CN218298375U

CN218298375U - Distributed electrical impedance synchronous measurement system based on integrated electrodes

Info

Publication number: CN218298375U
Application number: CN202122565071.4U
Authority: CN
Inventors: 陈晓艳; 王迪; 杨永政; 王子辰; 张新宇; 付荣
Original assignee: Tianjin University of Science and Technology
Current assignee: Tianjin University of Science and Technology
Priority date: 2021-10-25
Filing date: 2021-10-25
Publication date: 2023-01-13
Anticipated expiration: 2031-10-25

Abstract

The utility model relates to a distributed electrical impedance synchronous measurement system based on electrode integrates, connect gradually by integrating electrode, FPGA master controller and host computer and form, integrated electrode comprises electrode, chip AD5940, pressure flow converting circuit, power module and peripheral circuit thereof, what FPGA adopted is the artist-7 series FPGA of Xilinx company. The utility model relates to a distributed impedance synchronous measurement system based on integrated electrode compares with system in the past, has adopted the electrode that integrates, can realize a plurality of electrodes synchronous acquisition, has advantages such as simple structure, integrated level height, stability are good, measuring range is wide, portable.

Description

Distributed electrical impedance synchronous measurement system based on integrated electrode

Technical Field

The utility model belongs to biomedical engineering and industrial measurement field, the inside electrical impedance measurement of the field territory is surveyed in concretely relates to boundary closure, especially a distributed electrical impedance synchronous measurement system and method based on integrate electrode.

Background

The basic principle of the Electrical Impedance Tomography (EIT) technology is a Tomography method based on an electromagnetic field sensitivity mechanism, electrical excitation is applied to the boundary of a measured object, the Electrical response of the object is measured, and the Electrical Impedance distribution in the field is obtained through the back-stepping calculation of an image reconstruction algorithm, so that the visual measurement is realized. The EIT implementation mode is that a certain number of electrodes are placed on the closed boundary of a measured object, voltage or current signals output by a data acquisition device are firstly applied to the measured object through 2 electrodes, then induction signals on other electrodes are measured, the measured induction signals are filtered and processed by amplitude extraction, and finally the signals are transmitted to an upper computer to realize the internal impedance distribution imaging of a measured field by utilizing an image reconstruction algorithm. Therefore, the electrical impedance measurement has the advantages of non-invasion, no damage, small volume, low cost, functional imaging and the like.

However, the existing electrical impedance measurement system is generally composed of a plurality of modules, including an electrode, a multiplexer, an acquisition system and the like, the electrode is connected with a data acquisition device by a cable, the stray capacitance of the system is unstable, the signal-to-noise ratio of the system is influenced, the improvement of the frequency of an excitation signal is inhibited, the multiplexer switches a measurement channel, the noise interference is increased, and the channel establishment time influences the measurement speed; these make the system structure complicated, the integration level is low, the interference killing feature is poor, portable.

SUMMERY OF THE UTILITY MODEL

The utility model aims at overcoming prior art's weak point, providing a distributed impedance synchronous measurement system of electrode that integrates of high integration degree, interference killing feature reinforce, portable.

Realize the utility model discloses a purpose technical scheme does:

a distributed electrical impedance synchronous measurement system based on integrated electrodes comprises a plurality of integrated electrodes, a controller and an upper computer, wherein the upper computer is connected with the controller, and the controller is respectively connected with the plurality of integrated electrodes;

the integrated electrode comprises an electrode, a chip AD5940, a voltage-current conversion circuit, a power supply module and a peripheral circuit thereof, wherein the excitation end of the chip AD5940 is connected with the voltage-current conversion circuit, the voltage-current conversion circuit is connected with the electrode, and the electrode is connected with PGA of the chip AD 5940.

The controller synchronously configures AD5940 chips on a plurality of integrated electrodes through a bus, so that two integrated electrodes generate excitation signals with required frequency, other integrated electrodes are used as measuring electrodes, and finally, data obtained by measurement are filtered, amplitude is extracted and processed and then transmitted to an upper computer through a serial port;

the upper computer can realize data analysis, curve drawing and image reconstruction according to the acquired data.

Further, the controller adopts an Artix-7 series FPGA of Xilinx company.

Further, the controller comprises a plurality of SPI interfaces.

Furthermore, the voltage-current conversion circuit comprises an operational amplifier and peripheral circuits thereof.

The utility model discloses an advantage is with positive effect:

1. the utility model discloses the system has adopted integrated form impedance measurement chip AD5940 and has carried out the circuit extension to it, directly links to each other electrode and measurement chip AD5940, has realized zero transmission distance, has shortened weak alternating current signal's transmission distance, and the interference killing feature is strong, reduces transmission loss, has avoided the wave reflection phenomenon, has also overcome the measuring error that alternating current excitation signal arouses because of the phase angle change simultaneously, has improved the interference killing feature and the measurement accuracy of system.

2. The utility model discloses an electrode and measuring circuit integrated design do not need multiplexer and connecting cable, and 16 total integrated electrodes distribute 16 integrated electrodes in the cross-section department of testee, and 16 integrated electrodes can be aroused in step and measure, have improved measuring speed than measurement mode in proper order, have also overcome the measuring error that alternating current excitation signal arouses because of the phase angle change simultaneously, have improved measurement accuracy.

Drawings

FIG. 1 is a frame diagram of the system of the present invention;

fig. 2 is a circuit block diagram of the integrated electrode of the present invention;

FIG. 3 is a flow chart of the method of the present invention;

fig. 4 is a circuit diagram of the voltage-current switching circuit of the present invention.

Detailed Description

The following describes embodiments of the present invention in detail with reference to the accompanying drawings; it should be noted that the present embodiment is illustrative, not restrictive, and the scope of the invention should not be limited thereto.

The distributed electrical impedance synchronous measurement system based on the integrated electrodes comprises a plurality of integrated electrodes, a controller and an upper computer, wherein the upper computer is connected with the controller, and the controller is connected with the plurality of integrated electrodes respectively.

The integrated electrode comprises an electrode, a chip AD5940, a voltage-current conversion circuit, a power supply module and a peripheral circuit thereof.

The AD5940 integrates the DDS, the ADC, the DSP microprocessor core and other units, and can directly output information of a real part, an imaginary part and the like of impedance to be detected, so that the complexity of a system is reduced, and the integration level of the system is improved.

The electrode is directly connected with the measurement chip AD5940, so that the transmission distance of weak alternating current signals is shortened, the transmission loss is reduced, the wave reflection phenomenon is avoided, and the anti-interference capability of the system is improved.

The integrated electrode is configured with a chip AD5940 through a controller FPGA to select whether the acquisition module works in a measurement mode or an excitation mode, when the integrated electrode works in the excitation mode, a voltage-current conversion circuit is needed to convert a voltage signal generated by the chip AD5940 into current excitation, and the voltage-current conversion circuit is added at an excitation end (VOUT end) of the chip AD5940, as shown in FIG. 3, a current mirror composed of an operational amplifier AD844 and peripheral circuits thereof realizes voltage-current conversion.

The system consists of 16 integrated electrodes. The chip AD5940 communicates through the SPI bus, and 16 chip AD 5940's clock signal line is connected to FPGA, produces SCLK signal by FPGA synchronization, can make 16 chip AD5940 can synchronous work.

The controller employs an Artix-7 series FPGA from Xilinx corporation. The control flow is as shown in fig. 3, the FPGA configures the chips AD5940 distributed on the 16 integrated electrodes on the cross section of the measured object through the SPI bus, so that the integrated electrode 1 and the integrated electrode 2 work in an excitation mode, and the other integrated electrodes work in a measurement mode, and then reconfigures the 16 chips AD5940, so that the integrated electrode 2 and the integrated electrode 3 work in an excitation mode, and the other integrated electrodes work in a measurement mode, so as to circulate and send the measured data to the upper computer, the FPGA transmits the measured data to the upper computer through the serial port after the data are filtered, amplitude extracted, and the like, and the upper computer can realize the functions of data analysis, curve drawing, image reconstruction, and the like according to the measured data.

The utility model discloses a theory of operation is:

the measurement system adopts an integrated impedance measurement chip AD5940 newly introduced by ADI company, and integrates DDS, ADC, DSP microprocessor core and other units together, and can directly output information of a real part, an imaginary part and the like of impedance to be measured, thereby reducing the complexity of the system and improving the integration level of the system; the DDS in the AD5940 chip generates voltage with specific frequency, the voltage is converted into current excitation with specific frequency through a voltage-current conversion circuit to excite a measured object, the induced voltage generated on the measured object is sampled by the ADC in the AD5940 chip, discrete Fourier Transform (DFT) is carried out through the DSP on the chip, a real part value and an imaginary part value obtained under the output frequency are returned after the conversion, a required impedance value is conveniently calculated according to initial calibration data, and the AD5940 chip is communicated with the FPGA through an SPI bus.

Claims

1. The utility model provides a distributed electrical impedance synchronous measurement system based on integrate electrode which characterized in that: the device comprises a plurality of integrated electrodes, a controller and an upper computer, wherein the upper computer is connected with the controller, and the controller is respectively connected with the plurality of integrated electrodes;

the integrated electrode comprises an electrode, a chip AD5940, a voltage-current conversion circuit, a power module and a peripheral circuit thereof, wherein the excitation end of the chip AD5940 is connected with the voltage-current conversion circuit, the voltage-current conversion circuit is connected with the electrode, and the electrode is connected with PGA of the chip AD 5940;

the controller synchronously configures AD5940 chips on a plurality of integrated electrodes through a bus, so that two integrated electrodes generate excitation signals with required frequency, other integrated electrodes are used as measuring electrodes, and finally, data obtained by measurement are transmitted to an upper computer through a serial port after being filtered and amplitude extraction;

2. The integrated electrode-based distributed electrical impedance synchronous measurement system of claim 1, wherein: the controller employs an Artix-7 series FPGA from Xilinx corporation.

3. The integrated electrode-based distributed electrical impedance synchronous measurement system of claim 1, wherein: the controller comprises a plurality of SPI interfaces.

4. The integrated electrode-based distributed electrical impedance synchronous measurement system of claim 1, wherein: the voltage-current conversion circuit comprises an operational amplifier and a peripheral circuit thereof.