CN106872535A

CN106872535A - New E CT data collecting systems

Info

Publication number: CN106872535A
Application number: CN201510927258.0A
Authority: CN
Inventors: 李福来
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-12-14
Filing date: 2015-12-14
Publication date: 2017-06-20

Abstract

Key control unit of the new E CT data collecting systems using field programmable gate array (FPGA) as ECT data collecting systems, also including several classes of control arrays of sensor, C/V conversions, differential amplification, A/D conversions, compensation, USB interface, PC.It effectively can be adjusted to output signal amplitude and frequency.Capacitance sensor pole plate switching circuit is controlled by FPGA, space-saving while reduce system component cost, and the link time expense such as LPF can be reduced by digital demodulation.Because MAC working frequencies are higher than ADC sample frequencys, the next cycle after A/D is converted just can obtain demodulation result, improve the speed and accuracy of data acquisition.

Description

New E CT data collecting systems

Art

The present invention relates to a kind of data collecting system, especially a kind of new E CT data collecting systems.

Background technology

Electrical capacitance tomography (ECT) is a process tomographic imaging technology based on capacitance-sensitive principle.The features such as it has fast response time and tested logistics noncontact, simple installation and low cost, the two dimension or three-dimensional visualization information of closed vessel and pipeline internal flows situation can be provided, a kind of technology for having very much a development potentiality is had become in the Visual retrieval application of industrial process parameter.

At present, ECT systems are mainly made up of multielectrode capacitance sensor, data collecting system and tomography computer etc., and wherein data acquisition is the most key intermediate link.According to current technology, the maximum image taking speed of ECT detector systems is about 100 frames/s, it is difficult to ensure the real-time of imaging system.Substantial amounts of analog device, such as analog demodulator and analog filter are used in data collecting system because being limited by itself accuracy and other factors are disturbed, the accuracy of measurement is more difficult to ensure that.

The content of the invention

The present invention proposes a kind of new E CT data collecting systems, improves the speed and accuracy of data acquisition.

The technical solution adopted in the present invention is：Key control unit of the new E CT data collecting systems using field programmable gate array (FPGA) as ECT data collecting systems, also including several classes of control arrays of sensor, C/V conversions, differential amplification, A/D conversions, compensation, USB interface, PC.

FPGA controls the generation of ac-excited voltage signal as the control unit of system；Control conversion of each electrode between three states (excitation, detection and ground connection)；Coordinate the sampling clock of A/D conversions.When the circuit measuring of a cycle is started, the controls of FPGA first produce ac-excited voltage-drop loading to exciting electrode, then the capacitance between electrode pair is chosen in detection, magnitude of voltage is converted thereof into by C/V change-over circuits, the direct analog/digital conversion of magnitude of voltage that will be exported with A/D change-over circuits, then digitized data are carried out into digital demodulation inside FPGA, after demodulation is completed, by result make a gift to someone FIFO caching in, required data are sent into tomography computer finally by USB parallel interfaces carries out the reconstruction of image.

The FPGA includes memory, regulation wave filter, DDS signal generator, controlling plate switching circuit.

DDS signal generator is under the driving of reference clock, phase accumulator carries out linear adding up to frequency control word, the phase code for obtaining is addressed to wave memorizer, it is allowed to export corresponding amplitude code, corresponding staircase waveform is obtained by A/D converter, this staircase waveform is smoothed using low pass filter finally, required Frequency Smooth, the continuous signal of waveform is finally drawn.

ECT data collecting systems pole plate control circuit is carried out using serial detection pattern.When being measured to capacitance sensor by the way of the detection of three electrode excitation bipolar electrodes, i.e. when electrode combination 1 is for excitation, driving voltage is loaded on electrode 1,2,3 these three pole plates, and detection circuit is connected to above pole plate 4,5, and remaining those battery lead plate is then grounded.Sampling is circulated to other electrodes according to permutation and combination principle, until 192 different values are all measured, the measurement of a cycle is just completed.Each electrode plate of capacitance sensor has three kinds of mode of operations, is respectively the battery lead plate as excitation, the battery lead plate as detection, and electrode plate earthing.

Circuit is controlled to switch over battery lead plate different operating mode using battery lead plate.Using the ECT capacitance sensors of 16 electrodes, because each pole plate has three controlling switches, therefore a total of 48 electronic switches are controlled to pole plate.48 pins chosen on FPGA are controlled to this 48 electronic switches respectively.Inside FPGA, under the control of clock, not different pins or for high level or be low level in the same time, so that control the closure of electronic switch and disconnect, to reach the switching of pole plate working method.

ECT detector system digital demodulations refer to is sampled by analog (A/D) converter to the signal by C/V change-over circuits, then digitized signal is sent to high performance digital signal processor, the amplification value and corresponding phase information of measured signal is calculated in the algorithm of processor inner utilization numerical computations.The method that module is demodulated using orthogonal sequence, the demodulation method is that the correlation theory of matched filter is applied into the inside.Matched filter is belonging to linear filter in principle, the signal to noise ratio of output is reached maximum under the influence of white noise.

The beneficial effects of the invention are as follows：Effectively output signal amplitude and frequency can be adjusted using the ECT data collecting systems based on FPGA.Capacitance sensor pole plate switching circuit is controlled by FPGA, space-saving while reduce system component cost, and the link time expense such as LPF can be reduced by digital demodulation.Because MAC working frequencies are higher than ADC sample frequencys, the next cycle after A/D is converted just can obtain demodulation result, improve the speed and accuracy of data acquisition.

Brief description of the drawings

The present invention is further described with reference to the accompanying drawings and examples.

Fig. 1 is new E CT DATA REASONINGs and acquisition system figure.

Fig. 2 is that each electrode is used alone a C/V change-over circuit figure.

Fig. 3 is that all of electrode is used in conjunction with a C/V change-over circuit figure.

Specific embodiment

The invention will be further described with reference to the accompanying drawings and examples.

Such as Fig. 1, key control unit of the new E CT data collecting systems using field programmable gate array (FPGA) as ECT data collecting systems, also include several classes of control arrays of sensor, C/V conversions, differential amplification, A/D conversions, compensation, USB interface, PC.

Such as Fig. 2, Fig. 3, in electrode control circuit, when driving voltage is loaded into electrode i, detection circuit is connected to electrode, when, then electronic switch S2i, S1, closes, electronic switch S1i, S2f, Sei, Sei disconnection.When driving voltage is loaded into electrode J, and detect that circuit is connected to when on electrode i, electronic switch S2f, S1i closure, electronic switch S1i, S2i, Sei, Sei disconnect.

Claims

1.It is new ECT Data collecting system is with field programmable gate array (FPGA) As ECT The key control unit of data collecting system, also including several classes of control arrays of sensor, C/V Conversion, differential amplification, A/D Change, compensate, USB Interface, PC Machine.

2.According to claim 1 Described is new ECT Data collecting system, it is characterized in that described FPGA Including memory, regulation wave filter, DDS Signal generator, controlling plate switching circuit.

3.According to claim 1 Described is new ECT Data collecting system, it is characterized in that described ECT Data collecting system pole plate control circuit is carried out using serial detection pattern.

4.According to claim 1 Described is new ECT Data collecting system, it is characterized in that described ECT Detector system digital demodulation refers to by analog (A / D) Converter is to passing through C / V The signal of change-over circuit is sampled, then digitized signal is sent to high performance digital signal processor, the amplification value and corresponding phase information of measured signal, the method that module is demodulated using orthogonal sequence are calculated in the algorithm of processor inner utilization numerical computations.