CN1243240A - Displacement sensor - Google Patents

Abstract

A displacement sensor comprises: a magnetic core made of magnetic material linked with components, a bobbin surrounding the magnetic core, first and second coils wound on the bobbin, and The signal processing unit for detecting the position change of the magnetic core by the induced voltage on the second coil. The sensor can detect the position change of a part without using a resistor, thereby avoiding unnecessary power loss, and can make the position change detection signal have a linear characteristic without relying on an external separate signal processing device, thereby Changes in the position of components can be detected with high accuracy.

Description

Motion detector

The invention relates to a displacement sensor, in particular to a displacement sensor suitable for detecting the position of a component.

FIG. 1 is a schematic structural diagram of a displacement sensor in the prior art, wherein two coils 2 and 3 are wound on a bobbin 1 of the displacement sensor, and a magnetic core 4 made of magnetic material is linked with components in the bobbin 1 .

FIG. 2 is a circuit diagram of a displacement sensor in the prior art, wherein the resistors R1 and R2 have the same resistance, and an AC power supply AC is applied from the outside to change the inductances Z1 and Z2 of the coils on the magnetic cores 2 and 3 .

That is to say, when the position of the magnetic core 4 changes due to the driving of the components, an output voltage (e ₀ ) proportional to the position change of the magnetic core 4 will be generated; if the magnetic core 4 is placed at the center of the bobbin 1 , since the inductances Z1 and Z2 of the two coils 2 and 3 are the same, making the output voltage (e ₀ ) zero (“0”), the component displacement can be detected.

However, the displacement sensor in the prior art has the following problems: since two resistors with equal resistance must be used, when the impedance of the load terminal is low, a resistor with a low resistance must be used, which easily causes zero point drift. Therefore, high-value precision resistors are required.

In addition, there is another problem. In order to improve the accuracy of the displacement sensor, a higher voltage AC power supply is used, so that the heat loss on the resistor is high, resulting in unnecessary power consumption.

The object of the present invention is to solve the above-mentioned problems. One of its objects is to provide a displacement sensor that does not rely on resistors so as to avoid unnecessary power loss and is suitable for detecting component displacements.

Another object of the present invention is to provide a displacement sensor that can make the detected displacement have a linear characteristic and does not depend on an external signal processing device, so that the displacement of a component can be detected with high precision.

According to the above-mentioned purpose of the present invention, a kind of displacement sensor for detecting component position is provided here, and this sensor comprises:

a magnetic core made of magnetic material and linked to the component;

A bobbin that surrounds the magnetic core on the outside;

a first coil and a second coil wound on a bobbin; and

A signal processing unit for detecting changes in the position of the magnetic core according to the induced voltages of the first and second coils, the signal processing unit includes:

a first full-wave rectifier for full-wave rectifying the induced voltage of the first coil;

a second full-wave rectifier for full-wave rectification of the second coil-induced voltage;

a differential amplifier for amplifying the voltage difference after full-wave rectification by the first and second full-wave rectifiers; and

A filtering unit for filtering high frequency components in the output signal of the differential amplifier.

In order to more fully understand the objects and features of the present invention, the following detailed description of the present invention should be read with reference to the accompanying drawings, wherein:

Fig. 1 is the principle structural diagram of prior art displacement sensor;

Fig. 2 is the circuit diagram of prior art displacement sensor;

Fig. 3 is the schematic structural diagram of the displacement sensor of the present invention;

Fig. 4 is the circuit diagram of displacement sensor of the present invention;

Fig. 5 is a circuit diagram of the full-wave rectifier in Fig. 4;

Fig. 6 is the circuit diagram of differential amplifier in Fig. 4;

Fig. 7 is the circuit diagram of filtering unit and peak detection unit in Fig. 4;

Fig. 8 is a graph illustrating displacement detection results of the displacement sensor according to the present invention.

Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

Fig. 3 is the schematic structural diagram of the displacement sensor of the present invention, and Fig. 4 is the circuit diagram of the displacement sensor of the present invention, wherein the displacement sensor comprises: the magnetic core 10 that is made by magnetic material and links with parts, surrounds the magnetic core 10 outside The bobbin 11, the first coil 12 and the second coil 13 symmetrically wound on the upper and lower ends of the bobbin 11, and the signal processing for detecting the position change of the magnetic core 10 according to the induced voltage on the first and second coils 12 and 13 Unit 20.

The signal processing unit 20 includes: a first full-wave rectifier 21 for full-wave rectification of the induced voltage on the first coil 12, a second full-wave rectifier 22 for full-wave rectification of the induced voltage on the second coil 13 , a differential amplifier 23 for amplifying the voltage difference after full-wave rectification of the first and second full-wave rectifiers 21 and 22, a filter unit 24 for filtering high-frequency components in the output signal of the differential amplifier 23, and a filter unit 24 for detecting The output of the filter unit 24 is sent to the peak detection unit 25 of the maximum value and minimum value of the signal of the microcomputer 30 .

As shown in Figure 5, the first and second full-wave rectifiers 21 and 22 are made up of a plurality of resistors R1-R7, diodes D1 and D2, capacitor C1 and operational amplifiers (OP) U1 and U2; as shown in Figure 6, The differential amplifier includes a plurality of resistors R8-R11 and an operational amplifier U1.

In addition, as shown in FIG. 7 , the filter unit 24 is composed of a plurality of resistors R12 - R14 , a capacitor C2 and an operational amplifier U3; the peak detection unit 25 includes diodes D3 and D4 and capacitors C3 and C4.

The operation of the displacement sensor thus structured according to the present invention will now be described in detail.

When the frequency is 2 kilohertz (KHz) external alternating current power source AC supplies power to the first and second coils 12 and 13 and the position of the magnetic core 10 changes due to component position changes, the first and second coils 12 and 13 13 will generate an induced voltage proportional to the position change of the magnetic core 10, and the first and second full-wave rectifiers 21 and 22 perform full-wave rectification and rectify the voltage induced on the first and second coils 12 and 13 respectively. The result is output to the differential amplifier 23 .

In addition, the differential amplifier 23 amplifies the voltage difference full-wave rectified by the first and second full-wave rectifiers 21 and 22 and outputs the result to the filter unit 24 .

According to the position change of the magnetic core 10, the magnitude of the signal output by the differential amplifier 23 changes accordingly. When the magnetic core 10 is in the center of the bobbin 11, the output is "0" V; when the magnetic core 10 is in the middle of the bobbin 11 The output is "+" V when it is in the upper part, and the output is "-" V when the magnetic core 10 is located in the lower part of the bobbin 11 .

The filter unit 24 filters out the high frequency components in the output signal of the differential amplifier 23 and outputs the result to the peak detection unit 25 .

That is, in order for the microcomputer 30 to detect the position change of the component from the output signal of the differential amplifier 23, the high-frequency component in the output signal of the differential amplifier 23 should be removed.

As a result, the output of the filter unit 24 is a voltage signal proportional to the position of the component, and the voltage signal output by the filter unit 24 has a linear characteristic in a wide range, as shown in FIG. 8 .

Furthermore, in many applications the highest and lowest positions of components need to be checked more than intermediate positions, so only expected values need to be checked. The peak detection unit 25 detects the maximum and minimum values of the output signal of the filtering unit 24 and inputs them to the microcomputer 30, so that the above-mentioned requirements can be satisfied.

In other words, the peak detector 25 maintains its maximum and minimum values even if the actual position of the part changes, so that the microcomputer 30 can read and utilize the maximum and minimum values at expected times.

From the above, it is obvious that the displacement sensor of the present invention has the advantage that the position change of the component can be detected without using a resistor, thereby avoiding unnecessary power loss. Another advantage is that the detected position change signal can be given a linear characteristic without relying on the use of externally separate signal processing means, so that the position change of the component can be detected with a high degree of accuracy.

Claims (3)

1. A displacement sensor for detecting parts position, characterized in that the sensor package include: a magnetic core made of magnetic material and linked to the component; a bobbin externally surrounding said magnetic core; first and second coils wound on said bobbin; and a signal processing unit for detecting changes in the position of the magnetic core based on the voltage induced on the first and second coils. 2. The sensor according to claim 1, wherein the signal processing unit comprises: a first full-wave rectifier for full-wave rectifying the induced voltage of the first coil; a second full-wave rectifier for full-wave rectifying the induced voltage of the second coil; a differential amplifier for amplifying the full-wave rectified voltage difference between the first and second full-wave rectifiers; and A filtering unit for filtering high frequency components in the output signal of the differential amplifier. 3. The sensor according to claim 2, wherein the signal processing unit further comprises a peak detection unit for detecting the maximum and minimum values of the output signal of the filtering unit.

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