Electrostatic coupling capacitance sensor, electrostatic coupling capacitance sensing and measurement system and measurement method

Abstract

This invention discloses an electrostatic coupling capacitance sensor, an electrostatic coupling capacitance sensing measurement system, and a measurement method. The electrostatic coupling capacitance sensor includes a working electrode, a protective electrode, and a shielding layer. The protective electrode is disposed within the shielding layer through an insulating layer, and the working electrode is disposed within the protective electrode through an insulating layer. The shielding layer is used to shield against external interference. The protective electrode is used to isolate the coupling capacitance between the working electrode and the shielding layer. The protective electrode and the working electrode maintain an equipotential state. This invention simplifies the conventional "excitation-detection" separated dual-working-electrode structure of electrostatic coupling capacitance sensors, which is beneficial for measuring jet flows outside pipes or in open spaces. It broadens the application range of electrostatic coupling capacitance sensors and improves their engineering applicability.

Description

Technical Field

[0001] This invention relates to the field of gas-solid two-phase flow measurement technology, specifically a system and method for measuring the flow parameters of charged particles based on a single-working-electrode electrostatic coupling capacitive sensor. Background Technology

[0002] Two-phase flow systems are widely used in industries such as energy, chemical, power, and metallurgy. With the development of modern industry, the requirements for the detection and control of industrial process parameters are becoming increasingly stringent. The accurate measurement of two-phase flow parameters is of great practical significance for the safe and efficient operation of industrial processes and for environmental protection.

[0003] Electrical methods, due to their advantages of being non-contact, highly reliable, low-cost, and easy to maintain, have great application potential and value in measuring parameters of gas-solid two-phase flows. Electrical measurement methods for gas-solid two-phase flows mainly include electrostatic and capacitive methods. The electrostatic method is a particle flow parameter method based on the particle charging phenomenon in gas-solid two-phase flows. It obtains particle charging information by placing an electrostatic sensor in the particle flow channel, thereby characterizing the particle flow process. The capacitive method is based on the fact that changes in the concentration (i.e., equivalent dielectric constant) of the mixture in the gas-solid two-phase flow lead to changes in the sensor capacitance value, thus transforming the problem of measuring solid phase concentration into the problem of detecting capacitance value. Currently, when using electrical methods to measure gas-solid two-phase flows, electrostatic or capacitive sensors are generally used alone to obtain electrostatic or capacitive signals. They can also be coupled to simultaneously measure electrostatic and capacitive signals in the same sensitive space. However, conventional electrostatic-coupled capacitive sensors employ a "stimulation-detection" separate dual-working-electrode structure design. This structure forms a detection channel between the excitation electrode and the detection electrode, through which the measured fluid flows. The split dual working electrode structure is poorly adapted to the measurement of large-diameter pipes. Electrodes of the corresponding size need to be manufactured according to the diameter of the pipe being measured. It is also difficult to apply to the measurement of solid phase concentration in jet flow outside pipes or open spaces. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a universally applicable electrostatic coupling capacitance sensor, electrostatic coupling capacitance sensing measurement system and measurement method based on a detection surface.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: An electrostatic coupling capacitive sensor includes a working electrode, a protective electrode, and a shielding layer. The protective electrode is disposed within the shielding layer through an insulating layer, and the working electrode is disposed within the protective electrode through an insulating layer. The shielding layer is used to shield external interference. The protective electrode is used to isolate the coupling capacitance between the working electrode and the shielding layer. The protective electrode and the working electrode maintain an equipotential state.

[0006] The working electrode is cylindrical in shape.

[0007] The opening plane of the working electrode is flush with or slightly higher than the end face of the protective electrode.

[0008] The present invention also provides an electrostatic coupling capacitance sensing and measurement system, comprising: An electrostatic coupling capacitive sensor acquires detection signals containing both capacitive and electrostatic signals. as well as The signal conditioning circuit is connected to the electrostatic coupling capacitor sensor to extract the capacitance signal and electrostatic signal from the detection signal.

[0009] The signal conditioning circuit includes a detection circuit, a low-pass filter module, a high-pass filter module, a signal amplification module, and an amplitude conversion module. The detection circuit includes an excitation source, a first operational amplifier, and a second operational amplifier. The excitation source is connected to both the protection electrode and the positive input terminal of the first operational amplifier, and is connected to the positive input terminal of the second operational amplifier via a series resistor R. The inverting input terminal of the first operational amplifier is connected to the working electrode. A feedback resistor is connected in parallel between the inverting input terminal and the output terminal of the first operational amplifier. and feedback capacitor A resistor R is connected in series with the output of the first operational amplifier and then connected to the inverting input of the second operational amplifier. A resistor of the same value is connected between the inverting input and output of the second operational amplifier, between the output and feedback common node of the first operational amplifier and the inverting input and feedback common node of the second operational amplifier, between the non-inverting input of the second operational amplifier and the excitation source, and between the second operational amplifier and ground. R ; The excitation source generates a sinusoidal excitation voltage. V s ( t )Signal; Both the low-pass filter module and the high-pass filter module are connected to the output of the second operational amplifier; the signal amplification module is connected to the output of the low-pass filter module; and the amplitude conversion module is connected to the output of the high-pass filter module.

[0010] The detection signal output by the detection circuit is:

[0011] in, This is the voltage signal at the output of the second operational amplifier; q Equivalent charge Q The amount of charge induced on the working electrode; ω is the angular frequency of the electrostatic signal;A , f and ω These represent the amplitude, frequency, and angular frequency of the sinusoidal excitation voltage signal, respectively.

[0012] After gain k 1 The output of the high-pass filter module is:

[0013] Amplitude conversion module extracts input signal The amplitude is used to obtain the capacitance signal:

[0014] After gain k 2 The output after the low-pass filter module is:

[0015] After gaining k 3 After the signal amplification module, the final electrostatic signal obtained is:

[0016] in, This is the voltage signal output by the high-pass filter module; This is the voltage signal output by the amplitude conversion module; This is the voltage signal output by the low-pass filter module; This is the voltage signal output by the signal amplification module.

[0017] The present invention also provides a method for measuring particle flow parameters, wherein the electrostatic coupling capacitance sensor of the electrostatic coupling capacitance sensing measurement system is placed on any side of the outside near the particle being measured.

[0018] The electrostatic coupling capacitive sensor is fixed to the fixture via a connector.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. The electrostatic coupling capacitive sensor proposed in this invention has a protective electrode and a working electrode with the same potential. Therefore, the protective electrode and the working electrode do not form a detection channel. Instead, the end face of a working electrode is used as the detection surface to simultaneously collect electrostatic and capacitance information in the same sensitive space. This simplifies the "excitation-detection" separate dual working electrode structure of conventional electrostatic coupling capacitive sensors, which is beneficial for measuring jet flow in non-pipe or open spaces. It can broaden the application range of electrostatic coupling capacitive sensors and improve their engineering applicability.

[0020] 2. Through the signal conditioning circuit, the electrostatic information and capacitance information collected by the sensor can be decoupled, separated and extracted. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the electrostatic coupling capacitive sensor of the present invention; Figure 2 This is a schematic diagram of the electrostatic coupling capacitance sensing measurement system; Figure 3 This is a circuit diagram of an electrostatic coupling capacitance sensing measurement system. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings: like Figure 1 As shown, the electrostatic coupling capacitive sensor provided in this embodiment includes a working electrode 1, a protective electrode 2, and a shielding layer 3. The shielding layer 3 shields external interference, and the protective electrode 2 is used to isolate the coupling capacitance between the working electrode 1 and the shielding layer 3.

[0023] Both the shielding layer and the protective electrode are open container-shaped (similar to a bowl-shaped or square groove structure). The opening size of the shielding layer must be larger than the external size of the protective electrode, allowing the protective electrode to be completely contained within the shielding layer, and the opening edge of the protective electrode must not extend beyond the opening edge of the shielding layer. The shielding layer and the protective electrode are fixed together using insulating material 4, ensuring their relative spatial stability. The working electrode is cylindrical (its cross-section can be circular or rectangular, i.e., a short cylinder or square block), and its axis is aligned with the depth direction of the protective electrode and the shielding layer (i.e., the normal direction of the opening plane). One end face of the working electrode is coplanar with the opening plane of the protective electrode and the shielding layer; that is, the same side surface of all three is on the same horizontal plane. The working electrode is enclosed by the protective electrode, and the opening size of the protective electrode is larger than the external size of the working electrode. The working electrode and the protective electrode are also fixed together using insulating material.

[0024] To ensure the shielding effect of the protective electrode, the opening plane of the protective electrode can be slightly higher than the end face of the working electrode.

[0025] The electrostatic coupling capacitive sensor provided by this invention also includes a coaxial cable, comprising, from the inside out, an inner core conductor, an insulating layer, an outer core conductor, and an insulating protective sheath. Through holes are formed at the bottom of both the shielding layer and the protective electrode. The coaxial cable 5 passes through these through holes, and the inner core conductor and outer core conductor are electrically connected to the working electrode and the protective electrode, respectively. The other end of the coaxial cable is led out to… Figure 3 The signal conditioning circuit eliminates the influence of cable coupling capacitance.

[0026] It should be noted that the shielding layer and the protective electrode are not limited to circular openings, but can also be rectangular or other concave structures, but must meet the conditions that the shielding layer completely covers the protective electrode, the protective electrode completely covers the working electrode, and the three are coplanar or the plane of the protective electrode opening is slightly higher than the end face of the working electrode; the working electrode is not limited to a short cylindrical shape, but can also be a column with a rectangular cross-section.

[0027] Example 2 This embodiment provides an electrostatic coupling capacitance sensing measurement system, including the electrostatic coupling capacitance sensor and signal conditioning circuit provided in Embodiment 1.

[0028] Figure 3 This is a schematic diagram of the signal conditioning circuit for an electrostatic coupling capacitive sensing measurement system.

[0029] The signal conditioning circuit includes a detection circuit, a low-pass filter module, a high-pass filter module, a signal amplification module, and an amplitude conversion module.

[0030] The detection circuit includes an excitation source, operational amplifier 1, and operational amplifier 2. The excitation source is connected to both the protection electrode and the positive input terminal of operational amplifier 1. A resistor R is connected in series with the excitation source and then connected to the positive input terminal of operational amplifier 2. The inverting input terminal of operational amplifier 1 is connected to the working electrode; a feedback resistor is connected in parallel between the inverting input terminal and the output terminal of operational amplifier 1. and feedback capacitor A resistor R is connected in series with the output of operational amplifier 1 and then connected to the inverting input of operational amplifier 2. A resistor of the same value is connected between the inverting input and output of operational amplifier 2, between the output and feedback common node of operational amplifier 1 and the inverting input and feedback common node of operational amplifier 2, between the non-inverting input of operational amplifier 2 and the excitation source, and between operational amplifier 2 and ground. R。 The excitation source generates a sinusoidal excitation voltage. V s ( t )Signal.

[0031] Both the low-pass filter module and the high-pass filter module are connected to the output of operational amplifier 2; the signal amplification module is connected to the output of the low-pass filter module; and the amplitude conversion module is connected to the output of the high-pass filter module.

[0032] By simultaneously detecting the capacitance and particle charge information between the working electrode and "ground" using a single working electrode, the structure is more compact, which is beneficial for expanding the measurement application scenarios of electrostatic coupling capacitive sensors and improving their engineering applicability.

[0033] The electrostatic coupling capacitive sensing measurement system provided by this invention generates a capacitance signal on the working electrode when solid particles transported by gas pass through the electrostatic coupling capacitive sensor. This capacitance signal is proportional to the capacitance between the working electrode and "ground," and it increases monotonically with the particle concentration. On the other hand, the particles acquire a certain amount of charge due to collisions and friction between particles and between particles and the pipe during their movement. Based on the principle of electrostatic induction, the working electrode can obtain an electrostatic signal related to the particle charge. Therefore, the working electrode simultaneously obtains both capacitance and electrostatic signals. A signal conditioning circuit is used to decouple and extract the capacitance and electrostatic signals. Here, "ground" can be the actual boundary of the metal pipe or an infinite distance in open space.

[0034] The working electrode is directly connected to the inverting input terminal of operational amplifier 1, with a sinusoidal excitation voltage. V s ( t A voltage is applied to the non-inverting input terminal of operational amplifier 1. Due to the "virtual open" and "virtual short" characteristics of operational amplifiers, there is no current between its non-inverting and inverting input terminals, but their potentials are equal. Therefore, the voltage at its inverting input terminal is equal to... V s ( t To isolate the influence of the coupling capacitance between the working electrode and the shielding layer on the measurement, a protective electrode placed between the working electrode and the shielding layer needs to maintain an equipotential state with the working electrode, i.e., the excitation voltage... V s ( t Connecting it to the positive input of operational amplifier 1 ensures no current flows between the working electrode and the protection electrode. Therefore, the capacitance between the working electrode and the protection electrode... C 1. Capacitance between the protective electrode and the shielding electrode C 2. This will not affect the current flowing from the working electrode to the inverting input of operational amplifier 1. I This provides protection.

[0035] If the amplitude, frequency, and angular frequency of the sinusoidal excitation voltage signal are denoted as follows: A , f and ω When gas carries solid particles past the working electrode of the sensor, it is assumed that the equivalent charge carried by the particles is... Q The capacitance between the working electrode and "ground" is Based on the fact that the current flowing through the working electrode is equal to the current flowing through the feedback resistor... and feedback capacitor The sum of the currents can be obtained as follows:

[0036]

[0037] in, q Equivalent charge Q The amount of charge induced on the working electrode This is the angular frequency of the electrostatic signal. It is marked as [symbol missing] in the signal conditioning circuit. R The resistors are resistors with the same resistance value.

[0038] In actual measurement, the excitation signal The high-frequency AC voltage used is typically on the order of 1 MHz, inducing charge. q The frequency is related to the sensor electrode size and the particle conveying speed, and is usually in the low-frequency range, generally on the order of 10~100 Hz. Therefore, the output voltage... V A high-pass filter module and a low-pass filter module can then be connected in parallel to extract the two signals from different frequency bands.

[0039] The lower cutoff frequency of the high-pass filter module is set on the order of 10kHz. This allows for the extraction of the capacitance signal component while filtering out the electrostatic signal component, thus ensuring the reliability of subsequent capacitance signal conversion. Therefore, after a gain of... k 1 The output of the high-pass filter module is:

[0040] The amplitude conversion module can extract the amplitude of the input signal to obtain the capacitance signal.

[0041] The upper cutoff frequency of the low-pass filter module needs to be set on the order of 10kHz to ensure complete filtering of high-frequency capacitor signals while retaining the complete electrostatic signal component. If its gain is... k 2 The output will be:

[0042] After gaining k 3 After the signal amplification module, the final electrostatic signal obtained is:

[0043] The signal detection circuit designed above can simultaneously acquire electrostatic and capacitance information from the working electrode, realizing the coupled development of a single-working-electrode electrostatic and capacitance sensor. Using this single-working-electrode sensor, electrostatic and capacitance information can be acquired simultaneously within the same sensitive area.

Claims

1. An electrostatic coupling capacitive sensor, characterized in that, It includes a working electrode, a protective electrode, and a shielding layer. The protective electrode is disposed within the shielding layer through an insulating layer, and the working electrode is disposed within the protective electrode through an insulating layer. The shielding layer is used to shield external interference. The protective electrode is used to isolate the coupling capacitance between the working electrode and the shielding layer. The protective electrode and the working electrode maintain an equipotential state.

2. The electrostatic coupling capacitive sensor according to claim 1, characterized in that, The working electrode is cylindrical in shape.

3. The electrostatic coupling capacitive sensor according to claim 1, characterized in that, The opening plane of the protective electrode is flush with or slightly higher than the end face of the working electrode.

4. The electrostatic coupling capacitive sensor according to claim 1, characterized in that, It also includes a coaxial cable; the coaxial cable includes an inner core conductor, an insulation layer, an outer core conductor, and an insulating protective sheath layer arranged sequentially from the inside to the outside; through holes are opened at the bottom of the shielding layer and the protective electrode; the coaxial cable is inserted through the through holes, and the inner core conductor and the outer core conductor are electrically connected to the working electrode and the protective electrode, respectively, to eliminate the influence of cable coupling capacitance.

5. An electrostatic coupling capacitance sensing and measurement system, characterized in that, include: The electrostatic coupling capacitive sensor according to any one of claims 1-4 acquires a detection signal carrying both a capacitance signal and an electrostatic signal; as well as The signal conditioning circuit is connected to the electrostatic coupling capacitor sensor to extract the capacitance signal and electrostatic signal from the detection signal.

6. The electrostatic coupling capacitance sensing and measurement system according to claim 5, characterized in that, The signal conditioning circuit includes a detection circuit, a low-pass filter module, a high-pass filter module, a signal amplification module, and an amplitude conversion module. The detection circuit includes an excitation source, a first operational amplifier, and a second operational amplifier. The excitation source is connected to both the protection electrode and the positive input terminal of the first operational amplifier, and is connected to the positive input terminal of the second operational amplifier via a series resistor R. The inverting input terminal of the first operational amplifier is connected to the working electrode. A feedback resistor is connected in parallel between the inverting input terminal and the output terminal of the first operational amplifier. and feedback capacitor A resistor R is connected in series with the output of the first operational amplifier and then connected to the inverting input of the second operational amplifier. A resistor of the same value is connected between the inverting input and output of the second operational amplifier, between the output and feedback common node of the first operational amplifier and the inverting input and feedback common node of the second operational amplifier, between the non-inverting input of the second operational amplifier and the excitation source, and between the second operational amplifier and ground. R ; The excitation source generates a sinusoidal excitation voltage. V s ( t )Signal; Both the low-pass filter module and the high-pass filter module are connected to the output of the second operational amplifier; the signal amplification module is connected to the output of the low-pass filter module; and the amplitude conversion module is connected to the output of the high-pass filter module.

7. The electrostatic coupling capacitance sensing and measurement system according to claim 6, characterized in that, The detection signal output by the detection circuit is: in, This is the voltage signal at the output of the second operational amplifier; q Equivalent charge Q The amount of charge induced on the working electrode; ω is the angular frequency of the electrostatic signal; A , f and ω These represent the amplitude, frequency, and angular frequency of the sinusoidal excitation voltage signal, respectively.

8. The electrostatic coupling capacitance sensing and measurement system according to claim 7, characterized in that, After gain k 1 The output of the high-pass filter module is: Amplitude conversion module extracts input signal The amplitude is used to obtain the capacitance signal: After gain k 2 The output after the low-pass filter module is: After gaining k 3 After the signal amplification module, the final electrostatic signal obtained is: in, This is the voltage signal output by the high-pass filter module; This is the voltage signal output by the amplitude conversion module; This is the voltage signal output by the low-pass filter module; This is the voltage signal output by the signal amplification module.

9. A method for measuring particle flow parameters based on the electrostatic coupling capacitive sensing measurement system according to any one of claims 5-8, characterized in that, The electrostatic coupling capacitance sensor of the electrostatic coupling capacitance sensing measurement system is placed on any external side near the flow of the particle being measured.

10. The method for measuring particle flow parameters according to claim 9, characterized in that, The electrostatic coupling capacitive sensor is fixed to the fixture via a connector.

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