CN217877730U

CN217877730U - LC sensor time domain readout system

Info

Publication number: CN217877730U
Application number: CN202222346290.8U
Authority: CN
Inventors: 丁镓骏; 缪谨柒; 张文斌; 耿圆; 赵子瑞; 徐欣筑; 张彬辉; 黄俊晟; 赵辉东; 王世杰; 姚飞
Original assignee: China Jiliang University
Current assignee: China Jiliang University
Priority date: 2022-09-05
Filing date: 2022-09-05
Publication date: 2022-11-22
Anticipated expiration: 2032-09-05

Abstract

The utility model discloses a LC sensor time domain readout system, this time domain readout system comprises reading out circuit, time-frequency domain conversion unit, display element triplex. The reading circuit converts a received sensor signal into a time-domain readable voltage signal which is time-domain oscillation attenuation, the time-frequency domain conversion unit is used for collecting and processing the signal by matching a field programmable gate array with a high-speed ADC module, so that the conversion between a time domain and a frequency domain is realized, the frequency corresponding to the maximum value of the equivalent impedance imaginary part of the reading system is calculated, namely the resonance frequency of the LC passive wireless sensor, and finally the real-time display of the impedance imaginary part waveform and the resonance frequency is carried out through the display unit. The time domain readout system can realize the real-time, quick and low-power-consumption accurate measurement of the resonance frequency of the LC sensor, is insensitive to the coupling coefficient, is not limited by the coupling distance, and can realize the real-time monitoring of sensitive environmental parameters.

Description

LC sensor time domain readout system

Technical Field

The utility model belongs to the technical field of the pressure sensing technique and specifically relates to a LC sensor time domain readout system.

Background

The LC passive wireless sensor has the characteristics of small volume, low power consumption, long service life, strong adaptability and the like, can perform inductive coupling wireless reading through a resonance loop formed by an inductor and a capacitor, has very simple structural design, and can be applied to various severe environments such as high temperature, high pressure, tightness, rotation and the like. At present, most researches on LC passive wireless sensors focus on the research on the sensors, and the reading mode of the resonant frequency is single.

At present, a network analyzer and an impedance analyzer are mostly adopted to measure in a frequency domain mode. However, the large-scale integrated equipment is only suitable for fixed parameter measurement, and cannot achieve the miniaturization and integration characteristics required at present, and the disadvantage brought by the frequency sweeping mode is that the requirement on the measurement time is too long, and the measurement of sensitive parameters which change rapidly cannot be met.

The time domain readout method is high in measurement speed and short in period, can realize rapid measurement of the resonant frequency of the LC passive wireless sensor, and can meet the development requirements of the times, but the time domain readout method is high in acquisition difficulty of effective signals, complex in processing circuit and high in implementation difficulty.

Therefore, a new reading method and a new reading principle are urgently needed to be provided, the research field and the research process of the LC passive wireless sensor are further expanded, a time domain reading system capable of quickly measuring the resonance frequency change of the multi-parameter LC sensor is constructed, and the defect that the resonance frequency reading mode of the LC passive wireless sensor is single is overcome.

SUMMERY OF THE UTILITY MODEL

The utility model discloses constitute by reading circuit, time-frequency domain conversion unit, display element. The readout circuit is connected with the time-frequency domain conversion unit, and the time-frequency domain conversion unit is connected with the display unit. The readout circuit is composed of a movable voltage source and a switching circuit module. The switching circuit is composed of a switch, a first capacitor, a second capacitor, a first resistor, a second resistor, a third resistor and a reading coil. The switch, the first capacitor, the second capacitor, the first resistor, the second resistor and the readout coil are connected in series, and the second capacitor and the third resistor are connected in parallel and grounded. The time-frequency domain conversion unit consists of a field programmable logic gate array and a high-speed ADC module.

In order to increase the measurement speed of the readout circuit, it is preferable to use a voltage-controlled analog switch MAX4644 as a switch of the circuit. The MAX4644 switch is a single-pole double-throw low-power switch and can be switched between two loops quickly. Charging the second capacitor when switched into a loop connected to a movable voltage source; the second capacitor starts to discharge when switched into a loop in series with the first capacitor. The switch has small on-resistance of only 4 omega, on-time of 11ns-15ns and off-time of 3ns-5ns, and provides a path to the ground for the discharge of the second capacitor when the switch is arranged at b through the rapid switching among different loops and ensuring that the path is approximately broken when the switch is arranged at a, so that the whole circuit can be ensured to transmit signals stably to the maximum extent while maintaining transient characteristics, and the requirement of the reading circuit on high-speed measurement can be greatly met.

In order to meet the requirement of the stability of the reading circuit, preferably, the planar inductor printed on the PCB is used for experimental measurement, and the planar inductor drawn on the PCB has stronger stability and is convenient for integration with other electronic components.

Preferably, the inductance value of the readout coil is in the range of 2.16-10.24 μ H.

In order to realize the integration and operability of the time-frequency domain conversion unit, it is preferable that a field programmable gate array is adopted to cooperate with a high-speed ADC chip to collect and process signals, and a fast fourier transform algorithm in the prior art is used to realize the time-frequency domain conversion of the signals.

In order to meet the data acquisition scheme with high speed and low power consumption required by the system, preferably, an integrated DAQ4225 high-speed ADC module and a low-power-consumption high-performance analog-to-digital conversion chip thereof are adopted, so that dual-channel 12-bit high-speed 125MSPS analog-to-digital conversion can be realized, and the total power is only 277mW.

In order to facilitate reading of the conversion result, preferably, the HDMI external display screen is adopted, so that the change condition of the equivalent impedance imaginary part of the system can be displayed more objectively, and the real-time dynamic display of the resonant frequency of the system and the maximum value of the impedance imaginary part can be realized.

The system operates by converting the received sensor signal into a time-domain readable voltage signal attenuated by a time-domain oscillation by the readout circuit. The voltage signal is collected in the time-frequency domain conversion unit and converted into the expression forms of frequency and impedance in the frequency domain, the calculation of the resonance frequency of the system is realized by judging the most value of the imaginary part of the impedance, and the visualization of the result is realized by utilizing the display unit.

Compare in current research, this utility model's optimization innovation lies in, the system can realize reading LC sensor system resonant frequency's in succession fast, and single measurement's total time consuming is short, and measured power is little. Under the control of the field programmable gate array, the repeated rapid measurement of the resonance frequency of the LC sensor can be realized, and a stable and effective method is provided for rapidly reading the environment sensitive signals of a real-time monitoring system.

Drawings

The invention is further described with reference to the following figures and examples.

FIG. 1 is a block diagram of the overall principle design of the present invention;

fig. 2 is a schematic diagram of a readout circuit according to the present invention;

fig. 3 shows a read coil in the read circuit of the present invention.

Detailed Description

To further illustrate the technical solutions adopted by the present invention to achieve the predetermined purpose of the present invention, the following detailed description is made with reference to the accompanying drawings and preferred embodiments as follows:

fig. 1 is a block diagram of the system of the present invention, which is composed of a readout circuit 1, a time-frequency domain conversion unit 2 and a display unit 3. The readout circuit 1 is connected to the time-frequency domain conversion unit 2, and the time-frequency domain conversion unit 2 is connected to the display unit 3. According to the change of the environmental parameter to be measured, the parameter of the sensitive element of the LC passive wireless sensor changes, and the received sensor signal is transmitted to the readout circuit 1. The readout circuit 1 consists of a movable voltage source 11 and a switching circuit module 12. The time-frequency domain conversion unit 2 is composed of a field programmable gate array 21 and a high-speed ADC module 22.

Fig. 2 is a schematic diagram of the readout circuit of the present invention, and the switching circuit module 12 is composed of a switch 121, a first capacitor 122, a second capacitor 123, a first resistor 124, a second resistor 125, a third resistor 126, and a readout coil 127. In the switching circuit module 12, the switch 121, the first capacitor 122, the second capacitor 123, the first resistor 124, the second resistor 125, and the readout coil 127 form a series circuit, and both ends of the second capacitor 123 are connected in parallel to the third resistor 126 and grounded.

Fig. 3 shows a shape of the readout coil 127, and experimental measurements are performed by using a planar inductor printed on a PCB, so that the planar inductor drawn on the PCB has higher stability and is convenient for integration with other electronic components.

The overall readout circuit 1 operates as follows: in an initial state, the switch 121 is placed at the end a, and the movable voltage source 12 charges the second capacitor 123 until the voltage across the second capacitor 123 is equal to the movable voltage source; the switch 121 is placed at the end b, and the second capacitor 123 starts to discharge, so as to obtain a cluster of damped oscillation signals. When the charge injection effect occurs, the coupled charges are stored in the first capacitor 122, and when the switch 121 is placed at a, the third resistor 126 provides a path to the ground for the first capacitor 122 to discharge the internally stored charges, so as to reduce the influence of the charge injection effect on the circuit, thereby realizing the purpose of converting the sensor signal into a time-domain readable voltage signal, wherein the time-domain readable voltage signal is a time-domain oscillation attenuation signal.

The sensitivity of the readout coil 127 to the oscillation signal is high, so that a signal which is easier to read can be obtained, the coupling coefficient can achieve the best effect, and time-frequency domain transformation can be conveniently carried out on the coupling coefficient.

The time-frequency domain conversion unit 2 collects the time domain oscillation signals, converts the time domain oscillation signals into the expression forms of frequency and impedance in the frequency domain, calculates the system resonance frequency by judging the most value of the imaginary part of the impedance, and then realizes the visualization of the result by using the display unit 3.

The display unit 3 adopts a mode that the HDMI is externally connected with a display screen to dynamically display the measurement result in real time, can more objectively display the change condition of the equivalent impedance imaginary part of the system, realizes real-time dynamic display of the resonance frequency and the maximum value of the impedance imaginary part of the system by drawing a sampling point-impedance imaginary part curve, and is more convenient to observe and record the change of a data result.

To sum up, the utility model provides a passive wireless sensor time domain readout system of LC. The system utilizes the switch 121 to switch and form a time domain oscillation attenuation signal with coupling information, converts a time domain voltage signal from a time domain signal to a complex frequency domain signal by applying a fast Fourier transform algorithm in the prior art, and determines the resonance frequency of the sensor through the maximum imaginary part of the equivalent impedance of the system. The method has high measurement speed, can realize the purpose of quickly measuring the resonant frequency of the sensor, and further can realize the real-time monitoring of sensitive environmental parameters. The field programmable gate array 21 is matched with the high-speed ADC module 22 to acquire and process signals, the signals are converted through a fast Fourier transform algorithm in the prior art, the frequency corresponding to the maximum value of the imaginary part of the equivalent impedance of the reading system is calculated, and the waveform and the resonant frequency are displayed through the display unit 3. Through measurement, the system can realize real-time, quick and low-power-consumption reading of the resonant frequency of the LC sensor.

While the preferred embodiments of the present invention have been described, the present invention is not limited to the above embodiments, and those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and such equivalent modifications or substitutions are intended to be included within the scope of the present invention defined by the appended claims.

Claims

1. An LC sensor time domain readout system, characterized by: the system consists of a reading circuit, a time-frequency domain conversion unit and a display unit; the reading circuit is connected with the time-frequency domain conversion unit, and the time-frequency domain conversion unit is connected with the display unit; the reading circuit consists of a movable voltage source and a switching circuit module; the switching circuit module consists of a switch, a first capacitor, a second capacitor, a first resistor, a second resistor, a third resistor and a reading coil; the switch, the first capacitor, the second capacitor, the first resistor, the second resistor and the readout coil are connected in series, and the second capacitor is connected with the third resistor in parallel and grounded; the time-frequency domain conversion unit consists of a field programmable logic gate array and a high-speed ADC module.

2. An LC sensor time domain readout system of claim 1, wherein: the switch of the switching circuit module in the readout circuit adopts a voltage-controlled analog switch MAX4644.

3. An LC sensor time domain readout system as in claim 1 wherein: the readout coil adopts a planar single spiral inductor printed on a PCB circuit board.

4. An LC sensor time domain readout system as in claim 1 wherein: the field programmable logic gate array adopts an MSXBO Mike MA703FA-35T development board.

5. An LC sensor time domain readout system of claim 1, wherein: the high-speed ADC module consists of a DAQ4225 high-speed ADC chip and an ADS4225 low-power-consumption high-performance analog-to-digital conversion chip.

6. An LC sensor time domain readout system as in claim 1 wherein: the display unit comprises an MA703FA-35T development board, a display screen and an HDMI interface.