CN111336908A - Novel inductance micrometer - Google Patents

Abstract

The invention belongs to the field of electronic technology and provides a novel electric micrometer. The proposed new type of electric micrometer adopts digital synthesis technology to synthesize sine wave in the sine wave generator link, provides a single frequency sine wave signal to the sensor, and adopts direct sampling and analysis of the AC signal; the CPU call is stored in the ROM inside the chip. The sine wave data is sent to the DAC port, and the DAC outputs the corresponding sine wave voltage. After band-pass filtering and amplification, a single frequency sine wave is output to the sensor input end OSC to complete the signal excitation of the sensor; the sensor output signal is amplified by the operational amplifier , and then biased by the bias circuit to obtain the DC signal containing the AC component, which is output to the ADC for sampling; the digital signal is analyzed by Fourier transform software, and the amplitude and phase of the AC signal are calculated according to the output timing of the DAC, and the displacement of the sensor is obtained. magnitude. The measurement accuracy and stability of the present invention are greatly improved.

Description

A new type of electric micrometer

technical field

The invention belongs to the technical field of electronics, and in particular relates to a novel electric micrometer.

Background technique

The electric micrometer is an instrument that uses the displacement change of the inductive sensor (LVDT) to realize the display and transmission of the displacement. It can be widely used in aerospace, machinery, construction, textile, railway, coal, metallurgy, plastics, chemical industry and scientific research institutes It is a high-tech product that can be used to measure elongation, vibration, object thickness, expansion, etc.

The inductance micrometer is a precision instrument that uses the electromagnetic induction principle of the inductive sensor to realize the change of the inductance of the sensor caused by the change of the displacement, and then detects the change through the circuit to realize the pointer display or digital display.

The structure of the inductive sensor is composed of a magnetic core, a magnetic sleeve, a primary coil and a secondary coil. The self-inductance principle can also be used to take out the middle tap for the secondary output; the primary coil and the secondary coil are distributed on the coil bobbin, and the magnetic core can be placed in the coil. Free movement inside. When the primary coil is applied with an AC voltage of a certain frequency, the magnetic core moves in the coil, which changes the magnetic field distribution in the space, thereby changing the mutual inductance between the primary and secondary coils, and the secondary coil generates different induced voltages. In this way, the displacement of the magnetic core becomes an AC voltage signal output.

The schematic diagram of the traditional electric micrometer is shown in Figure 1.

In the traditional circuit, the sine wave that excites the sensor is generated by the LC oscillator. Due to the limitation of the inductive three-point structure, the generated sine wave has poor frequency stability and unsatisfactory amplitude stability, which affects the entire measurement system. stability.

The phase-sensitive rectification link in the traditional circuit is composed of a bridge rectifier circuit composed of four diodes. Due to the nonlinearity of the diodes and sensitivity to temperature, the linearity and temperature stability of the entire system are determined to be insufficient.

SUMMARY OF THE INVENTION

The purpose of the present invention is to propose a new type of electric micrometer, which can improve the precision and stability of the electric micrometer.

The present invention adopts following technical scheme for accomplishing above-mentioned purpose:

A new type of electric micrometer, which uses digital synthesis technology to synthesize sine waves in the sine wave generator, provides a single frequency sine wave signal to the sensor, and improves the frequency and amplitude stability; in order to improve the linearity and stability of the sensor , to eliminate the nonlinear and unstable factors caused by the phase-sensitive rectifier circuit, and to directly sample and analyze the AC signal to obtain the earlier complete data of the sensor; further, the CPU calls the sine wave data stored in the ROM inside the chip, It is sent to the DAC port, and the DAC outputs the corresponding sine wave voltage. After band-pass filtering and amplification, it outputs a single frequency sine wave to the sensor input end OSC to complete the signal excitation of the sensor; the AC signal output by the sensor is operationally amplified and then output to the isolation The direct capacitor is then biased by the bias circuit to provide a DC level to the AC signal, and a DC signal containing the AC component is obtained, which is output to the ADC for sampling; the obtained digital signal is analyzed by Fourier transform software, and the output is based on the DAC The time sequence is calculated by the Fourier transform software to calculate the amplitude and phase of the AC signal, and the displacement value of the sensor is obtained; further, the STM32H750 chip of STMicroelectronics is used. The STM32H750 chip has a built-in 12BIT DAC and 16BIT ADC. .

The measurement accuracy and stability of the electric micrometer obtained by adopting the technical solution of the present invention are greatly improved.

Description of drawings

Fig. 1 is the principle block diagram of the traditional electric micrometer.

FIG. 2 is a principle block diagram of the present invention.

FIG. 3 is an electrical schematic diagram of the DAC sine wave synthesis of the present invention.

Figure 4 is an electrical schematic diagram of the sensor output signal processing.

Detailed ways

The present invention is described with reference to the accompanying drawings and specific embodiments;

As shown in Figure 2, Figure 3 and Figure 4, a new type of inductance micrometer adopts ST STMicroelectronics' STM32H750 chip, which has built-in 12BIT DAC (digital-to-analog converter) and 16BIT ADC (analog-to-digital conversion). The CPU calls the sine wave data stored in the ROM inside the chip and sends it to the DAC port, and the DAC outputs the corresponding sine wave voltage; it goes through the band-pass filter circuit composed of R1, C1, R2, and C2 and is amplified by the operational amplifier N1A Then load it to the input end of the sensor, and provide the sensor with a sine wave signal of a single frequency as the excitation signal of the sensor; this signal is closely related to the frequency of the single-chip crystal oscillator, so the frequency is very accurate and stable; the output signal of the sensor is amplified by the operational amplifier N1B. Output from pin 7 to CX1 DC blocking capacitor, and get a DC signal containing AC components through the bias circuit composed of RP1 and RP2, which is directly sent to ADC for sampling; the obtained digital signal is FFT (Fourier transform software). ) to analyze, accurately calculate the amplitude and phase of the AC signal according to the DAC output timing, and get the displacement value of the sensor; send the data to the LCD display, you can see the displacement of the sensor more intuitively, and through the RS232 communication port, you can send the data to the output to an external device.

Claims (1)

1. The utility model provides a novel inductance micrometer, its characterized in that: synthesizing sine waves by adopting a digital synthesis technology in a sine wave generator link, and providing sine wave signals with single frequency for a sensor; sampling and analyzing the alternating current signal directly so as to obtain earlier complete data of the sensor; further, the CPU calls sine wave data stored in a ROM in the chip and sends the sine wave data to a DAC port, the DAC outputs corresponding sine wave voltage, single-frequency sine waves are output to a sensor input end OSC after band-pass filtering and amplification, and signal excitation of the sensor is completed; the AC signal output by the sensor is output to a DC blocking capacitor after operational amplification, and then is biased by a bias circuit to provide a DC level for the AC signal so as to obtain a DC signal containing an AC component, and the DC signal is output to an ADC (analog to digital converter) for sampling; analyzing the obtained digital signal by adopting Fourier transform software, and calculating the amplitude and the phase of the alternating current signal by the Fourier transform software according to the DAC output time sequence to obtain the displacement value of the sensor; furthermore, an STM32H750 chip of ST semiconductor company is adopted, and a 12-BIT DAC and a 16-BIT ADC are arranged in the STM32H750 chip.

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