CN210154593U

CN210154593U - High-sensitivity capacitance sensing array detection circuit

Info

Publication number: CN210154593U
Application number: CN201920712801.9U
Authority: CN
Inventors: 叶勇; 裴向东; 刘雨婷; 郭卫卫; 苏安鑫; 韩春峰
Original assignee: LYULIANG MILITARY AND CIVILIAN INTEGRATION COLLABORATIVE INNOVATION RESEARCH INSTITUTE
Current assignee: LYULIANG MILITARY AND CIVILIAN INTEGRATION COLLABORATIVE INNOVATION RESEARCH INSTITUTE
Priority date: 2019-05-18
Filing date: 2019-05-18
Publication date: 2020-03-17
Anticipated expiration: 2029-05-18

Abstract

The utility model relates to a high-sensitivity capacitance sensing array detection circuit, which belongs to the technical field of capacitance sensor signal detection, and particularly comprises a driving circuit connected with the input end of a capacitance sensor array through an analog switch circuit, the output end of the capacitance sensor array is connected with the signal input end of a C/V conversion circuit through the analog switch circuit, the signal output end of the C/V conversion circuit is connected with a subtraction circuit through a rectification and filtering circuit, the signal output end of the subtraction circuit is connected with an amplifying and filtering circuit, the signal input end of the analog switch circuit is connected with an MCU processor, the MCU processor is connected with the subtraction circuit through a DAC circuit, the utility model obtains the sensitive change value of a sensor by subtracting the initial state signal from the measurement signal of the sensor through a controller, plays the signal blocking effect, and is more beneficial to the amplification and other treatments of useful signals, higher detection sensitivity is obtained.

Description

High-sensitivity capacitance sensing array detection circuit

Technical Field

The utility model relates to a high sensitivity's capacitance sensing array detection circuitry belongs to capacitance sensor signal detection technical field.

Background

The capacitance sensor can detect the concave-convex shape of a measurement object from a change in capacitance between a pair of electrode layers, and can be used for a surface pressure distribution sensor and a sensor such as a strain gauge. Generally, the capacitance in a capacitive sensor is represented by the following equation: c ═ 0 ∈ rS/d …, in the above formula, C denotes capacitance, ∈ 0 denotes the permittivity in free space, ∈ r denotes the relative permittivity of the dielectric layer, S denotes the area of the electrode layer, and d denotes the distance between the electrodes.

However, although the conventional capacitor blocking is convenient, there is signal delay, and the conventional capacitor blocking is only suitable for single-path signal independent operation, and is not suitable for signal processing of multi-channel signal switching, and crosstalk of switching signals is easily caused.

SUMMERY OF THE UTILITY MODEL

For solving the technical problem that prior art exists, the utility model provides a capacitance sensing array detection circuitry of high sensitivity, its measured signal and the initial condition signal that passes through the controller with the sensor subtract obtains the sensitive change value of sensor, plays the signal and separates the straight effect, can more be favorable to the processing such as enlarging of useful signal like this, obtains higher detectivity.

In order to achieve the above object, the technical solution of the present invention is a high-sensitivity capacitance sensor array detection circuit, which comprises a driving circuit, a capacitance sensor array, an analog switch circuit, a C/V conversion circuit, a rectification and filtering circuit, a subtraction circuit, a DAC circuit, an amplification and filtering circuit, and an MCU processor, the drive circuit is connected with the input end of the capacitance sensor array through the analog switch circuit, the output end of the capacitance sensor array is connected with the signal input end of the C/V conversion circuit through the analog switch circuit, the signal output end of the C/V conversion circuit is connected with the subtraction circuit through the rectification and filtering circuit, the signal output end of the subtraction circuit is connected with an amplifying and filtering circuit, the signal input end of the analog switch circuit is connected with the MCU processor, and the MCU processor is connected with the subtraction circuit through the DAC circuit.

Preferably, the driving circuit comprises an active oscillator and a low-pass filter circuit, wherein the active oscillator is used for providing 1MHz alternating current signals, and after filtering processing of the low-pass filter circuit, sinusoidal voltages of 1MHz and 1V are obtained.

Preferably, the analog switch circuit adopts an ADG1212 which supplies power with +/-15V and two channels.

Preferably, the DAC circuit adopts AD5761R, and the output voltage is 0-20 v.

Compared with the prior art, the utility model discloses following technological effect has: the utility model discloses to the signal processing of short range capacitive sensor array and the detection circuitry who designs, can more conveniently handle for direct current signal with the alternating current signal rectification that capacitive sensor's sensitive receiving terminal received. In addition, the circuit subtracts the measuring signal of the sensor from the initial state signal through the controller to obtain the sensitivity change value of the sensor, so that the signal blocking effect is achieved, the processing such as amplification of useful signals can be facilitated, and the higher detection sensitivity can be obtained. In addition, although the conventional capacitor is convenient to block, signal delay exists, and the capacitor is only suitable for single-path signal independent work, is not suitable for signal processing of multi-channel signal switching, and easily causes crosstalk of switching signals. The utility model discloses a these shortcomings that evade traditional electric capacity and block straight that can be fine height can all test electric capacity sensor's transient state and static state moreover, more are applicable to the detection of electric capacity sensor array signal.

Drawings

Fig. 1 is a block diagram of the detection circuit of the middle capacitive sensor array of the present invention.

Fig. 2 is a circuit diagram of the C/V conversion circuit, the rectifying and filtering circuit, and the subtraction circuit of the present invention.

Detailed Description

In order to make the technical problem, technical solution and advantageous effects to be solved by the present invention more clearly understood, the following description is given in conjunction with the accompanying drawings and embodiments to illustrate the present invention in further detail. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

As shown in fig. 1 and fig. 2, a high-sensitivity capacitance sensor array detection circuit comprises a driving circuit 1, a capacitance sensor array 2, an analog switch circuit 3, a C/V conversion circuit 4, the drive circuit 2 is connected with the input end of the capacitive sensor array 2 through the analog switch circuit 3, the output end of the capacitive sensor array 2 is connected with the signal input end of the C/V conversion circuit 4 through the analog switch circuit, the signal output end of the C/V conversion circuit 4 is connected with the subtraction circuit 6 through the rectification and filter circuit 5, the signal output end of the subtraction circuit 6 is connected with the amplification and filter circuit 8, the signal input end of the analog switch circuit 3 is connected with the MCU processor 9, and the MCU processor 9 is connected with the subtraction circuit 6 through the DAC circuit 7.

The driving circuit 1 comprises an active oscillator and a low-pass filter circuit, wherein the active oscillator is used for providing 1MHz alternating current signals, and 1MHz and 1V sinusoidal voltage is obtained after filtering processing of the low-pass filter circuit, so that field energy of a sensitive space is improved. The analog switch circuit 3 adopts ADG1212, the power supply of the ADG1212 is +/-15V, the on-state capacitance of the ADG1212 is smaller and is 1pF, the influence on a subsequent capacitance sensor is smaller, and different driving and sensitive electrode time-sharing multiplexing work can be met by controlling channel switching. The DAC circuit 7 adopts AD5761R, the output voltage is 0-20v, the conversion speed of the chip is high, and the setup time is only about 10 us. In addition, the DAC precision is high (16 bits), the direct output voltage can reach 20V, other auxiliary circuits are not needed, and the design is simple. The DAC can maintain the continuous output of the value of the initial voltage, unlike the signal processing in which the capacitive dc blocking circuit is transient. Therefore, the utility model discloses a detection circuitry can all measure the transient state and the static state of sensor.

A signal processing method of a high-sensitivity capacitance sensing array detection circuit is carried out according to the following steps,

a. the C/V conversion circuit converts alternating current excitation current received by the sensitive end of the sensor into an alternating voltage signal, and the initial excitation voltage is set as V_i(t) the feedback resistance of the circuit is R₁And not lower than 33k omega, and the output voltage V after C/V conversion₁(t) is:

b. the rectification and filtering circuit mainly realizes rectification of an alternating voltage signal into a direct current signal, half-wave rectification is carried out through a diode to obtain an alternating current signal with a positive half period, then the direct current signal is obtained through a second-order positive feedback active filter, and the output voltage V of the rectification and filtering circuit₂Comprises the following steps:

wherein, V_i，V₁η is the rectification efficiency of half-wave rectification signal, which is related to the diode parameter and the signal frequency, and is the amplitude of the excitation signal and the output signal of the C/V conversion circuit, and the rectification efficiency is usually 45% -98%;

c. the subtraction circuit and the DAC circuit mainly realize the DC blocking of the DC signal by firstly rectifying the detection signal sensed by each initial capacitor of the capacitor sensor array and filtering the output value V of the circuit₃Making measurementsConverting the measured voltage value into the digital value of the corresponding DAC, then when the analog switch is switched to the corresponding channel, the DAC outputs the initial voltage value of the corresponding channel at the same time, and subtracting the initial voltage value by a subtraction circuit to obtain the change value of the sensitive signal of the capacitance sensor, and the output voltage V of the change value₄Comprises the following steps:

let initial capacitance value of sensor be C_x0Then, the above formula is:

from the above equation, the detection circuit detects the capacitance change value of the sensor. The subsequent amplifying and filtering circuit can directly amplify the signal change value, so that the situation that the signal is easily saturated by directly amplifying the signal can be avoided, and higher detection sensitivity is obtained.

The foregoing is considered as illustrative and not restrictive of the preferred embodiments of the invention, and any modifications, equivalents and improvements made within the spirit and principles of the invention are intended to be included within the scope of the invention.

Claims

1. A high sensitivity capacitance sensor array detection circuit, characterized by: the capacitive sensor comprises a driving circuit, a capacitive sensor array, an analog switch circuit, a C/V conversion circuit, a rectification and filtering circuit, a subtraction circuit, a DAC circuit, an amplification and filtering circuit and an MCU processor, wherein the driving circuit is connected with the input end of the capacitive sensor array through the analog switch circuit, the output end of the capacitive sensor array is connected with the signal input end of the C/V conversion circuit through the analog switch circuit, the signal output end of the C/V conversion circuit is connected with the subtraction circuit through the rectification and filtering circuit, the signal output end of the subtraction circuit is connected with the amplification and filtering circuit, the signal input end of the analog switch circuit is connected with the MCU processor, and the MCU processor is connected with the subtraction circuit through the DAC circuit.

2. A highly sensitive capacitive sense array detection circuit according to claim 1, wherein: the driving circuit comprises an active oscillator and a low-pass filter circuit, wherein the active oscillator is used for providing 1MHz alternating current signals, and sinusoidal voltages of 1MHz and 1V are obtained after filtering processing of the low-pass filter circuit.

3. A highly sensitive capacitive sense array detection circuit according to claim 1, wherein: the analog switch circuit adopts ADG1212, and the power supply of the analog switch circuit is +/-15V and two channels.

4. A highly sensitive capacitive sense array detection circuit according to claim 1, wherein: the DAC circuit adopts AD5761R, and the output voltage is 0-20 v.