CN220874515U - Signal receiving circuit and receiving equipment - Google Patents

Abstract

The utility model relates to the technical field of speed sensors, and discloses a signal receiving circuit and a receiving device. The technical solution uses an isolation circuit to perform electrical isolation between a magnetoelectric speed sensor and a receiving device, amplifies the speed signal through an amplifier circuit, and then eliminates interference through a filter circuit. The speed signal is converted into a square wave signal by a shaping circuit and then transmitted to a processor to calculate the speed. In the technical solution, the influence of the potential difference and the influence of external electromagnetic interference are reduced by an isolation circuit, and the electromagnetic interference other than the speed signal frequency is eliminated by a filter circuit. In addition, the isolation circuit in the present application connects the magnetoelectric speed sensor and the subsequent circuit. The magnetoelectric speed sensor is first electrically isolated, so there is no need to isolate the power supply of the subsequent circuit, thereby reducing the circuit structure.

Description

Signal receiving circuit and receiving device

Technical Field

The utility model relates to the technical field of rotation speed sensors, in particular to a signal receiving circuit and a receiving device.

Background technique

The magnetoelectric speed sensor uses the principle of magnetoelectric induction to measure speed, and uses the change of magnetic flux to transmit the speed information of the object being measured. When the speed measuring wheel rotates, the gap between the gear and the sensor changes periodically, and the magnetic flux also changes with the same period, so that the sensor senses a periodically changing sinusoidal signal. When the magnetoelectric speed sensor sends a sinusoidal signal to the receiving device, due to the potential difference between the magnetoelectric speed sensor and the receiving device, or a magnetoelectric speed sensor transmits signals to multiple receiving devices, there is signal interference between multiple receiving devices, or there are electromagnetic interference signals in the surrounding environment, it will cause interference in the transmission of the sinusoidal signal.

It can be seen that how to eliminate interference when the magnetoelectric speed sensor transmits signals to the receiving device is an urgent problem to be solved by those skilled in the art.

Utility Model Content

The utility model aims to provide a signal receiving circuit and a receiving device, which are used to solve the problem of interference when a magnetoelectric speed sensor transmits signals to a receiving device.

In order to solve the above technical problems, the utility model provides a signal receiving circuit, comprising:

Isolation circuit, amplifier circuit, filter circuit, shaping circuit;

The input end of the isolation circuit is connected to the magnetic induction speed sensor, and the output end is connected to the input end of the amplifier circuit, so as to electrically isolate the speed signal transmitted by the magnetic induction speed sensor and then transmit it to the amplifier circuit;

The amplifier circuit is used to amplify the connected speed signal, the output end of the amplifier circuit is connected to the input end of the filter circuit, and the output end of the filter circuit is connected to the input end of the shaping circuit to convert the signal into a square wave signal;

The output end of the shaping circuit is connected to a processor so that the processor can calculate the rotation speed according to the square wave signal.

Preferably, it also includes: a first resistor; the first resistor is connected to the output end of the isolation circuit and the input end of the amplifier circuit.

Preferably, the amplifying circuit includes: a first operational amplifier, a second operational amplifier, a third operational amplifier, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, and an eighth resistor;

The non-inverting input terminal of the first operational amplifier is connected to the first end of the first resistor as the first input terminal of the amplifier circuit, the non-inverting input terminal of the second operational amplifier is connected to the second end of the first resistor as the second input terminal of the amplifier circuit, the inverting input terminal of the first operational amplifier is connected to the first end of the second resistor and the first end of the third resistor, the inverting input terminal of the second operational amplifier is connected to the second end of the second resistor and the first end of the fourth resistor, the second end of the third resistor and the output terminal of the first operational amplifier are connected to the first end of the fifth resistor, the second end of the fourth resistor and the output terminal of the second operational amplifier are connected to the first end of the sixth resistor, the second end of the fifth resistor and the first end of the seventh resistor are connected to the non-inverting input terminal of the third operational amplifier, the second end of the seventh resistor is grounded, the second end of the sixth resistor and the first end of the eighth resistor are connected to the inverting input terminal of the third operational amplifier, and the second end of the eighth resistor and the output terminal of the third operational amplifier are connected to serve as the output terminal of the amplifier circuit.

Preferably, the filtering circuit comprises: a fourth operational amplifier, a ninth resistor, a tenth resistor, an eleventh resistor, a first capacitor, a second capacitor, and a third capacitor;

The first end of the ninth resistor is connected to the output end of the amplifier circuit as the input end of the filter circuit, the second end of the ninth resistor is connected to the first end of the tenth resistor and the first end of the first capacitor, the second end of the tenth resistor is connected to the first end of the eleventh resistor and the first end of the second capacitor, the second end of the eleventh resistor and the first end of the third capacitor are connected to the non-inverting input end of the fourth operational amplifier, the second ends of the first capacitor and the third capacitor are grounded, the inverting input end and the output end of the fourth operational amplifier and the second end of the second capacitor are connected to serve as the output end of the filter circuit.

Preferably, the shaping circuit is a hysteresis comparator circuit.

Preferably, the hysteresis comparison circuit comprises: a fifth operational amplifier, a twelfth resistor, and a thirteenth resistor;

The first end of the twelfth resistor is connected to the output end of the filtering circuit as the input end of the shaping circuit, the second end of the twelfth resistor is connected to the first end of the thirteenth resistor and the non-inverting input end of the fifth operational amplifier, the inverting input end of the fifth operational amplifier is grounded, and the output end of the fifth operational amplifier is connected to the processor as the output end of the shaping circuit.

Preferably, the second resistor is a sliding rheostat.

Preferably, the isolation circuit is an audio transformer; the primary of the audio transformer serves as the input end of the isolation circuit connected to the magnetic induction speed sensor, and the secondary serves as the output end of the isolation circuit.

In order to solve the above technical problem, the utility model also provides a receiving device, including the above signal receiving circuit.

The signal receiving circuit provided by the utility model comprises an isolation circuit, an amplifying circuit and a shaping circuit; the input end of the isolation circuit is connected to a magnetic induction speed sensor, and the output end is connected to the input end of the amplifying circuit, so as to electrically isolate the speed signal transmitted by the magnetic induction speed sensor and then transmit it to the amplifying circuit; the amplifying circuit is used to amplify the connected speed signal, the output end of the amplifying circuit is connected to the input end of the filtering circuit, and the output end of the filtering circuit is connected to the input end of the shaping circuit, so as to convert the signal into a square wave signal; the output end of the shaping circuit is connected to a processor, so that the processor can calculate the speed according to the square wave signal. Compared with the current technology, when the magnetoelectric speed sensor sends a sinusoidal signal to the receiving device, the potential difference between the magnetoelectric speed sensor and the receiving device or the electromagnetic interference signal in the surrounding environment will cause interference in the transmission of the sinusoidal signal. With this technical solution, an isolation circuit is used to electrically isolate the magnetoelectric speed sensor from the receiving device, reducing the influence of the potential difference and the influence of external electromagnetic interference. After the speed signal is amplified by the amplifier circuit, the interference signal other than the speed signal frequency is further filtered out by the filter circuit. The shaping circuit converts the speed signal as a sinusoidal signal into a square wave signal and transmits it to the processor, which calculates the speed according to the square wave signal. In this technical solution, the isolation circuit is used to eliminate the influence of the potential difference, and the filter circuit is used to filter out the interference signal other than the speed signal frequency, thereby ensuring the stability of the signal transmission. In addition, the isolation circuit in this application connects the magnetoelectric speed sensor and the subsequent circuit. The magnetoelectric speed sensor is first electrically isolated, so there is no need to isolate the power supply of the subsequent circuit, reducing the circuit structure.

In addition, the receiving device provided by the present invention includes the above-mentioned signal receiving circuit, and the effect is the same as above.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present utility model, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is a schematic diagram of the potential difference between a magnetic induction speed sensor and a signal receiver;

FIG2 is a schematic diagram of interference during signal transmission;

FIG3 is a schematic diagram of a magnetic induction speed sensor connected to multiple signal receivers;

FIG4 is a circuit diagram of a signal receiving circuit provided by an embodiment of the utility model;

The reference numerals are as follows: 1 is an isolation circuit, 2 is an amplifier circuit, 3 is a filter circuit, and 4 is a shaping circuit.

Detailed ways

The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of them. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the utility model.

Magnetic induction speed sensors are widely used as speed measurement devices. After the magnetic induction speed sensor detects the speed signal, it needs to be sent to the signal receiver for speed calculation. In the specific implementation, the signal transmission process is susceptible to interference due to the influence of the potential difference between the magnetic induction speed sensor and the signal receiver, as well as the influence of the surrounding environment. Figure 1 is a schematic diagram of the potential difference between the magnetic induction speed sensor and the signal receiver, and Figure 2 is a schematic diagram of interference during signal transmission. In addition, in the specific implementation, there is a situation where a magnetic induction speed sensor is connected to multiple signal receivers, and the speed signal needs to be transmitted to multiple signal receivers. Due to the inconsistency of the grounding methods and receiving circuits of different devices, the signal receivers affect each other, causing signal interference. Figure 3 is a schematic diagram of a magnetic induction speed sensor connected to multiple signal receivers.

The core of the utility model is to provide a signal receiving circuit and a receiving device, which are used to eliminate the interference when the magnetoelectric speed sensor transmits a signal to the receiving device.

In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

FIG4 is a circuit diagram of a signal receiving circuit provided by an embodiment of the present utility model. As shown in FIG4 , the signal receiving circuit includes:

Isolation circuit 1, amplification circuit 2, filtering circuit 3, shaping circuit 4;

The input end of the isolation circuit 1 is connected to the magnetic induction speed sensor, and the output end is connected to the input end of the amplifier circuit 2, so as to electrically isolate the speed signal transmitted by the magnetic induction speed sensor and then transmit it to the amplifier circuit 2;

The amplifier circuit 2 is used to amplify the connected speed signal, the output end of the amplifier circuit 2 is connected to the input end of the filter circuit 3, and the output end of the filter circuit 3 is connected to the input end of the shaping circuit 4 to convert the signal into a square wave signal;

The output end of the shaping circuit 4 is connected to a processor so that the processor can calculate the rotation speed according to the square wave signal.

The signal receiving circuit provided in the present application is mainly used in a receiving device, and is used to process the signal sent by the connected magnetic induction speed sensor, and then the processor calculates the speed. To avoid redundancy, the processor in this embodiment can be a processor in the receiving device, which, in addition to calculating the speed, also realizes signal processing of other circuits in the receiving device.

The isolation circuit 1 in this embodiment serves as the input end of the signal receiving circuit, connecting the magnetic induction speed sensor and the subsequent circuit. The isolation circuit 1 in this embodiment is used to achieve electrical isolation, eliminate the interference caused by the potential difference between the magnetic induction speed sensor and the receiving device, and reduce external electromagnetic interference. At the same time, electrical isolation also reduces the mutual interference between the two circuits, avoiding signal interference when one magnetic induction speed sensor is connected to multiple receiving devices.

The amplifier circuit 2 in this embodiment is used to increase the output power of the signal, and also realizes the conversion of the speed signal transmitted by the magnetic induction speed sensor into a single-ended signal.

The filter circuit 3 in this embodiment is used to filter out interference signals, mainly to filter out interference signals other than the rotation speed signal frequency, and to eliminate electromagnetic interference from the surrounding environment during the transmission process.

It is understandable that the magnetic induction speed sensor generates a sinusoidal signal when detecting the speed. In order to facilitate the processing by the subsequent processor, the sinusoidal signal needs to be converted into a square wave signal.

The signal receiving circuit provided by the utility model includes an isolation circuit, an amplifying circuit, and a shaping circuit; the input end of the isolation circuit is connected to the magnetic induction speed sensor, and the output end is connected to the input end of the amplifying circuit, so as to electrically isolate the speed signal transmitted by the magnetic induction speed sensor and then transmit it to the amplifying circuit; the amplifying circuit is used to amplify the connected speed signal and convert it into a single-ended signal, and the output end of the amplifying circuit is connected to the input end of the shaping circuit to convert the amplified signal into a square wave signal; the output end of the shaping circuit is connected to a processor, so that the processor can calculate the speed according to the square wave signal. Compared with the current technology, when the magnetoelectric speed sensor sends a sinusoidal signal to the receiving device, due to the potential difference between the magnetoelectric speed sensor and the receiving device or the electromagnetic interference signal in the surrounding environment, the interference of the sinusoidal signal transmission will be caused. With the present technical solution, the isolation circuit is used to electrically isolate the magnetoelectric speed sensor from the receiving device, and the speed signal is amplified by the amplifying circuit, and then the speed signal as a sinusoidal signal is converted into a square wave signal by the shaping circuit and then transmitted to the processor, and the processor calculates the speed according to the square wave signal. In the present technical solution, electromagnetic interference elimination is achieved through an isolation circuit, and external electromagnetic interference is reduced. The isolation circuit in the present application connects the magnetoelectric speed sensor and the subsequent circuit. The magnetoelectric speed sensor is first electrically isolated, so there is no need to isolate the power supply of the subsequent circuit, thereby reducing the circuit structure.

On the basis of the above embodiment, this embodiment further includes: a first resistor R1; the first resistor R1 is connected to the output end of the isolation circuit 1 and the input end of the amplifier circuit 2. The first resistor R1 in this embodiment is a sampling resistor, which plays the role of current limiting and voltage dividing to achieve protection of subsequent components.

This embodiment also provides a specific amplifier circuit 2, as shown in FIG4 , the amplifier circuit 2 includes: a first operational amplifier A1, a second operational amplifier A2, a third operational amplifier A3, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, and an eighth resistor R8;

The non-inverting input terminal of the first operational amplifier A1 is connected to the first end of the first resistor R1 as the first input terminal of the amplifier circuit 2, the non-inverting input terminal of the second operational amplifier A2 is connected to the second end of the first resistor R1 as the second input terminal of the amplifier circuit 2, the inverting input terminal of the first operational amplifier A1 is connected to the first end of the second resistor R2 and the first end of the third resistor R3, the inverting input terminal of the second operational amplifier A2 is connected to the second end of the second resistor R2 and the first end of the fourth resistor R4, the second end of the third resistor R3 and the output terminal of the first operational amplifier A1 are connected to the first end of the fifth resistor R5, the second end of the fourth resistor R4 and the output terminal of the second operational amplifier A2 are connected to the first end of the sixth resistor R6, the second end of the fifth resistor R5 and the first end of the seventh resistor R7 are connected to the non-inverting input terminal of the third operational amplifier A3, the second end of the seventh resistor R7 is grounded, the second end of the sixth resistor R6 and the first end of the eighth resistor R8 are connected to the inverting input terminal of the third operational amplifier A3, and the second end of the eighth resistor R8 and the output terminal of the third operational amplifier A3 are connected to serve as the output terminal of the amplifier circuit 2.

The amplifier circuit 2 provided in this embodiment is composed of three operational amplifiers. Among them, the first operational amplifier A1 and the second operational amplifier A2 are formed into a common-mode amplifier circuit 2 for the first stage amplification to achieve high impedance differential input, wherein the third resistor R3 and the fourth resistor R4 are internal feedback resistors, which realize gain adjustment with the externally configured second resistor R2. The second stage amplification uses the third operational amplifier A3 to form a differential circuit, and the fifth resistor R5, the sixth resistor R6, the seventh resistor R7, and the eighth resistor R8 are calibrated high-precision matching resistors. It can be understood that the second resistor R2 is the main component for adjusting the gain. In the specific implementation, in order to set different amplification factors of the amplifier circuit 2 according to different calculation requirements or different sensors and receiving devices, the second resistor R2 can use a sliding rheostat to adjust the resistance value according to the needs and then adjust the amplification factor.

The present embodiment also provides a specific structure of a filter circuit 3, as shown in FIG4, the filter circuit 3 includes: a fourth operational amplifier A4, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a first capacitor C1, a second capacitor C2, and a third capacitor C3;

The first end of the ninth resistor R9 is connected to the output end of the amplifier circuit 2 as the input end of the filter circuit 3, the second end of the ninth resistor R9 is connected to the first end of the tenth resistor R10 and the first end of the first capacitor C1, the second end of the tenth resistor R10 is connected to the first end of the eleventh resistor R11 and the first end of the second capacitor C2, the second end of the eleventh resistor R11 and the first end of the third capacitor C3 are connected to the non-inverting input end of the fourth operational amplifier A4, the second ends of the first capacitor C1 and the third capacitor C3 are grounded, and the inverting input end and the output end of the fourth operational amplifier A4 and the second end of the second capacitor C2 are connected together as the output end of the filter circuit 3.

The filter circuit 3 in this embodiment is a third-order low-pass filter circuit 3, which is used to filter out high-frequency interference signals other than the rotation speed signal frequency.

On the basis of the above embodiment, this embodiment further provides a specific shaping circuit 4, as shown in FIG4 , comprising: a fifth operational amplifier A5, a twelfth resistor R12, and a thirteenth resistor R13;

The first end of the twelfth resistor R12 is connected to the output end of the filter circuit 3 as the input end of the shaping circuit 4, the second end of the twelfth resistor R12 is connected to the first end of the thirteenth resistor R13 and the non-inverting input end of the fifth operational amplifier A5, the inverting input end of the fifth operational amplifier A5 is grounded, and the output end of the fifth operational amplifier A5 is connected to the processor as the output end of the shaping circuit 4.

It can be understood that the signal emitted by the magnetic induction speed sensor is a sinusoidal signal. In order to facilitate the speed calculation, the amplified speed signal needs to be converted into a waveform by the shaping circuit 4 and then transmitted to the processor for processing and calculation. The fifth operational amplifier A5, the twelfth resistor R12, and the thirteenth resistor R13 in this embodiment form a hysteresis comparison circuit to convert the sinusoidal signal into a square wave signal.

Since the principle of the magnetic induction speed sensor is similar to an induction coil, the output is an AC signal, which is different from the signals of traditional speed sensors such as proximity, opening, and Hall speed sensors. Therefore, the signal output by the magnetic induction speed sensor can be isolated by an audio transformer first, and the isolation circuit 1 is an audio transformer; the primary N1 of the audio transformer is connected to the magnetic induction speed sensor as the input end of the isolation circuit 1, and the secondary N2 is used as the output end of the isolation circuit 1.

In addition, this embodiment also provides a receiving device, which includes not only a processor but also the signal receiving circuit mentioned in the above embodiment.

The receiving device provided by the embodiment of the utility model includes a signal receiving circuit, which includes an isolation circuit, an amplifying circuit, and a shaping circuit; the input end of the isolation circuit is connected to a magnetic induction speed sensor, and the output end is connected to the input end of the amplifying circuit, so as to electrically isolate the speed signal transmitted by the magnetic induction speed sensor and then transmit it to the amplifying circuit; the amplifying circuit is used to amplify the connected speed signal, the output end of the amplifying circuit is connected to the input end of the filtering circuit, and the output end of the filtering circuit is connected to the input end of the shaping circuit to convert the signal into a square wave signal; the output end of the shaping circuit is connected to a processor, so that the processor can calculate the speed based on the square wave signal. Compared with the current technology, when the magnetoelectric speed sensor sends a sinusoidal signal to the receiving device, the interference of the sinusoidal signal transmission will be caused by the potential difference between the magnetoelectric speed sensor and the receiving device or the electromagnetic interference signal in the surrounding environment. The present technical solution uses an isolation circuit to electrically isolate the magnetoelectric speed sensor from the receiving device, eliminate the interference caused by the potential difference, and reduce external electromagnetic interference; after the speed signal is amplified by the amplifier circuit, the electromagnetic interference other than the speed signal frequency is eliminated by the filter circuit, and the shaping circuit converts the speed signal as a sinusoidal signal into a square wave signal and transmits it to the processor, and the processor calculates the speed according to the square wave signal. In the present technical solution, the interference caused by the potential difference is eliminated by the isolation circuit, and the influence of external electromagnetic interference is reduced. The electromagnetic interference other than the speed signal frequency is eliminated by the filter circuit, ensuring the stability of signal transmission. In addition, the isolation circuit in the present application connects the magnetoelectric speed sensor and the subsequent circuit. The magnetoelectric speed sensor is first electrically isolated, so there is no need to isolate the power supply of the subsequent circuit, reducing the circuit structure.

The signal receiving circuit and receiving device provided by the utility model are introduced in detail above. The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the utility model, the utility model can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the utility model.

It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

Claims (9)

1. A signal receiving circuit, comprising: Isolation circuit, amplifier circuit, filter circuit, shaping circuit; The input end of the isolation circuit is connected to the magnetic induction speed sensor, and the output end is connected to the input end of the amplifier circuit, so as to electrically isolate the speed signal transmitted by the magnetic induction speed sensor and then transmit it to the amplifier circuit; The amplifier circuit is used to amplify the connected speed signal, the output end of the amplifier circuit is connected to the input end of the filter circuit, and the output end of the filter circuit is connected to the input end of the shaping circuit to convert the signal into a square wave signal; The output end of the shaping circuit is connected to a processor so that the processor can calculate the rotation speed according to the square wave signal. 2. The signal receiving circuit according to claim 1, further comprising: a first resistor; the first resistor is connected to the output end of the isolation circuit and the input end of the amplifier circuit. 3. The signal receiving circuit according to claim 2, characterized in that the amplifying circuit comprises: a first operational amplifier, a second operational amplifier, a third operational amplifier, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, and an eighth resistor; The non-inverting input terminal of the first operational amplifier is connected to the first end of the first resistor as the first input terminal of the amplifier circuit, the non-inverting input terminal of the second operational amplifier is connected to the second end of the first resistor as the second input terminal of the amplifier circuit, the inverting input terminal of the first operational amplifier is connected to the first end of the second resistor and the first end of the third resistor, the inverting input terminal of the second operational amplifier is connected to the second end of the second resistor and the first end of the fourth resistor, the second end of the third resistor and the output terminal of the first operational amplifier are connected to the first end of the fifth resistor, the second end of the fourth resistor and the output terminal of the second operational amplifier are connected to the first end of the sixth resistor, the second end of the fifth resistor and the first end of the seventh resistor are connected to the non-inverting input terminal of the third operational amplifier, the second end of the seventh resistor is grounded, the second end of the sixth resistor and the first end of the eighth resistor are connected to the inverting input terminal of the third operational amplifier, and the second end of the eighth resistor and the output terminal of the third operational amplifier are connected to serve as the output terminal of the amplifier circuit. 4. The signal receiving circuit according to claim 3, characterized in that the filtering circuit comprises: a fourth operational amplifier, a ninth resistor, a tenth resistor, an eleventh resistor, a first capacitor, a second capacitor, and a third capacitor; The first end of the ninth resistor is connected to the output end of the amplifier circuit as the input end of the filter circuit, the second end of the ninth resistor is connected to the first end of the tenth resistor and the first end of the first capacitor, the second end of the tenth resistor is connected to the first end of the eleventh resistor and the first end of the second capacitor, the second end of the eleventh resistor and the first end of the third capacitor are connected to the non-inverting input end of the fourth operational amplifier, the second ends of the first capacitor and the third capacitor are grounded, the inverting input end and the output end of the fourth operational amplifier and the second end of the second capacitor are connected to serve as the output end of the filter circuit. 5 . The signal receiving circuit according to claim 4 , wherein the shaping circuit is a hysteresis comparator circuit. 6. The signal receiving circuit according to claim 5, characterized in that the hysteresis comparison circuit comprises: a fifth operational amplifier, a twelfth resistor, and a thirteenth resistor; The first end of the twelfth resistor is connected to the output end of the filtering circuit as the input end of the shaping circuit, the second end of the twelfth resistor is connected to the first end of the thirteenth resistor and the non-inverting input end of the fifth operational amplifier, the inverting input end of the fifth operational amplifier is grounded, and the output end of the fifth operational amplifier is connected to the processor as the output end of the shaping circuit. 7 . The signal receiving circuit according to claim 3 , wherein the second resistor is a sliding resistor. 8. The signal receiving circuit according to any one of claims 1 to 7 is characterized in that the isolation circuit is an audio transformer; the primary of the audio transformer serves as the input end of the isolation circuit connected to the magnetic induction speed sensor, and the secondary serves as the output end of the isolation circuit. 9. A receiving device, characterized by comprising the signal receiving circuit according to any one of claims 1 to 8.