Pulse signal processing circuit and magnetostrictive liquid level meter

Abstract

The invention relates to the technical field of liquid level measurement, in particular to a pulse signal processing circuit and a magnetostrictive liquidometer, and the pulse signal processing circuit comprises an amplitude limiting module which is used for carrying out amplitude limiting processing on a first voltage signal and a second voltage signal transmitted by an induction coil of a magnetostrictive sensor, the first voltage signal is a voltage signal obtained according to an induction pulse signal, and the second voltage signal is a voltage signal obtained according to a strain pulse signal; the signal amplification module is connected with the output of the amplitude limiting module, amplifies the output and outputs the amplified output to a time-to-digital converter of the magnetostriction sensor; according to the pulse signal processing circuit, the interference of the induction pulse signal on the signal processing process of the time-to-digital converter can be well reduced.

Description

Technical Field

[0001] The invention relates to the technical field of liquid level measurement, and in particular to a pulse signal processing circuit and a magnetostrictive liquid level meter. Background Art

[0002] The magnetostrictive level gauge is a precision instrument that uses the magnetostrictive principle to measure the height of the liquid. It usually includes a magnetostrictive sensor, a waveguide wire (waveguide tube), and a float that floats with the liquid surface. A magnet is installed in the float to generate a magnetic ring magnetic field. During the measurement process, a drive pulse (current pulse) signal is regularly generated in the electronic chamber of the magnetostrictive sensor. The drive pulse signal is transmitted along the waveguide wire and generates a circular magnetic field outside the waveguide wire. When the circular magnetic field intersects with the magnetic ring magnetic field, the waveguide wire will deform due to the effect of magnetostriction, thereby generating a strain pulse signal (strain mechanical wave pulse signal), which is transmitted to the magnetostrictive sensor at a fixed speed. The magnetostrictive sensor converts the strain pulse signal into a voltage signal and determines the height of the liquid surface based on the time when the drive pulse signal is sent and the time when the voltage signal is received.

[0003] However, in addition to causing the waveguide wire to deform and thus generate a strain pulse signal, the driving pulse signal will also induce an induced pulse signal (current signal) due to the change in the magnetic field. The induced pulse signal is much larger than the above-mentioned voltage signal, thereby interfering with the strain pulse signal processing process of the magnetostrictive sensor and causing a reduction in measurement accuracy. Summary of the invention

[0004] The present invention provides a pulse signal processing circuit and a magnetostrictive liquid level meter to solve the technical problem in the prior art that an induction pulse signal caused by a driving pulse signal easily interferes with the strain pulse signal processing process of a magnetostrictive sensor, resulting in reduced measurement accuracy.

[0005] A pulse signal processing circuit provided by the present invention is applied to a magnetostrictive liquid level meter. The pulse signal processing circuit comprises: a limiting module and a signal amplification module;

[0006] A limiting module, which is used to perform limiting processing on a first voltage signal and a second voltage signal transmitted by an induction coil of a magnetostrictive sensor, wherein the first voltage signal refers to a voltage signal obtained according to an induction pulse signal, and the second voltage signal refers to a voltage signal obtained according to a strain pulse signal; and

[0007] The signal amplification module is connected to the output of the limiting module and amplifies the output and then outputs it to the time digital converter of the magnetostrictive sensor.

[0008] In one embodiment of the present invention, the pulse signal processing circuit further includes: an induction pulse elimination module, the induction pulse elimination module includes: a controller and an analog switch;

[0009] The controller is used to disconnect the analog switch and start timing when it is determined that the magnetostrictive sensor sends a driving pulse signal. If the accumulated timing reaches a preset time threshold, the analog switch is controlled to be turned on to eliminate the induction pulse signal.

[0010] The controller is respectively connected to the signal input end of the circuit board where the magnetostrictive sensor and the analog switch are located, one end of the analog switch is connected to the output end of the signal amplification module, and the other end of the analog switch is connected to the time-to-digital converter.

[0011] In one embodiment of the present invention, the pulse signal processing circuit further includes: a filtering module, configured to filter the signal output by the analog switch;

[0012] The input end of the filter module is connected to the output end of the analog switch, and the output end of the filter module is connected to the time-to-digital converter.

[0013] In one embodiment of the present invention, the limiting module includes: a first diode and a second diode;

[0014] The anode of the first diode is connected to the negative output end of the induction coil, the cathode of the first diode is connected to the positive output end of the induction coil, the anode of the second diode is connected to the positive output end of the induction coil, and the cathode of the second diode is connected to the negative output end of the induction coil to form a bidirectional limiter, the cathode of the first diode is the negative output end of the limiter module, and the cathode of the second diode is the positive output end of the limiter module.

[0015] In one embodiment of the present invention, the signal amplification module includes: a bias unit, a filter unit, and a signal amplification unit connected in sequence.

[0016] In one embodiment of the present invention, the bias unit includes: a first resistor, a second resistor, and a third resistor, and the filter unit includes: a fourth resistor, a fifth resistor, a first capacitor, a second capacitor, and a third capacitor;

[0017] The first end of the first resistor is connected to the negative electrode of the external power supply, the second end of the first resistor is respectively connected to the first end of the second resistor and the positive output end of the limiting module, the second end of the second resistor is respectively connected to the first end of the third resistor and the negative output end of the limiting module, and the second end of the third resistor is connected to the positive electrode of the external power supply;

[0018] One end of the fourth resistor is connected to the second end of the first resistor, the other end of the fourth resistor, the first capacitor, the second capacitor, and the fifth resistor are connected in sequence, the fifth resistor is connected to the negative output end of the limiting module, there is a grounding node between the first capacitor and the second capacitor, there is a first connection point between the fourth resistor and the first capacitor, there is a second connection point between the fifth resistor and the second capacitor, the first end of the third capacitor is connected to the first connection point, and the second end of the third capacitor is connected to the second connection point; the first end of the third capacitor is connected to the negative input end of the signal amplification unit, and the second end of the third capacitor is connected to the positive input end of the signal amplification unit.

[0019] In one embodiment of the present invention, the signal amplification unit includes: a sixth resistor and an instrumentation amplifier;

[0020] One end of the third capacitor is connected to the positive input terminal of the instrument amplifier, and the other end of the third capacitor is connected to the negative input terminal of the instrument amplifier. The instrument amplifier is externally connected to the sixth resistor, and the resistance of the sixth resistor is inversely proportional to the gain of the instrument amplifier.

[0021] In one embodiment of the present invention, the induction pulse elimination module further includes a noise reduction unit and a bias resistor, and the noise reduction unit includes a seventh resistor and a fourth capacitor;

[0022] One end of the seventh resistor is connected to the output end of the controller, the other end of the seventh resistor is connected to the signal input end of the circuit board where the analog switch is located, one end of the seventh resistor away from the controller is connected to the fourth capacitor, and one end of the fourth capacitor away from the seventh resistor is grounded;

[0023] One end of the bias resistor is connected to the output end of the analog switch, and the other end of the bias resistor is grounded.

[0024] In one embodiment of the present invention, the filtering module includes: an operational amplifier, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a fifth capacitor, and a sixth capacitor;

[0025] One end of the eighth resistor is the input end of the filtering module, the other end of the eighth resistor, the ninth resistor, and the non-inverting input end of the operational amplifier are connected in sequence, one end of the fifth capacitor is connected to the non-inverting input end of the operational amplifier, the other end of the fifth capacitor is grounded, one end of the tenth resistor is connected to the inverting input end of the operational amplifier, the other end of the tenth resistor is grounded, one end of the eleventh resistor is connected to the inverting input end of the operational amplifier, the other end of the eleventh resistor is connected to the output end of the operational amplifier, one end of the sixth capacitor is connected to one end of the eighth resistor close to the ninth resistor, the other end of the sixth capacitor is connected to the output end of the operational amplifier, and the output end of the operational amplifier is the output end of the filtering module.

[0026] The present invention also provides a magnetostrictive liquid level meter, comprising: a pulse signal processing circuit as described in any one of the above items.

[0027] Beneficial effects of the present invention: The pulse signal processing circuit and magnetostrictive liquid level meter provided by the present invention, the pulse signal processing circuit is provided with a limiting module and a signal amplification module, the limiting module is used to perform limiting processing on the first voltage signal and the second voltage signal transmitted by the induction coil of the magnetostrictive sensor, the first voltage signal refers to the voltage signal obtained according to the induction pulse signal, the second voltage signal refers to the voltage signal obtained according to the strain pulse signal, and the signal amplification module is connected to the output of the limiting module, the output of the limiting module is amplified by the signal amplification module and then output to the time digital converter of the magnetostrictive sensor; it can well reduce the interference of the induction pulse signal to the signal processing process of the time digital converter. It can be understood that the first voltage signal corresponding to the induction pulse signal is much larger than the second voltage signal corresponding to the strain pulse signal, so by limiting the voltage signal output by the induction coil, the larger first voltage signal can be clamped within a fixed voltage range, thereby reducing the interference of the first voltage signal / induction pulse signal to the signal processing process of the time digital converter, thereby improving the accuracy of the signal processing of the time digital converter (determining the height of the liquid level according to the time of sending the driving pulse signal and the time of receiving the voltage signal corresponding to the strain pulse signal) to a certain extent.

[0028] Furthermore, since the second voltage signal corresponding to the strain pulse signal is relatively small, the second voltage signal can smoothly pass through the limiting module and enter the signal amplification module. By amplifying the second voltage signal, it can help the subsequent time-to-digital converter to perform signal recognition and processing.

[0029] In addition, compared with directly inputting the first voltage signal and the second voltage signal output by the induction coil into the signal amplification module, the stability and safety of the above-mentioned device provided by the present invention are stronger. It can be understood that since the induction pulse signal is a current signal and the strain pulse signal is a mechanical wave signal, the induction pulse signal reaches the induction coil faster than the strain pulse signal. The induction coil will first convert the induction pulse signal into a first voltage signal, and then convert the later arriving strain pulse signal into a second voltage signal. On this basis, if the first voltage signal generated first is directly input into the signal amplification module, the response time of the signal amplification module to the second voltage signal may be slowed down (after the larger first voltage signal is transmitted into the signal amplification module, the amplifier in the signal amplification module is saturated, and it takes a longer time to recover from the saturated state to the linear state), and the larger first voltage signal is easy to damage the amplifier in the signal amplification module. The pulse signal processing circuit in the present invention can better solve this problem by setting a limiting circuit between the induction coil and the signal amplification module, while reducing the interference of the larger first voltage signal to the signal processing process of the time digital converter, and realizing the amplification of the second voltage signal, so as to help improve the processing accuracy of the time digital converter for the strain pulse signal, and better protect the components in the signal amplification module, thereby improving the stability of the entire circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of the principle of a magnetostrictive sensor provided by an embodiment of the present invention;

[0031] Figure 2 A schematic diagram of a pulse signal processing circuit provided in one embodiment of the present invention;

[0032] Figure 3 Another schematic diagram of the structure of a pulse signal processing circuit provided by an embodiment of the present invention;

[0033] Figure 4 A schematic diagram of the structure of a limiting module and a signal amplifying module in a pulse signal processing circuit provided in one embodiment of the present invention;

[0034] Figure 5 A schematic diagram of the structure of an induction pulse elimination module in a pulse signal processing circuit provided in an embodiment of the present invention;

[0035] Figure 6 The present invention is a schematic diagram of the structure of a filter module in a pulse signal processing circuit provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0037] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0038] In the following description, numerous details are discussed to provide a more thorough explanation of the embodiments of the present invention. However, it is obvious to those skilled in the art that the embodiments of the present invention can be implemented without these specific details. In other embodiments, well-known structures and devices are shown in the form of block diagrams rather than in detail to avoid making the embodiments of the present invention difficult to understand.

[0039] In order to facilitate understanding of the pulse signal processing circuit and the magnetostrictive liquid level meter provided by the present invention, the working principle of the magnetostrictive sensor is explained below.

[0040] Please refer to Figure 1 , the induction coil in the magnetostrictive sensor can be equivalent to an inductor, such as Figure 1 The inductance of the right part of the waveguide can be equivalent to a resistor, such as Figure 1 When the induction pulse signal (current signal) or strain pulse signal is transmitted to the induction coil, the induction coil will convert the induced signal into a voltage signal, which is convenient for the subsequent time-to-digital converter (TDC) to process the signal, that is, to determine the height of the liquid level according to the time when the drive pulse signal is sent and the time when the voltage signal corresponding to the strain pulse signal is received. Figure 1 The arrow in the figure indicates the propagation direction of the signal, I indicates the induction pulse signal, A indicates the strain pulse signal, and V1 indicates the voltage signal obtained by the induction coil by converting the induction pulse signal or the strain pulse signal.

[0041] See also Figure 2 , Figure 2 A schematic diagram of a pulse signal processing circuit according to an embodiment of the present invention is shown in FIG. Figure 2As shown, the pulse signal processing circuit is applied to a magnetostrictive liquid level meter, comprising:

[0042] A limiting module, which is used to perform limiting processing on a first voltage signal and a second voltage signal transmitted by an induction coil of a magnetostrictive sensor, wherein the first voltage signal refers to a voltage signal obtained according to an induction pulse signal, and the second voltage signal refers to a voltage signal obtained according to a strain pulse signal; and

[0043] The signal amplification module is connected to the output of the limiting module and amplifies the output and then outputs it to the time digital converter of the magnetostrictive sensor.

[0044] It should be noted that the input end of the limiting module is connected to the induction coil, the output end of the limiting module is connected to the input end of the signal amplification module, and the output end of the signal amplification module is connected to the time-to-digital converter of the magnetostrictive sensor.

[0045] It can be understood that a driving pulse signal is regularly generated in the electronic chamber of the magnetostrictive sensor, and the driving pulse signal is transmitted along the waveguide wire and generates a circumferential magnetic field outside the waveguide wire. When the circumferential magnetic field intersects with the magnetic ring magnetic field of the float, an induction pulse signal is generated due to the change in the magnetic field. In addition, due to the effect of magnetostriction, the waveguide wire will be deformed, thereby generating a strain pulse signal. The propagation speed of the induction pulse signal is faster than that of the strain pulse signal, so the induction pulse signal and the strain pulse signal are successively returned to the induction coil via the waveguide wire. When the induction coil detects the induction pulse signal, the induction pulse signal is converted into a first voltage signal. When the induction coil detects the strain pulse signal, the strain pulse signal is converted into a second voltage signal. The first voltage signal and the second voltage signal are both transmitted to the time-to-digital converter of the magnetostrictive sensor for signal processing to achieve liquid level measurement. The time-to-digital converter determines the height of the liquid level based on the time when the driving pulse signal is sent and the time when the voltage signal corresponding to the strain pulse signal is received.

[0046] It should be noted that, by setting a limiting module, the amplitude of the voltage signal input to the signal amplification module can be limited to prevent the amplifier (i.e., instrument amplifier) ​​in the signal amplification module from entering a saturated state, so as to ensure the response speed of the signal amplification module to the second pulse signal. In addition, it is effectively prevented that the high voltage (first voltage signal) causes damage to the amplifier. In addition, the limiting module can clamp the first voltage signal within a fixed voltage range, thereby reducing the interference of the first voltage signal with the subsequent processing of the time-to-digital converter.

[0047] It should also be noted that, by providing a signal amplification module, the second voltage signal after limiting can be amplified, thereby facilitating signal recognition and processing by the time-to-digital converter of the magnetostrictive sensor.

[0048] It is understandable that although the first voltage signal still enters the signal amplification module for amplification after being limited by the limiting module, the amplified signal is still lower than the original first voltage signal, thereby reducing the interference of the first voltage signal on the signal processing process of the time-to-digital converter.

[0049] In order to further eliminate the interference of the induction pulse signal on the signal processing process of the time digital converter and to reduce the signal noise, the induction pulse elimination module and the filtering module are introduced in turn in the following embodiment. The connection relationship between the various circuits can be referred to Figure 3 .like Figure 3 As shown, the induction coil, the limiting module, the signal amplification module, the induction pulse elimination module, the filtering module, and the time-to-digital converter are connected in sequence.

[0050] In some embodiments, the pulse signal processing circuit further includes: an induction pulse elimination module, and the induction pulse elimination module includes: a controller and an analog switch.

[0051] The controller is used to disconnect the analog switch and start timing when it is determined that the magnetostrictive sensor sends a driving pulse signal. If the accumulated timing reaches a preset time threshold, the analog switch is controlled to be turned on to eliminate the induction pulse signal.

[0052] The controller is respectively connected to the signal input end of the circuit board where the magnetostrictive sensor and the analog switch are located, one end of the analog switch is connected to the output end of the signal amplification module, and the other end of the analog switch is connected to the time-to-digital converter.

[0053] It should be noted that, since the induction pulse signal is a current signal and the strain pulse signal is a mechanical wave signal, the induction pulse signal reaches the induction coil faster than the strain pulse signal. Therefore, by setting the above-mentioned induction pulse elimination module between the signal amplification module and the time-to-digital converter, the induction pulse signal can be eliminated. The time threshold can be determined according to the difference between the time when the induction pulse signal is transmitted to the induction coil and the time when the strain pulse signal is transmitted to the induction coil. For example: Assuming that the difference between the time when the induction pulse signal is transmitted to the induction coil and the time when the strain pulse signal is transmitted to the induction coil is 20 microseconds (the time when the drive pulse signal is transmitted to the float is faster, which can be ignored here), then the time threshold can be 20 microseconds, etc. It can be understood that when the electronic chamber of the magnetostrictive sensor sends a drive pulse signal, the controller of the induction pulse elimination module controls the analog switch to be disconnected, then the induction pulse signal that arrives first (the induction pulse signal after limiting and signal amplification) cannot pass through the analog switch and is eliminated. After 20 microseconds, the controller controls the analog switch to be turned on, and the strain pulse signal arriving at this time (the strain pulse signal after amplitude limiting and signal amplification) can directly pass through the analog switch.

[0054] The induction pulse elimination module in the above embodiment can effectively eliminate the induction pulse signal, avoid interfering with the signal processing process of the time-to-digital converter, and prevent the time-to-digital converter from being triggered by mistake.

[0055] In some embodiments, the pulse signal processing circuit further includes: a filtering module, configured to filter the signal output by the analog switch.

[0056] The input end of the filter module is connected to the output end of the analog switch, and the output end of the filter module is connected to the time-to-digital converter.

[0057] It should be noted that, by providing the above-mentioned filtering module, noise and burrs in the signal can be eliminated, thereby helping to improve the signal processing accuracy of the subsequent time-to-digital converter.

[0058] Figure 4 For a structural diagram of a limiting module and a signal amplification module in a pulse signal processing circuit provided in an embodiment of the present invention, please refer to Figure 4 In some embodiments, the limiting module includes: a first diode D1 and a second diode D2.

[0059] The anode of the first diode D1 is connected to the negative output end (MRX-) of the induction coil, the cathode of the first diode D1 is connected to the positive output end of the induction coil, the anode of the second diode D2 is connected to the positive output end (MRX+) of the induction coil, and the cathode of the second diode D2 is connected to the negative output end of the induction coil to form a bidirectional limiter, the cathode of the first diode D1 is the negative output end of the limiter module, and the cathode of the second diode D2 is the positive output end of the limiter module.

[0060] It should be noted that the first diode D1 and the second diode D2 are both limiting diodes. Based on the unidirectional conduction characteristics of the diode, when the signal output by the induction coil is a positive voltage signal, the second diode D2 is turned on, and the first diode D1 is in a reverse cut-off state, so the voltage passing through the second diode D2 is clamped / limited within the conduction voltage of the second diode D2, that is, the maximum value of the voltage signal output by it will not exceed the conduction voltage of the second diode D2. When the signal output by the induction coil is a negative voltage signal, the first diode D1 is turned on, and the second diode D2 is in a reverse cut-off state, so the voltage passing through the first diode D1 is clamped / limited within the reverse breakdown voltage of the first diode D1, that is, the maximum value of the voltage signal output by it will not exceed the reverse breakdown voltage of the first diode D1. For example, assuming that the on-state voltage of the second diode D2 is 0.2V and the reverse breakdown voltage of the first diode D1 is -0.2V, the voltage signal output from the limiting module will be clamped within [-0.2V, 0.2V], which is the limiting range of the limiting module.

[0061] It should be mentioned that the useful signal of the strain pulse signal is within the limiting range of the limiting module. After the strain pulse signal is converted into the second voltage signal, the useful signal contained therein is usually about 100mV (millivolts), and the limiting range of the limiting module can be set based on the value of the second voltage signal to avoid distortion of the useful signal.

[0062] In some embodiments, the signal amplification module includes: a bias unit, a filtering unit, and a signal amplification unit connected in sequence.

[0063] It should be noted that by providing a bias unit in the signal amplification module, short circuit of the induction coil can be avoided, thereby ensuring the safety of the entire circuit. In addition, by providing a filter unit in the signal amplification module, noise in the signal can be reduced, thereby improving the accuracy of the signal.

[0064] In some embodiments, the bias unit includes: a first resistor R1, a second resistor R2, and a third resistor R3, and the filter unit includes: a fourth resistor R4, a fifth resistor R5, a first capacitor C1, a second capacitor C2, and a third capacitor C3;

[0065] The first end of the first resistor R1 is connected to the negative electrode (NVCC) of the external power supply, the second end of the first resistor R1 is respectively connected to the first end of the second resistor R2 and the positive output end of the limiting module, the second end of the second resistor R2 is respectively connected to the first end of the third resistor R3 and the negative output end of the limiting module, and the second end of the third resistor R3 is connected to the positive electrode (VDD) of the external power supply;

[0066] One end R4 of the fourth resistor is connected to the second end of the first resistor R1, the other end of the fourth resistor R4, the first capacitor C1, the second capacitor C2, and the fifth resistor R5 are connected in sequence, the fifth resistor R5 is connected to the negative output end of the limiting module, a grounding node is provided between the first capacitor C1 and the second capacitor C2, a first connection point is provided between the fourth resistor R4 and the first capacitor C1, a second connection point is provided between the fifth resistor R5 and the second capacitor C2, a first end of the third capacitor C3 is connected to the first connection point, and a second end of the third capacitor C3 is connected to the second connection point; a first end of the third capacitor C3 is connected to the negative input end of the signal amplification unit, and a second end of the third capacitor is connected to the positive input end of the signal amplification unit.

[0067] It should be noted that the grounding node is used for grounding. Through the above arrangement, signal filtering is achieved while ensuring safe conduction of the circuit.

[0068] In some embodiments, the signal amplification unit includes: a sixth resistor R6 and an instrumentation amplifier U1;

[0069] One end of the third capacitor C3 is connected to the positive input terminal of the instrument amplifier U1 (such as Figure 4 The other end of the third capacitor C3 is connected to the negative input terminal of the instrument amplifier U1 (such as Figure 4 The instrument amplifier U1 is externally connected to the sixth resistor R6, and the resistance of the sixth resistor R6 is inversely proportional to the gain of the instrument amplifier U1.

[0070] like Figure 4 As shown, the instrumentation amplifier U1 is connected to the sixth resistor R6 through a preset resistor port (RG). Figure 4The "V+" port in the instrument amplifier U1 indicates the positive power port, "V-" indicates the negative power port, "VOUT" indicates the output port, and "REF" indicates the ground port. "SIG_Vo" indicates the voltage signal output by the instrument amplifier U1.

[0071] It should be noted that the gain of the instrument amplifier U1 can be adjusted by adjusting the resistance of the sixth resistor R6 .

[0072] Figure 5 For a structural diagram of an induction pulse elimination module in a pulse signal processing circuit provided in an embodiment of the present invention, please refer to Figure 5 In some embodiments, the induction pulse elimination module further includes a noise reduction unit and a bias resistor R', and the noise reduction unit includes a seventh resistor R7 and a fourth capacitor C4.

[0073] One end of the seventh resistor R7 is connected to the output end of the controller, the other end of the seventh resistor R7 is connected to the signal input end of the circuit board where the analog switch is located, the end of the seventh resistor R7 away from the controller is connected to the fourth capacitor C4, and the end of the fourth capacitor C4 away from the seventh resistor R7 is grounded.

[0074] One end of the bias resistor R' is connected to the output end of the analog switch, and the other end of the bias resistor R' is grounded.

[0075] It should be noted that by setting the noise reduction unit, the noise of the signal output by the controller can be eliminated to achieve precise control. By setting the bias resistor R', the normal conduction of the circuit can be ensured.

[0076] Figure 5 The switch in the figure is the analog switch, and the box outside the switch is the circuit board where it is located. The "COM / D" port in the circuit board is the port used to connect to the signal amplification module, "NO / S" is the output port, and the "IN" port is the signal input port, which is used to receive the control signal of the controller to realize the opening or closing control of the analog switch. "GND" is the grounding port, "V+" port indicates the positive power port, and "V-" indicates the negative power port. "SIG_FIN" is the signal passing through the analog switch. Figure 5 The SPST in represents the control signal.

[0077] Figure 6 For a schematic diagram of the structure of a filter module in a pulse signal processing circuit provided in an embodiment of the present invention, please refer to Figure 6 In some embodiments, the filtering module includes: an operational amplifier, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a fifth capacitor C5, and a sixth capacitor C6;

[0078] One end of the eighth resistor R8 is the input end of the filtering module, the other end of the eighth resistor R8, the ninth resistor R9, and the non-inverting input end of the operational amplifier are connected in sequence, one end of the fifth capacitor C5 is connected to the non-inverting input end of the operational amplifier, the other end of the fifth capacitor C5 is grounded, one end of the tenth resistor R10 is connected to the inverting input end of the operational amplifier, the other end of the tenth resistor R10 is grounded, one end of the eleventh resistor R11 is connected to the inverting input end of the operational amplifier, the other end of the eleventh resistor R11 is connected to the output end of the operational amplifier, one end of the sixth capacitor C6 is connected to one end of the eighth resistor R8 close to the ninth resistor R9, the other end of the sixth capacitor C6 is connected to the output end of the operational amplifier, and the output end of the operational amplifier is the output end of the filtering module.

[0079] It should be noted that, by setting the above circuit structure, the noise and burrs in the signal can be reduced to a good extent, and the signal-to-noise ratio of the useful signal can be improved, thereby improving the signal processing accuracy of the subsequent time-to-digital converter. Figure 6 The "SIG_FOUT" in the figure refers to the signal output by the filter module.

[0080] In order to verify the signal processing effect of the pulse signal processing circuit in the above embodiment, after many tests, it was determined that when the above pulse signal processing circuit is used to process the signal output by the induction coil, the induction pulse signal and most other noises can be eliminated, thereby improving the signal processing accuracy of the time-to-digital converter.

[0081] This embodiment also provides a magnetostrictive liquid level meter, characterized by comprising: a pulse signal processing circuit as described in any one of the above items. It should be noted that the magnetostrictive liquid level meter in this embodiment can achieve the technical effect achieved by any of the above embodiments, which will not be repeated here.

[0082] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A pulse signal processing circuit, characterized in that: Applied to magnetostrictive level gauges, including: A limiting module, which is used to perform limiting processing on a first voltage signal and a second voltage signal transmitted by an induction coil of a magnetostrictive sensor, wherein the first voltage signal refers to a voltage signal obtained according to an induction pulse signal, and the second voltage signal refers to a voltage signal obtained according to a strain pulse signal; and The signal amplification module is connected to the output of the limiting module and amplifies the output and then outputs it to the time digital converter of the magnetostrictive sensor.

2. The pulse signal processing circuit according to claim 1, characterized in that: The pulse signal processing circuit further includes: an induction pulse elimination module, the induction pulse elimination module includes: a controller and an analog switch; The controller is used to disconnect the analog switch and start timing when it is determined that the magnetostrictive sensor sends a driving pulse signal. If the accumulated timing reaches a preset time threshold, the analog switch is controlled to be turned on to eliminate the induction pulse signal. The controller is respectively connected to the signal input end of the circuit board where the magnetostrictive sensor and the analog switch are located, one end of the analog switch is connected to the output end of the signal amplification module, and the other end of the analog switch is connected to the time-to-digital converter.

3. The pulse signal processing circuit according to claim 2, characterized in that: The pulse signal processing circuit further includes: a filtering module, configured to filter the signal output by the analog switch; The input end of the filter module is connected to the output end of the analog switch, and the output end of the filter module is connected to the time-to-digital converter.

4. The pulse signal processing circuit according to claim 1, characterized in that: The limiting module includes: a first diode and a second diode; The anode of the first diode is connected to the negative output end of the induction coil, the cathode of the first diode is connected to the positive output end of the induction coil, the anode of the second diode is connected to the positive output end of the induction coil, and the cathode of the second diode is connected to the negative output end of the induction coil to form a bidirectional limiter, the cathode of the first diode is the negative output end of the limiter module, and the cathode of the second diode is the positive output end of the limiter module.

5. The pulse signal processing circuit according to claim 1 or 4, characterized in that: The signal amplification module comprises: a bias unit, a filtering unit, and a signal amplification unit which are connected in sequence.

6. The pulse signal processing circuit according to claim 5, characterized in that: The bias unit includes: a first resistor, a second resistor, and a third resistor; the filter unit includes: a fourth resistor, a fifth resistor, a first capacitor, a second capacitor, and a third capacitor; The first end of the first resistor is connected to the negative electrode of the external power supply, the second end of the first resistor is respectively connected to the first end of the second resistor and the positive output end of the limiting module, the second end of the second resistor is respectively connected to the first end of the third resistor and the negative output end of the limiting module, and the second end of the third resistor is connected to the positive electrode of the external power supply; One end of the fourth resistor is connected to the second end of the first resistor, the other end of the fourth resistor, the first capacitor, the second capacitor, and the fifth resistor are connected in sequence, the fifth resistor is connected to the negative output end of the limiting module, there is a grounding node between the first capacitor and the second capacitor, there is a first connection point between the fourth resistor and the first capacitor, there is a second connection point between the fifth resistor and the second capacitor, the first end of the third capacitor is connected to the first connection point, and the second end of the third capacitor is connected to the second connection point; the first end of the third capacitor is connected to the negative input end of the signal amplification unit, and the second end of the third capacitor is connected to the positive input end of the signal amplification unit.

7. The pulse signal processing circuit according to claim 6, characterized in that: The signal amplification unit comprises: a sixth resistor and an instrument amplifier; One end of the third capacitor is connected to the positive input terminal of the instrument amplifier, and the other end of the third capacitor is connected to the negative input terminal of the instrument amplifier. The instrument amplifier is externally connected to the sixth resistor, and the resistance of the sixth resistor is inversely proportional to the gain of the instrument amplifier.

8. The pulse signal processing circuit according to claim 2, characterized in that: The induction pulse elimination module further includes a noise reduction unit and a bias resistor, wherein the noise reduction unit includes a seventh resistor and a fourth capacitor; One end of the seventh resistor is connected to the output end of the controller, the other end of the seventh resistor is connected to the signal input end of the circuit board where the analog switch is located, one end of the seventh resistor away from the controller is connected to the fourth capacitor, and one end of the fourth capacitor away from the seventh resistor is grounded; One end of the bias resistor is connected to the output end of the analog switch, and the other end of the bias resistor is grounded.

9. The pulse signal processing circuit according to claim 3, characterized in that: The filtering module includes: an operational amplifier, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a fifth capacitor, and a sixth capacitor; One end of the eighth resistor is the input end of the filtering module, the other end of the eighth resistor, the ninth resistor, and the non-inverting input end of the operational amplifier are connected in sequence, one end of the fifth capacitor is connected to the non-inverting input end of the operational amplifier, the other end of the fifth capacitor is grounded, one end of the tenth resistor is connected to the inverting input end of the operational amplifier, the other end of the tenth resistor is grounded, one end of the eleventh resistor is connected to the inverting input end of the operational amplifier, the other end of the eleventh resistor is connected to the output end of the operational amplifier, one end of the sixth capacitor is connected to one end of the eighth resistor close to the ninth resistor, the other end of the sixth capacitor is connected to the output end of the operational amplifier, and the output end of the operational amplifier is the output end of the filtering module.

10. A magnetostrictive liquid level gauge, characterized in that: include: A pulse signal processing circuit as claimed in any one of claims 1 to 9.

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