CN105277109A - Displacement sensor outputting digital frequencies - Google Patents

Abstract

The invention discloses a displacement sensor outputting digital frequencies. The displacement sensor comprises a detecting coil, a quartz crystal resonator and an oscillator. The detecting coil, the quartz crystal resonator and the oscillator form a serial loop, wherein the output frequency of the displacement sensor outputting the digital frequencies is determined by a relative displacement between the detecting coil and a detected object. The sensor is good in stability, simple in structure, high in sensitivity and capable of realizing digital frequency output.

Description

A Displacement Sensor with Digital Frequency Output

technical field

The invention belongs to the technical field of displacement sensors, and in particular relates to the design of a displacement sensor with digital frequency output.

Background technique

Displacement sensors are widely used in various fields, mainly including resistance strain gauge type, grating type, capacitive type, inductive type, etc. The measurement range of the resistance strain gauge displacement sensor is 0.1-100 μm, which is only suitable for accurate measurement in a small range; the grating type displacement sensor has a large test range and high resolution, but the equipment is complex and difficult to carry, and the optical signal is not easy to store and process; The displacement sensor has low cost and low power consumption, but its anti-interference ability is poor and it is easily affected by the environment. Moreover, most of these forms of sensor output are analog and cannot be directly connected to digital systems. Therefore, it is becoming more and more important to develop displacement sensors that can directly output digital signals.

For example, patent CN104776791A proposes a displacement sensor capable of outputting digital frequency signals, the displacement sensor includes a displacement body, an LC resonant circuit and a resonance detection module. Wherein, the displacement body of the displacement sensor passes through the inductance coil of the LC resonant circuit, and the inductance coil of the LC resonant circuit moves along the central axis of the displacement body, causing the inductance of the inductance coil of the LC resonant circuit to occur Change, so that the frequency of the LC resonant circuit changes accordingly. The displacement sensor has the advantages of digital frequency output and simple structure. However, the quality factor of the LC resonant circuit can only reach hundreds of orders of magnitude, and the stability of the signal is not ideal.

Therefore, it is of great significance to develop a displacement sensor with simple structure, good stability, digital output, high sensitivity and large detection displacement.

Contents of the invention

The purpose of the present invention is to solve the problem that most of the displacement sensors in the prior art are analog and cannot be directly connected to the digital system, and propose a displacement sensor with digital frequency output.

The technical solution of the present invention is: a displacement sensor with digital frequency output, including a detection coil, a quartz crystal resonator and an oscillator, and the detection coil, the quartz crystal resonator and the oscillator form a series loop.

Preferably, the detection coil is a PCB printed coil.

Preferably, the detection coil includes a PCB board and a printed coil fabricated on the PCB board.

Preferably, the detection coil is a solenoid type detection coil.

Preferably, the inductance of the search coil is less than 100 microhenries.

Preferably, the quartz crystal resonator is in the form of a metal package.

Preferably, the nominal frequency of the quartz crystal resonator is 5-20 MHz.

Preferably, the oscillator is a Pierce oscillator or a phase-locked loop oscillator.

The beneficial effects of the present invention are: the present invention utilizes the characteristics that the series connection formed by the detection coil and the quartz crystal resonator has a high quality factor, effectively improving the stability of the output signal of the displacement sensor; the present invention can be used in conditions such as humidity, dust, It can be used in harsh environments such as oil pollution; the invention also has a large sensing frequency traction rate and digital frequency output, and the follow-up detection circuit is simple, and the digital signal can be directly connected to the digital system, which is beneficial to the acquisition and processing of the sensing signal in the later stage; Compared with the existing sensor, it has the advantages of simple structure, convenient manufacture, and realizes the displacement measurement with the advantages of good stability, strong anti-interference ability and high sensitivity.

Description of drawings

Fig. 1 is a circuit structure diagram of a displacement sensor with digital frequency output provided by the present invention.

Fig. 2 is a side view of the detection coil of the embodiment of the present invention.

Fig. 3 is a top view of the detection coil of the embodiment of the present invention.

Fig. 4 is an equivalent circuit model diagram of the serial part of the detection coil and the quartz crystal resonator according to the embodiment of the present invention.

Description of reference signs: 1—detection coil, 2—quartz crystal resonator, 3—measured object, 4—oscillator, 11—PCB board, 12—printed coil.

detailed description

Embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

The present invention provides a displacement sensor with digital frequency output, as shown in Figure 1, comprising a detection coil 1, a quartz crystal resonator 2 and an oscillator 4, and the detection coil 1, the quartz crystal resonator 2 and the oscillator 4 form a series loop .

Wherein, the detection coil 1 adopts a PCB printed coil or a solenoid type detection coil or the like. In the embodiment of the present invention, the detection coil 1 is a PCB printed coil, as shown in FIG. 2 and FIG. 3 , including a PCB board 11 and a printed coil 12 fabricated thereon.

The inductance of the detection coil 1 is less than 100 microhenries. In the embodiment of the present invention, the inductance of the detection coil 1 is 14 microhenries.

The quartz crystal resonator 2 is packaged in metal, and its nominal frequency is 5-20MHz. In the embodiment of the present invention, the nominal frequency of the quartz crystal resonator 2 is 10 MHz.

Oscillator 4 adopts a type of oscillator such as a Pierce oscillator or a phase-locked loop oscillator.

The equivalent circuit model of the series part of the detection coil 1 and the quartz crystal resonator 2 is shown in Figure 4. According to the equivalent circuit model, the frequency sensing characteristic expression of the displacement sensor with digital frequency output can be deduced as:

$\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}\sqrt{<span\; class="notranslate">\; \&lsqb;</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; m</span>}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\sqrt{{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; m</span>}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; m</span>}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}}}<span\; class="notranslate">\; \&rsqb;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

in, L and C respectively represent the inertial mass and mechanical elasticity of the quartz crystal, C ₀ represents the static capacitance at the electrode connection of the quartz crystal resonator 2, and L _x represents the inductance of the detection coil 1. It can be known from the formula (1) that the change of the inductance L _x of the detection coil 1 will cause the output frequency f of the displacement sensor to change.

When the present invention works, as shown in FIG. 2 , the detection coil 1 is placed parallel to the measured object 3 , and the relative displacement between the measured object 3 and the detection coil 1 is adjusted in the moving direction x. The measured object 3 is a metal conductor, and in the embodiment of the present invention, the measured object 3 is a copper sheet. The output frequency of the displacement sensor with digital frequency output is determined by the relative displacement between the detection coil 1 and the measured object 3 .

Those skilled in the art will appreciate that the embodiments described here are to help readers understand the principles of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical revelations disclosed in the present invention without departing from the essence of the present invention, and these modifications and combinations are still within the protection scope of the present invention.

Claims (8)

1. a displacement transducer of digital frequency output, it is characterized in that, comprise detection coil (1), quartz crystal resonator (2) and oscillator (4), described detection coil (1), quartz crystal resonator (2 ) and the oscillator (4) form a series loop. 2. The displacement sensor with digital frequency output according to claim 1, characterized in that the detection coil (1) is a PCB printed coil. 3. The displacement sensor with digital frequency output according to claim 2, characterized in that the detection coil (1) comprises a PCB (11) and a printed coil (12) fabricated on the PCB (11). 4. The displacement sensor with digital frequency output according to claim 1, characterized in that the detection coil (1) is a solenoid type detection coil. 5. The displacement sensor with digital frequency output according to any one of claims 1-4, characterized in that the inductance of the detection coil (1) is less than 100 microhenry. 6. The displacement sensor with digital frequency output according to claim 1, characterized in that the quartz crystal resonator (2) is in the form of a metal package. 7. The displacement sensor with digital frequency output according to claim 6, characterized in that, the nominal frequency of the quartz crystal resonator (2) is 5-20 MHz. 8. The displacement sensor with digital frequency output according to claim 1, characterized in that, the oscillator (4) is a Pierce oscillator or a phase-locked loop oscillator.