capacitor C6 is connected between the detection electrode signals SIGA and SIGB for filtering out differential mode interference signals between SIGA and SIGB, and then connected to the inverting input terminal 1 pin and the non-inverting input terminal 4 pin of the U1 of the instrumentation amplifier, respectively.
Further, the gain of the instrumentation amplifier U1 is adjusted by a gain resistor R1, a first end of a resistor R1 is connected to pin 2 of the instrumentation amplifier U1, and a second end of a resistor R1 is connected to pin 3 of the instrumentation amplifier U1; a first terminal of the gain resistor R1 is connected to the non-inverting input terminal pin 3 of the buffer amplifier U2, and a second terminal of the gain resistor R1 is connected to the non-inverting input terminal pin 3 of the buffer amplifier U3.
In one embodiment, pins 1 of the buffer amplifiers U2 and U3 are connected to the abnormality detection unit. The abnormal detection unit collects abnormal voltage through the ADC module and is connected with the main controller; that is, the data is sent to a main controller (such as a microprocessor) for discrimination and processing. And the abnormality detecting unit is a conventional circuit, which is not described herein.
Furthermore, pins 8 and 5 of the instrumentation amplifier U1 are powered by dual power supplies, pin 6 of the instrumentation amplifier U1 provides a reference potential to be connected to a signal ground GND, and pin 7 of the instrumentation amplifier U1 is output through a coupling circuit formed by C2 and R2.
Further, the sensor is of a model FMF-02001621EH12100, the instrumentation amplifier U1 is of a model AD8422, the buffer amplifier U2 is of a model MCP606, and the buffer amplifier U3 is of a model MCP 606.
Compared with the prior art, the utility model has the beneficial effects.
According to the utility model, interference signals are attenuated and filtered through shielding, filtering and signal protection ring technologies, the influence of leakage current of a circuit board substrate is reduced, the signal-to-noise ratio of the electromagnetic flowmeter is effectively improved, the detection of signals of the electromagnetic flowmeter at low flow speed is facilitated, and the flow range ratio is improved.
Drawings
The utility model is further described with reference to the following figures and detailed description. The scope of the utility model is not limited to the following expressions.
Fig. 1 is a circuit diagram of a signal processing circuit in an embodiment.
Detailed Description
As shown in fig. 1, the present embodiment 1 includes a sensor, a double shielded cable, a connector P1, a pre-filter circuit, shielded cable driving circuits U2 and U3, signal protection ring circuits GRA and GRB, an abnormality detection circuit, an instrumentation amplifier circuit U1, and a gain control R1.
1. A signal processing circuit for improving the signal-to-noise ratio of an electromagnetic flowmeter, which is used for an electromagnetic flowmeter for measuring the flow rate of a fluid flowing through a sensor by performing signal processing on flow rate signals detected by a pair of detection electrodes arranged in the sensor and input from a first flow rate signal input terminal and a second flow rate signal input terminal by the signal processing circuit; and an abnormality detection circuit detects an abnormality of the flow rate signal based on an output signal obtained by the signal amplification circuit.
2. The sensor includes: excitation coils L1 and L2, detection electrodes SIGA and SIGB, and ground electrode SG. The detection electrode signals SIGA and SIGB are respectively connected to 1# and 4# of the connector P1 through two inner core wires of the double-shielded cable. The grounding electrode SG is connected to the outer shielding layer of the double shielded cable, then connected to # 5 of P1 of the connector, and connected to the signal ground GND of the detection circuit after passing through the connector P1. The inner shields SA, SB of the double shielded cable are connected to 2#, 3# of the connector P1, respectively.
3. After passing through a connector P1, the SIGA signal is connected to a common mode interference filter circuit consisting of R3 and C1, and then is connected to the 1# inverting input end of an instrumentation amplifier U1. The SIGB signal is connected to a common mode interference filter circuit consisting of R4 and C5, and then is connected to the non-inverting input terminal 4# of an instrumentation amplifier U1. The resistors R5 and R6 are respectively connected to the inverting input terminal 1# and the non-inverting input terminal 4# of the instrumentation amplifier U1, and provide a weak dc bias loop for the instrumentation amplifier U1. The capacitor C6 filters differential mode interference signals between the SIGA and the SIGB, and then is connected to the inverting input end 1# and the non-inverting input end 4# of the U1 of the instrumentation amplifier.
4. The resistor R1 is connected between gain control pins RG, 2#, 3# of the instrumentation amplifier U1, the gain of the instrumentation amplifier U1 can be controlled by adjusting the resistance value of R1, and the gain is usually controlled to be about 10 times because the polarization voltage has a large variation range. Signals with the same potential as the 1# reverse input end and the 4# non-reverse input end of the instrumentation amplifier U1 are respectively led out from the two ends of the gain resistor R1 to the 3# non-reverse input ends of the buffer amplifiers U2 and U3. This may reduce the effect on the input signal to instrumentation amplifier U1. After passing through the buffer amplifiers U2 and U3, the 1# output signals to the abnormality detection unit, respectively, to detect the emptying of the fluid in the pipe, the non-liquid-contact state of the detection electrodes, or the disconnection of the signal lines. The output levels of U2 and U3 deviate from the normal range, and the control circuit is notified of the deviation and the abnormality processing is performed. Meanwhile, after passing through the buffer amplifiers U2 and U3, the 1# outputs a buffer signal with the same potential as the input signal and low impedance to the protection ring circuits GRA and GRB respectively, and surrounds the circuit from the 1# and the 4# of the connector P1 to the reverse input end 1# and the non-reverse input end 4# of the instrumentation amplifier U1 respectively, so as to protect the circuit from the influence of peripheral circuits and the influence of the insulation performance degradation of a circuit board substrate. The buffer signals connected to the guard ring circuits GRA and GRB are also connected to the two inner shields SA and SB of the double shielded cable respectively through 2# and 3# of the connector P1, and the potentials on the two inner shields SA and SB are equal to the potentials between the corresponding core wires respectively by using the driving cable technology, so that the attenuation of the flow signal and the influence of external interference noise caused by the parasitic capacitance between the SIGA and SIGB signals are reduced.
5. The instrumentation amplifier U1 is powered by + Vs (8 #), -Vs (5 #), and 6# of U1 provides a reference potential to be connected to a signal ground GND, and can output a bipolar signal to a subsequent amplifying, filtering and collecting processing circuit through a coupling circuit consisting of C2 and R2.
It should be understood that the detailed description of the present invention is only for illustrating the present invention and is not limited by the technical solutions described in the embodiments of the present invention, and those skilled in the art should understand that the present invention can be modified or substituted equally to achieve the same technical effects; as long as the use requirements are met, the method is within the protection scope of the utility model.
Claims (9)
1. A signal processing system for improving the signal-to-noise ratio of an electromagnetic flowmeter comprises an electromagnetic flow sensor; the method is characterized in that: two output electrode signals of the sensor pass through the double-shielded cable and then respectively pass through respective common-mode interference filtering units and then are connected with the input end of an instrumentation amplifier U1, and the instrumentation amplifier U1 is also respectively connected with a first buffer U2 and a second buffer U3; the output of the first buffer U2 buffers signals to the guard ring GRA and the output of the second buffer U3 buffers signals to the guard ring GRB; the buffered signals connected to the guard ring circuits GRA, GRB are also connected to the inner shields SA, SB of the double shielded cable, respectively.
2. A signal processing system for improving signal-to-noise ratio of an electromagnetic flowmeter according to claim 1, wherein: the sensor comprises excitation coils L1 and L2, detection electrodes SIGA and SIGB, and a grounding electrode SG; wherein, the detection electrode signals SIGA and SIGB are respectively connected to the 1 pin and the 4 pin of the connector P1 through two inner core wires of the double-shielded cable; the grounding electrode SG is connected to an outer shielding layer of the double-shielded cable, then is connected to a pin 5 of a connector P1, passes through a connector P1 and then is connected to a signal ground end GND; the inner shields SA, SB of the double shielded cable are connected to pins 2, 3 of the connector P1, respectively.
3. A signal processing system for improving signal-to-noise ratio of an electromagnetic flowmeter according to claim 1, wherein: the guard ring circuits GRA and GRB surround the circuit from the pins 1 and 4 of the connector P1 to the pins 1 and 4 of the inverting input terminal of the instrumentation amplifier U1, respectively, and protect the circuit from the influence of peripheral circuits and the deterioration of the insulating property of the circuit board substrate.
4. A signal processing system for improving signal-to-noise ratio of an electromagnetic flowmeter according to claim 1, wherein: the detection electrode signal SIGA is connected to a common mode interference filtering unit I consisting of R3 and C1 through a connector P1 and then is connected to a pin 1 at the reverse input end of an instrumentation amplifier U1; the detection electrode signal SIGB passes through a connector P1 and then is connected to a second common mode interference filtering unit consisting of R4 and C5, and then is connected to a pin 4 of a non-inverting input end of an instrumentation amplifier U1.
5. A signal processing system for improving signal-to-noise ratio of an electromagnetic flowmeter according to claim 1, wherein: a pin 1 at the reverse input end of the instrument amplifier U1 is connected with one end of a resistor R5, and the other end of the resistor R5 is grounded; the 4-pin reverse input end of the instrumentation amplifier U1 is connected with one end of a resistor R6, and the other end of the resistor R6 is grounded; together providing a dc bias loop for instrumentation amplifier U1.
6. A signal processing system for improving signal-to-noise ratio of an electromagnetic flowmeter according to claim 1, wherein: the capacitor C6 is connected between the detection electrode signals SIGA and SIGB, is used for filtering out differential mode interference signals between SIGA and SIGB, and is then respectively connected with the inverting input terminal pin 1 and the non-inverting input terminal pin 4 of the U1 of the instrumentation amplifier.
7. A signal processing system for improving signal-to-noise ratio of an electromagnetic flowmeter according to claim 1, wherein: the gain of the instrument amplifier U1 is adjusted by a gain resistor R1, the first end of the resistor R1 is connected with the 2 pin of the instrument amplifier U1, and the second end of the resistor R1 is connected with the 3 pin of the instrument amplifier U1; a first terminal of the gain resistor R1 is connected to the non-inverting input terminal pin 3 of the buffer amplifier U2, and a second terminal of the gain resistor R1 is connected to the non-inverting input terminal pin 3 of the buffer amplifier U3.
8. A signal processing system for improving signal-to-noise ratio of an electromagnetic flowmeter according to claim 1, wherein: the 8 pins and the 5 pins of the instrumentation amplifier U1 are powered by double power supplies, the 6 pin of the instrumentation amplifier U1 provides a reference potential to be connected to a signal ground GND, and the 7 pin of the instrumentation amplifier U1 is output through a coupling circuit formed by C2 and R2.
9. A signal processing system for improving signal-to-noise ratio of an electromagnetic flowmeter according to claim 1, wherein: the sensor is in a model of FMF-02001621EH12100, the instrumentation amplifier U1 is in a model of AD8422, the buffer amplifier U2 is in a model of MCP606, and the buffer amplifier U3 is in a model of MCP 606.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202122119175.2U CN215639606U (en) | 2021-09-03 | 2021-09-03 | Signal processing system for improving signal-to-noise ratio of electromagnetic flowmeter |
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| CN202122119175.2U CN215639606U (en) | 2021-09-03 | 2021-09-03 | Signal processing system for improving signal-to-noise ratio of electromagnetic flowmeter |
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| CN215639606U true CN215639606U (en) | 2022-01-25 |
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| CN202122119175.2U Active CN215639606U (en) | 2021-09-03 | 2021-09-03 | Signal processing system for improving signal-to-noise ratio of electromagnetic flowmeter |
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