Signal processing system for magnetostrictive level gauges

Abstract

This invention provides a signal processing system for a magnetostrictive level gauge, relating to the field of signal processing technology. The system includes a pulse current generator, a waveguide wire, a receiving coil, a signal amplification circuit, a signal amplitude filter, a signal pulse width filter, and a processing chip with a high-speed timer function. The pulse current generator applies a pulse current to the waveguide wire; the waveguide wire generates a torsional wave signal when the pulse current is applied; the receiving coil generates an induced voltage pulse signal in response to the torsional wave signal; the signal amplification circuit amplifies the signal; the signal amplitude filter performs amplitude filtering on the signal; the signal pulse width filter performs pulse width filtering on the signal; and the processing chip with the high-speed timer function measures the propagation time of the torsional wave signal based on the received signal. This system can accurately measure the propagation time of the torsional wave, ensuring the measurement accuracy of the magnetostrictive level gauge.

Description

Technical Field

[0001] This invention relates to the field of signal processing technology, and more specifically to a signal processing system for a magnetostrictive level gauge. Background Technology

[0002] A magnetostrictive level gauge is an instrument that measures the displacement and distance of an object based on the magnetostrictive Widmann effect. Its specific principle is as follows: a pulsed current is applied to a cylindrical magnetostrictive material (waveguide wire), which generates a magnetic field along the axial direction. A circumferential magnetic field (generated by a ring-shaped permanent magnet) is superimposed in the direction perpendicular to the axis. When the two magnetic fields meet, a stress torsional wave is generated (Widmann effect). This torsional wave propagates along the waveguide wire at the speed of sound. When the torsional wave reaches the receiving coil, an induced voltage pulse signal is generated in the coil according to the inverse effect of magnetostriction. Since the speed of the torsional wave is known, the displacement of the ring-shaped permanent magnet can be measured by measuring the propagation time of the torsional wave.

[0003] Typically, the pulse current generator and receiving coil are located in the same position. The pulse current propagates at ultra-high speed to the ring permanent magnet, generating a torsional wave that returns at the speed of sound to the receiving coil. Therefore, the propagation time of the pulse current can be ignored. By measuring the time difference between the generation of the pulse current and the arrival of the torsional wave voltage signal at the receiving coil, i.e., the propagation time of the torsional wave, the displacement of the permanent magnet can be determined. Inaccurate measurement of the torsional wave propagation time directly leads to inaccurate measurement results of the permanent magnet displacement. Therefore, high-precision measurement of the torsional wave propagation time is crucial to ensuring the accuracy of permanent magnet displacement measurement. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of the prior art by providing a signal processing system for a magnetostrictive level gauge, thereby solving the problem of high-precision measurement of torsional wave propagation time.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] This invention provides a signal processing system for a magnetostrictive level gauge, the system comprising a pulse current generator, a waveguide wire, a receiving coil, a signal amplification circuit, a signal amplitude filter, a signal pulse width filter, and a processing chip with a high-speed timer function;

[0007] A pulsed current generator is used to apply a pulsed current to a waveguide wire;

[0008] Waveguide wires are used to generate torsional wave signals when a pulsed current is applied and to propagate the torsional wave signals to the receiving coil;

[0009] The receiving coil is used to generate an induced voltage pulse signal in response to the received torsional wave signal, and transmits the induced voltage pulse signal to the signal amplification circuit;

[0010] The signal amplification circuit is used to amplify the received induced voltage pulse signal, and the amplified signal is transmitted to the signal amplitude filter.

[0011] The signal amplitude filter is used to filter the amplitude of the received signal to remove interference signals with amplitude values ​​smaller than the preset filter amplitude value, and then transmits the amplitude-filtered signal to the signal pulse width filter.

[0012] The signal pulse width filter is used to filter the received signal to remove interference signals with pulse widths smaller than the preset time width, and then transmits the pulse width filtered signal to the processing chip with a high-speed timer function.

[0013] The processing chip with a high-speed timer function is used to measure the propagation time of the torsional wave signal based on the received signal. The processing chip with a high-speed timer function also includes a first signal generator and a second signal generator. The first signal generator is used to generate a pulse signal applied to the pulse current generator, and the second signal generator is used to generate a square wave signal applied to the signal pulse width filter.

[0014] Optionally, the pulse current generator includes a transistor. A pulse signal generated by a first signal generator is applied to the gate of the transistor, and then a pulse current is applied to the waveguide wire via the transistor. The frequency of the pulse signal is 200 Hz and the pulse width is 5 μS.

[0015] Optionally, the signal amplitude filter includes a comparator and a first resistor and a second resistor. The first resistor and the second resistor are connected in series, and the end of the first resistor not connected to the second resistor is connected to a 5V DC voltage. The end of the second resistor not connected to the first resistor is grounded. The connection end of the first resistor and the second resistor is simultaneously connected to the negative terminal of the comparator. The positive terminal of the comparator is connected to the output terminal of the signal amplification circuit. The preset filter amplitude is determined by the resistance values ​​of the first resistor and the second resistor.

[0016] Optionally, the signal pulse width filter includes a first high-speed counter, a first NAND gate, a second NAND gate, a third NAND gate, a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor. The output terminal of the signal amplitude filter is connected to the first input terminal of the first NAND gate, the second input terminal of the first NAND gate is connected to the reset signal output terminal of the processing chip, and the signal from the reset signal output terminal is used to reset the signal pulse width filter. The output terminal of the first NAND gate is connected to the second input terminal of the second NAND gate, the first input terminal of the second NAND gate is connected to a 3V DC voltage, and the output terminal of the second NAND gate is connected to the first input terminal of the first high-speed counter. The first output terminal is connected to one end of the third resistor, the second output terminal of the first high-speed counter is connected to one end of the fourth resistor, the third output terminal of the first high-speed counter is connected to one end of the fifth resistor, the fourth output terminal of the first high-speed counter is connected to one end of the sixth resistor, and one of the other ends of the third, fourth, fifth, and sixth resistors that are not connected to the first high-speed counter is connected to the second input terminal of the third NAND gate. The first input terminal of the third NAND gate is connected to a 3V DC voltage. The processing chip includes a second high-speed timer, and the output terminal of the third NAND gate is connected to the second input terminal of the first high-speed counter and the input terminal of the second high-speed timer.

[0017] Optionally, the second high-speed timer is triggered after the pulse current generator generates a pulse current for 36μS to filter out interference generated by the pulse current. The signal from the output of the third NAND gate is used to trigger the second high-speed timer to stop timing on the down-edge.

[0018] Optionally, the second signal generator is used to generate a 1MHz square wave signal as a clock signal applied to the first high-speed counter.

[0019] The beneficial effects of this invention include:

[0020] The signal processing system for a magnetostrictive level gauge provided by this invention includes a pulse current generator, a waveguide wire, a receiving coil, a signal amplification circuit, a signal amplitude filter, a signal pulse width filter, and a processing chip with a high-speed timer function. The pulse current generator applies a pulse current to the waveguide wire. The waveguide wire generates a torsional wave signal when the pulse current is applied and propagates the torsional wave signal to the receiving coil. The receiving coil generates an induced voltage pulse signal in response to the received torsional wave signal and transmits the induced voltage pulse signal to the signal amplification circuit. The signal amplification circuit amplifies the received induced voltage pulse signal and transmits the amplified signal to the signal amplitude filter. The signal amplitude filter further amplifies the received signal. An amplitude filter is used to remove interference signals with amplitude values ​​smaller than a preset filter amplitude. The amplitude-filtered signal is then transmitted to a signal pulse width filter. The signal pulse width filter further filters the received signal to remove interference signals with pulse widths smaller than a preset time width. The pulse width-filtered signal is then transmitted to a processing chip with a high-speed timer function. This processing chip measures the propagation time of the torsional wave signal based on the received signal. The processing chip also includes a first signal generator and a second signal generator. The first signal generator generates a pulse signal applied to a pulse current generator, and the second signal generator generates a square wave signal applied to the signal pulse width filter. This system can accurately measure the propagation time of the torsional wave, ensuring the measurement accuracy of the magnetostrictive level gauge. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A structural block diagram of a signal processing system for a magnetostrictive level gauge provided in an embodiment of the present invention is shown.

[0023] Figures 2A to 2C A circuit diagram of a signal processing system for a magnetostrictive level gauge provided in an embodiment of the present invention is shown.

[0024] Figure 3 The diagram shows the signal measurement results of the signal processing system for a magnetostrictive level gauge provided in an embodiment of the present invention.

[0025] Figure 4A flowchart of the signal processing system for a magnetostrictive level gauge provided in an embodiment of the present invention is shown. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] A magnetostrictive level gauge is an instrument that measures the displacement and distance of an object based on the magnetostrictive Widmann effect. Its specific principle is as follows: a pulsed current is applied to a cylindrical magnetostrictive material (waveguide wire), generating a magnetic field along the axis. A circumferential magnetic field (generated by a ring-shaped permanent magnet) is superimposed in the direction perpendicular to the axis. When the two magnetic fields meet, a stress torsional wave is generated (Widmann effect). This torsional wave propagates along the waveguide wire at the speed of sound. When the torsional wave reaches the receiving coil, according to the inverse effect of magnetostriction, an induced voltage pulse signal is generated in the coil. Since the speed of the torsional wave is known, the displacement of the ring-shaped permanent magnet can be measured by measuring the propagation time of the torsional wave. Typically, the pulsed current generator and the receiving coil are located in the same position. The pulsed current propagates to the ring-shaped permanent magnet at the speed of light, and then generates a torsional wave that returns to the receiving coil at the speed of sound. Therefore, the propagation time of the pulsed current can be ignored. The displacement of the permanent magnet can be determined by measuring the time difference between the generation of the pulsed current and the arrival of the torsional wave voltage signal at the receiving coil. This invention addresses the signal processing problem of magnetostrictive level gauges by proposing a high-precision torsional wave timing measurement system.

[0028] Figure 1 A structural block diagram of a signal processing system for a magnetostrictive level gauge provided in an embodiment of the present invention is shown. Figures 2A to 2C A circuit diagram of a signal processing system for a magnetostrictive level gauge provided in an embodiment of the present invention is shown.

[0029] like Figure 1 As shown, the signal processing system for a magnetostrictive level gauge provided by the present invention includes a pulse current generator 101, a waveguide wire 102, a receiving coil 103, a signal amplification circuit 104, a signal amplitude filter 105, a signal pulse width filter 106, and a processing chip 107 with a high-speed timer function, which is also known as an MCU.

[0030] The pulse current generator 101 is used to apply a pulse current to the waveguide wire 102. Optionally, the pulse current generator 101 includes a transistor, and a pulse signal generated by a first signal generator is applied to the gate of the transistor, and then a pulse current is applied to the waveguide wire 102 via the transistor. The frequency of the pulse signal is 200 Hz and the pulse width is 5 μS.

[0031] Figure 2A This is a circuit diagram showing the connection between the pulse current generator 101 and the waveguide wire 102. Figure 2A In the diagram, P3 represents the waveguide wire, which is subjected to a pulsed current through transistor Q1. The pulse signal is generated by the MCU (i.e., the processing chip 107 with a high-speed timer function), with a frequency of 200Hz and a pulse width of 5μS. The pin MCU 5uS 200Hz represents the first signal generator of the MCU.

[0032] Waveguide wire 102 is used to generate a torsional wave signal when a pulsed current is applied, and to propagate the torsional wave signal to receiving coil 103. Receiving coil 103 is used to generate an induced voltage pulse signal in response to the received torsional wave signal, and to transmit the induced voltage pulse signal to signal amplification circuit 104. Figure 2B This is a circuit diagram showing the connection relationship between the receiving coil 103, the signal amplification circuit 104, the signal amplitude filter 105, and the signal pulse width filter 106. (See diagram for example.) Figure 2B In the diagram, P1 represents the receiving coil 103, which receives the torsional wave signal and sends it to the signal amplifier U1 (i.e., the signal amplifier circuit 104) for amplification. The resistor R36 can adjust the amplification factor.

[0033] The signal amplification circuit 104 amplifies the received induced voltage pulse signal and transmits the amplified signal to the signal amplitude filter 105. Optionally, the signal amplitude filter 105 includes a comparator, a first resistor, and a second resistor. The first and second resistors are connected in series, with the end of the first resistor not connected to the second resistor connected to a 5V DC voltage, and the end of the second resistor not connected to the first resistor grounded. The connection terminals of the first and second resistors are simultaneously connected to the negative terminal of the comparator, and the positive terminal of the comparator is connected to the output terminal of the signal amplification circuit. The preset filter amplitude is determined by the resistance values ​​of the first and second resistors.

[0034] Specifically, such as Figure 2B As shown, the amplified signal enters the amplitude filter (i.e., signal amplitude filter 105) composed of comparator U6A and resistors R26 and R16. Its function is to filter out interference with small amplitude values, and the filter amplitude is set according to the voltage division of R26 and R16.

[0035] Signal amplitude filter 105 is used to perform amplitude filtering on the received signal to filter out interference signals with amplitude values ​​smaller than a preset filtering amplitude value, and transmits the amplitude-filtered signal to signal pulse width filter 106. Signal pulse width filter 106 is used to perform pulse width filtering on the received signal to filter out interference signals with pulse widths smaller than a preset time width, and transmits the pulse width-filtered signal to processing chip 107 with high-speed timer function. Processing chip 107 with high-speed timer function is used to measure the propagation time of the torsional wave signal based on the received signal. Processing chip 107 with high-speed timer function also includes a first signal generator and a second signal generator. The first signal generator is used to generate a pulse signal applied to the pulse current generator, and the second signal generator is used to generate a square wave signal applied to the signal pulse width filter.

[0036] Optionally, the signal pulse width filter 106 includes a first high-speed counter, a first NAND gate, a second NAND gate, a third NAND gate, a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor. The output terminal of the signal amplitude filter is connected to the first input terminal of the first NAND gate, the second input terminal of the first NAND gate is connected to the reset signal output terminal of the processing chip, and the signal from the reset signal output terminal is used to reset the signal pulse width filter. The output terminal of the first NAND gate is connected to the second input terminal of the second NAND gate, the first input terminal of the second NAND gate is connected to a 3V DC voltage, and the output terminal of the second NAND gate is connected to the first input terminal of the first high-speed counter. The first output terminal of the first high-speed counter is connected to one end of the third resistor. The second output terminal of the first high-speed counter is connected to one end of the fourth resistor. The third output terminal of the first high-speed counter is connected to one end of the fifth resistor. The fourth output terminal of the first high-speed counter is connected to one end of the sixth resistor. One of the other ends of the third, fourth, fifth, and sixth resistors that are not connected to the first high-speed counter is connected to the second input terminal of the third NAND gate. The first input terminal of the third NAND gate is connected to a 3V DC voltage. The processing chip includes a second high-speed timer. The output terminal of the third NAND gate is connected to the second input terminal of the first high-speed counter and the input terminal of the second high-speed timer. Optionally, the second high-speed timer is triggered after a pulse current generator generates a 36μS pulse current to filter out interference generated by the pulse current. The signal from the output terminal of the third NAND gate is used to trigger the second high-speed timer to stop counting on the down-edge. Optionally, the second signal generator is used to generate a 1MHz square wave signal as a clock signal applied to the first high-speed counter.

[0037] Specifically, such as Figure 2BAs shown, the signal after amplitude filtering enters the pulse width filter (i.e., signal pulse width filter 106) composed of NAND gates U11B, U11B, U11D and high-speed counter U18. A 1MHz square wave (generated by the second signal generator) is generated by the MCU as the clock signal and enters the counter U18. When U6A outputs a 5V high level, U18 starts counting according to the clock signal. Its outputs are Q1, Q2, Q3, and TC pins, corresponding to the count values ​​1, 2, 4, and 8, in μS. By arbitrarily selecting a pin and inputting NAND gate U11B, the counter U18 can enter the hold mode, and the output pin will no longer toggle. This can filter out interference that is shorter than the set time width. Resistors R64A, R64B, R64C, and R64D are used to set the filtering time, and one of them can be used. Figure 2C This is a pin diagram of the processing chip 107 with a high-speed timer function, as shown below. Figure 2C As shown, the MCUcounter pin enters the MCU (i.e., the processing chip 107 with high-speed timer function), triggering the MCU's high-speed timer to stop counting on the down-curving edge. The MCU's high-speed timer is used to measure the propagation time of the torsional wave, and its start is triggered 36μS after the generation of a pulse current to filter out interference generated by the pulse current. The MCU reset pin is used to reset the pulse width filter (i.e., the signal pulse width filter 106).

[0038] Figure 3 The diagram shows the signal measurement results of the signal processing system for a magnetostrictive level gauge provided in an embodiment of the present invention. Figure 3 As shown, curve 1 represents a 5μS pulse current, and curve 2 is the amplified signal. The spike on the left side of the signal is interference caused by the pulse current and should be filtered out. The spike on the right side of the signal is a torsional wave signal. By measuring the time difference between it and the pulse current, the displacement of the permanent magnet can be determined. In actual use of level gauges, there will be many interferences. Filtering can be performed on the signal amplitude, width, and time correlation.

[0039] In summary, this system generates a torsional wave signal through a waveguide wire when a pulsed current is applied. The receiving coil then generates an induced voltage pulse signal in response to the received torsional wave signal. The signal is then amplified, amplitude-filtered, and pulse-width filtered. Finally, a processing chip measures the propagation time of the torsional wave signal. The same processing chip handles the generation of the pulsed current signal, the square wave signal used for pulse-width filtering, the signal reception, and the measurement of propagation time. Therefore, the propagation time of the torsional wave can be accurately measured, ensuring the measurement accuracy of the magnetostrictive level gauge.

[0040] The workflow of the magnetostrictive level gauge signal processing system consists of: Figure 4The following pins are provided: MCU 5μS 200Hz represents the MCU's first signal generator, used to generate a pulse current with a pulse width of 5μS and a frequency of 200Hz. MCU 1MHz represents the MCU's second signal generator, generating a clock signal with a frequency of 1MHz, used for pulse width filtering. MCU counter represents the MCU's second high-speed timer, used for external timing to measure the propagation time of a torsional wave, with a resolution of 0.05μS. Given that the propagation speed of a torsional wave is 2777m / s, and the time to detect a 1mm length is 0.36μS, to eliminate interference caused by the pulse current, the MCU's high-speed timer starts timing 36μS after generating the pulse current. The falling edge of the MCU counter pin triggers the MCU's second high-speed timer to stop timing.

[0041] Optionally, the system can also load a correlation filtering algorithm. Correlation filtering considers that under the same measurement conditions, interference is randomly generated, while the signal is constant. Therefore, for the propagation time values ​​of five consecutively recorded torsional waves, the two closest values ​​are taken, and their average is calculated to filter out random interference. The output measurement results are displacement L in mm, torsional wave propagation time t in μS, pulse width filtering length n in μS, and torsional wave propagation velocity 2.777 mm / μS. The displacement calculation formula is:

[0042] L = (t + 36 - n) × 2.777.

[0043] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A signal processing system for a magnetostrictive level gauge, characterized in that, The system includes a pulse current generator, a waveguide wire, a receiving coil, a signal amplification circuit, a signal amplitude filter, a signal pulse width filter, and a processing chip with a high-speed timer function; The pulse current generator is used to apply a pulse current to the waveguide wire; The waveguide wire is used to generate a torsional wave signal when a pulsed current is applied, and to propagate the torsional wave signal to the receiving coil; The receiving coil is used to generate an induced voltage pulse signal in response to the received torsional wave signal, and transmit the induced voltage pulse signal to the signal amplification circuit; The signal amplification circuit is used to amplify the received induced voltage pulse signal, and the amplified signal is transmitted to the signal amplitude filter. The signal amplitude filter is used to perform amplitude filtering on the received signal to filter out interference signals with amplitude values ​​smaller than a preset filtering amplitude value, and transmit the amplitude-filtered signal to the signal pulse width filter. The signal pulse width filter is used to perform pulse width filtering on the received signal to filter out interference signals with pulse widths smaller than the preset time width, and transmit the pulse width filtered signal to the processing chip with high-speed timer function. The processing chip with a high-speed timer function is used to measure the propagation time of the torsional wave signal based on the received signal. The processing chip with a high-speed timer function also includes a first signal generator and a second signal generator. The first signal generator is used to generate a pulse signal applied to the pulse current generator, and the second signal generator is used to generate a square wave signal applied to the signal pulse width filter.

2. The signal processing system for a magnetostrictive level gauge according to claim 1, characterized in that, The pulse current generator includes a transistor. A pulse signal generated by the first signal generator is applied to the gate of the transistor, and then a pulse current is applied to the waveguide wire via the transistor. The frequency of the pulse signal is 200 Hz and the pulse width is 5 μS.

3. The signal processing system for a magnetostrictive level gauge according to claim 1, characterized in that, The signal amplitude filter includes a comparator, a first resistor, and a second resistor. The first resistor and the second resistor are connected in series. The end of the first resistor not connected to the second resistor is connected to a 5V DC voltage, and the end of the second resistor not connected to the first resistor is grounded. The connection point of the first resistor and the second resistor is simultaneously connected to the negative terminal of the comparator. The positive terminal of the comparator is connected to the output terminal of the signal amplification circuit. The preset filter amplitude is determined by the resistance values ​​of the first resistor and the second resistor.

4. The signal processing system for a magnetostrictive level gauge according to claim 1, characterized in that, The signal pulse width filter includes a first high-speed counter, a first NAND gate, a second NAND gate, a third NAND gate, a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor. The output terminal of the signal amplitude filter is connected to the first input terminal of the first NAND gate. The second input terminal of the first NAND gate is connected to the reset signal output terminal of the processing chip. The signal from the reset signal output terminal is used to reset the signal pulse width filter. The output terminal of the first NAND gate is connected to the second input terminal of the second NAND gate. The first input terminal of the second NAND gate is connected to a 3V DC voltage. The output terminal of the second NAND gate is connected to the first input terminal of the first high-speed counter. The first output terminal of the first high-speed counter is connected to... One end of the third resistor is connected to the first high-speed counter, the second output terminal of the first high-speed counter is connected to one end of the fourth resistor, the third output terminal of the first high-speed counter is connected to one end of the fifth resistor, the fourth output terminal of the first high-speed counter is connected to one end of the sixth resistor, and one of the other ends of the third, fourth, fifth, and sixth resistors that are not connected to the first high-speed counter is connected to the second input terminal of the third NAND gate. The first input terminal of the third NAND gate is connected to a 3V DC voltage. The processing chip includes a second high-speed timer, and the output terminal of the third NAND gate is connected to the second input terminal of the first high-speed counter and the input terminal of the second high-speed timer.

5. The signal processing system for a magnetostrictive level gauge according to claim 4, characterized in that, The second high-speed timer is triggered after the pulse current generator generates a 36μS pulse current to filter out interference generated by the pulse current. The signal from the output of the third NAND gate is used to trigger the second high-speed timer to stop timing on the down-edge.

6. The signal processing system for a magnetostrictive level gauge according to claim 4, characterized in that, The second signal generator is used to generate a 1MHz square wave signal as a clock signal applied to the first high-speed counter.

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