Road geomagnetic signal acquisition driving circuit

Abstract

According to the road geomagnetic signal acquisition driving circuit provided by the utility model, the primary amplification circuit, the secondary amplification circuit, the primary compensation circuit and the secondary compensation circuit are arranged; the primary compensation circuit is connected with an REF port of the primary amplification circuit and is used for outputting reference voltage of the primary amplification circuit; and the secondary compensation circuit is connected with the negative input end of the secondary amplification circuit and is used for compensating the offset voltage of the geomagnetic signal acquisition driving circuit, so that the interference of an external signal on the acquired geomagnetic signal is effectively reduced, and the data detection precision is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of traffic monitoring, in particular to a highway geomagnetic signal acquisition drive circuit. Background Art

[0002] As urban road congestion becomes increasingly serious, intelligent transportation systems have become a research hotspot in the transportation field of various countries. The vehicle detection system is the most important component of the intelligent transportation system, responsible for collecting road vehicle parameters. The accuracy of the collected data directly affects the subsequent control accuracy of the entire intelligent transportation system. At present, common vehicle detection systems at home and abroad mainly use Hall sensors, anisotropic magnetoresistance sensors, giant magnetoresistance sensors, tunnel magnetoresistance sensors and other sensors as sensors for geomagnetic data collection, especially tunnel magnetoresistance sensors, which have the advantages of high temperature stability, simple circuit, low hysteresis, low power consumption, and wide operating voltage range. However, since the sensitivity of tunnel magnetoresistance sensors is much higher than that of other sensors and the output voltage is low, they are particularly susceptible to interference from external signals, resulting in reduced detection accuracy. Utility Model Content

[0003] In view of the above problems, the utility model proposes a highway geomagnetic signal acquisition driving circuit to solve the problems existing in the background technology.

[0004] The technical solution adopted by the utility model is:

[0005] A highway geomagnetic signal acquisition driving circuit, the highway geomagnetic signal acquisition driving circuit comprising a primary amplification circuit, a secondary amplification circuit, a primary compensation circuit and a secondary compensation circuit, the gain of the primary amplification circuit being greater than the gain of the secondary amplification circuit;

[0006] The input differential end of the primary amplifier circuit is connected to the output end of the geomagnetic sensor;

[0007] The positive input end of the secondary amplifier circuit is connected to the output end of the primary amplifier circuit, and the output end of the secondary amplifier circuit is connected to the digital signal processing circuit via the AD conversion circuit;

[0008] The primary compensation circuit is connected to the REF port of the primary amplifier circuit and is used to output a reference voltage of the primary amplifier circuit;

[0009] The secondary compensation circuit is connected to the negative input terminal of the secondary amplifier circuit and is used to compensate for the offset voltage of the geomagnetic signal acquisition drive circuit.

[0010] Further, the primary amplification circuit includes an AD8231 amplifier;

[0011] The secondary amplifier circuit includes an AD8221 amplifier;

[0012] The positive input terminal of the secondary amplifier circuit is connected to the output terminal of the primary amplifier circuit through a filter circuit.

[0013] Furthermore, the primary compensation circuit includes a REF2925 voltage reference chip, and the output reference voltage of the REF2925 voltage reference chip is 2.5V.

[0014] Further, the secondary compensation circuit includes a MAX6037 chip and an adjustable resistance peripheral circuit;

[0015] The output of the MAX6037 chip is connected in parallel with the adjustable resistance peripheral circuit and then connected to the negative input terminal of the secondary amplifier circuit.

[0016] Furthermore, the geomagnetic sensor adopts a three-axis tunnel magnetoresistance sensor;

[0017] The X-axis, Y-axis and Z-axis voltage output signals of the three-axis tunnel magnetoresistance sensor are respectively connected to one of the geomagnetic signal acquisition drive circuits.

[0018] Furthermore, the AD conversion circuit is a 16-bit AD converter, and the digital signal processing circuit includes an STM8S103F3 processor.

[0019] Furthermore, the power supply voltage of the geomagnetic signal acquisition drive circuit is DC positive and negative 5V.

[0020] Furthermore, the input differential end of the primary amplifier circuit is connected to the output end of the geomagnetic sensor through a shielded line.

[0021] The highway geomagnetic signal acquisition and driving circuit provided by the utility model is provided with a primary amplifying circuit, a secondary amplifying circuit, a primary compensation circuit and a secondary compensation circuit; the primary compensation circuit is connected to the REF port of the primary amplifying circuit and is used to output the reference voltage of the primary amplifying circuit; the secondary compensation circuit is connected to the negative input end of the secondary amplifying circuit and is used to compensate for the offset voltage of the geomagnetic signal acquisition and driving circuit, thereby effectively reducing the interference of external signals on the collected geomagnetic signals and improving the accuracy of data detection.

[0022] The above description is only an overview of the technical solution of the utility model. In order to more clearly understand the technical means of the utility model, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the utility model more obvious and easy to understand, the specific implementation methods of the utility model are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] By reading the detailed description of the preferred embodiment below, various other advantages and benefits will become clear to those of ordinary skill in the art. The accompanying drawings are only used for the purpose of illustrating the preferred embodiment and are not considered to be limiting of the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0024] Figure 1 The schematic diagram of the highway geomagnetic signal acquisition and driving circuit of the utility model is shown.

[0025] Figure 2 The circuit diagram of the primary amplifying circuit and the primary compensating circuit of the utility model is shown.

[0026] Figure 3 The circuit diagram of the secondary amplification circuit and the secondary compensation circuit of the utility model is shown. DETAILED DESCRIPTION

[0027] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0028] refer to Figure 1 , a highway geomagnetic signal acquisition driving circuit of this embodiment, the geomagnetic signal acquisition driving circuit includes a primary amplification circuit, a secondary amplification circuit, a primary compensation circuit and a secondary compensation circuit, and the power supply voltage of the geomagnetic signal acquisition driving circuit is DC positive and negative 5V.

[0029] Since the primary amplifier has the greatest impact on the total noise voltage, in order to reduce the impact of secondary noise on the entire circuit, the gain of the primary amplifier circuit needs to be increased, and the positive input end of the secondary amplifier circuit is connected to the output end of the primary amplifier circuit through a low-pass filter circuit. In this embodiment, the gain of the primary amplifier circuit is set to be greater than the gain of the secondary amplifier circuit. Specifically, refer to Figure 2 and 3 The primary amplifier circuit of this embodiment includes an AD8231 amplifier, and the secondary amplifier circuit includes an AD8221 amplifier and peripheral circuits; the primary compensation circuit includes a REF2925 voltage reference chip, and the output reference voltage of the REF2925 voltage reference chip is 2.5V. The secondary compensation circuit includes a MAX6037 chip and an adjustable resistor peripheral circuit, and the output of the MAX6037 chip is connected in parallel with the adjustable resistor peripheral circuit and then connected to the negative input terminal of the secondary amplifier circuit.

[0030] The input differential end of the primary amplifier circuit is connected to the output end of the geomagnetic sensor. Specifically, the geomagnetic sensor of this embodiment adopts a three-axis tunnel magnetoresistance sensor (TMR). TMR is made by the principle of tunnel magnetoresistance effect. It is composed of three one-dimensional tunnel magnetoresistance sensors orthogonally combined. It adopts 3 push-pull Wheatstone full bridge structure design. Three independent output differential voltages are determined by the output voltage of the Wheatstone full bridge on each axis. It can be widely used in weak magnetic field detection, position sensor and three-dimensional space measurement and other fields, and can meet the weak geomagnetic field signal detection needs. There is a fairly stable magnetic field within a certain range on the surface of the earth. As a large ferromagnetic object, the car can be regarded as a model of a bipolar magnet. The magnetic induction intensity around the vehicle changes regularly due to the interaction between the vehicle's own magnetic field and the geomagnetic field. When the vehicle enters the detection range, the three-axis tunnel magnetoresistance sensor will convert the geomagnetic field signal of the three components into voltage output. Specifically, the X-axis, Y-axis and Z-axis voltage output signals of the three-axis tunnel magnetoresistance sensor are respectively connected to the geomagnetic signal acquisition drive circuit.

[0031] The positive input end of the secondary amplifier circuit is connected to the output end of the primary amplifier circuit, and the output end of the secondary amplifier circuit is connected to the digital signal processing circuit via the AD conversion circuit. Specifically, the AD conversion circuit is a 16-bit AD converter. Of course, in order to improve the accuracy of data acquisition, a 32-bit AD converter can also be used. The digital signal processing circuit includes a DSP processor, such as an STM8S103F3 processor. Since the processing of geomagnetic signals does not require extremely fast speed and real-time performance, the processor can meet general data processing needs. In practical applications, the digital signal processing circuit can also be implemented using an ordinary single-chip circuit. After the digital signal processing circuit processes the signal, it can be transmitted to the highway signal control system in the background. The primary compensation circuit is connected to the REF port of the primary amplifier circuit, which is used to output the reference voltage of the primary amplifier circuit, and raise the reference voltage to 2.5V, thereby improving the anti-interference performance of the primary amplifier circuit; the secondary compensation circuit is connected to the negative input end of the secondary amplifier circuit, which is used to compensate for the offset voltage of the geomagnetic signal acquisition drive circuit, and can compensate for the interference of external noise.

[0032] To avoid interference from external signals, the input differential end of the primary amplifier circuit is connected to the output end of the geomagnetic sensor through a shielded wire, and a coaxial signal line is generally used for connection. The three-axis tunnel magnetoresistance sensor needs to be installed in an unshielded space to avoid it being unable to sense the geomagnetic signal. Generally, it is installed in a box made of aluminum alloy or polymer.

[0033] The highway geomagnetic signal acquisition and driving circuit of the above embodiment is adopted, by setting a primary amplifier circuit, a secondary amplifier circuit, a primary compensation circuit and a secondary compensation circuit; the primary compensation circuit is connected to the REF port of the primary amplifier circuit, and is used to output the reference voltage of the primary amplifier circuit; the secondary compensation circuit is connected to the negative input end of the secondary amplifier circuit, and is used to compensate for the offset voltage of the geomagnetic signal acquisition and driving circuit, thereby effectively reducing the interference of external signals on the collected geomagnetic signals and improving the accuracy of data detection.

[0034] Those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present invention and to form different embodiments.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the utility model.

Claims

1. A highway geomagnetic signal acquisition drive circuit, characterized in that: The highway geomagnetic signal acquisition driving circuit comprises a primary amplifying circuit, a secondary amplifying circuit, a primary compensation circuit and a secondary compensation circuit, and the gain of the primary amplifying circuit is greater than the gain of the secondary amplifying circuit; The input differential end of the primary amplifier circuit is connected to the output end of the geomagnetic sensor; The positive input end of the secondary amplifier circuit is connected to the output end of the primary amplifier circuit, and the output end of the secondary amplifier circuit is connected to the digital signal processing circuit via the AD conversion circuit; The primary compensation circuit is connected to the REF port of the primary amplifier circuit and is used to output a reference voltage of the primary amplifier circuit; The secondary compensation circuit is connected to the negative input terminal of the secondary amplifier circuit and is used to compensate for the offset voltage of the geomagnetic signal acquisition drive circuit.

2. A highway geomagnetic signal acquisition driving circuit according to claim 1, characterized in that: The primary amplification circuit includes an AD8231 amplifier; The secondary amplifier circuit includes an AD8221 amplifier; The positive input terminal of the secondary amplifier circuit is connected to the output terminal of the primary amplifier circuit through a filter circuit.

3. A highway geomagnetic signal acquisition driving circuit according to claim 1, characterized in that: The primary compensation circuit includes a REF2925 voltage reference chip, and the output reference voltage of the REF2925 voltage reference chip is 2.5V.

4. A highway geomagnetic signal acquisition and driving circuit according to claim 1, characterized in that: The secondary compensation circuit includes a MAX6037 chip and an adjustable resistance peripheral circuit; The output of the MAX6037 chip is connected in parallel with the adjustable resistance peripheral circuit and then connected to the negative input terminal of the secondary amplifier circuit.

5. A highway geomagnetic signal acquisition and driving circuit according to claim 1, characterized in that: The geomagnetic sensor adopts a three-axis tunnel magnetoresistance sensor; The X-axis, Y-axis and Z-axis voltage output signals of the three-axis tunnel magnetoresistance sensor are respectively connected to one of the geomagnetic signal acquisition drive circuits.

6. A highway geomagnetic signal acquisition driving circuit according to claim 1, characterized in that: The AD conversion circuit is a 16-bit AD converter, and the digital signal processing circuit includes an STM8S103F3 processor.

7. A highway geomagnetic signal acquisition and driving circuit according to claim 1, characterized in that: The power supply voltage of the geomagnetic signal acquisition drive circuit is DC positive and negative 5V.

8. The highway geomagnetic signal acquisition driving circuit according to claim 1, characterized in that: The input differential end of the primary amplifier circuit is connected to the output end of the geomagnetic sensor through a shielded line.

Images