Material contact type powder static monitor

Abstract

The utility model discloses a material contact type powder static monitor which comprises a Faraday cup and a detection unit. The detection unit is electrically connected with the outer wall of the Faraday cup; the detection unit is used for carrying out discharging operation, measuring interference charges and measuring total charges of the Faraday cup in sequence in a detection time period; and calculating the induced charge of the Faraday cup according to the interference charge, the measurement time of the interference charge, the total charge and the measurement time of the total charge. According to the utility model, signal interference caused by contact of materials with the Faraday cup can be solved, so that the measurement result is more accurate.

Description

Technical Field

[0001] The utility model relates to the technical field of mechanical automation, and particularly relates to a material-contact type powder electrostatic monitor. Background Art

[0002] In the production process of chemical powder materials represented by PE, PP, and EVI, the pneumatic conveying link can make the high-volume resistivity powder materials carry 1 - 5 μC / kg or higher static electricity. At the same time, the granular material pneumatic conveying link contains a certain content of polymer dust such as filaments and broken particles. At the same time, the chemical powder may also be accompanied by the escape of combustible monomer gases represented by polymer monomers such as ethylene and propylene. The critical value for the bin not to generate electrostatic discharge is 0.1 - 0.2 μC / kg. The above situation causes a high incidence of explosion accidents in petrochemical powder bins caused by electrostatic discharge.

[0003] Petrochemical powder production has extensive safety requirements for the continuous detection of the material static electricity level in the powder production process. Sampling with a cylinder-driven Faraday cup, such as Patent ZL201920679427.7, can only achieve intermittent detection of materials. The detection data has a long interval and cannot form real-time continuous data. And the cylinder-type sampling electrostatic detection may occur material jamming, and the cylinder may be stuck during advancement or retraction, resulting in material sampling failure. At the same time, the sampling cup inside the pneumatic conveying pipeline forms a protrusion. Under the high-speed material flow, the protruding sampling cup can cause a large number of broken particles and increase the granular dust concentration. From the perspective of evaluating the pneumatic conveying dust concentration and broken particle control, the cylinder-type sampling electrostatic monitoring should not be carried out frequently.

[0004] In the prior art, in Patents ZL201510994330.1 and ZL201810478603.0, a simulated Faraday cup structure is used to detect the powder static electricity, which innovatively supports the direct contact of the material with the inner wall of the Faraday cup. However, the above patents do not disclose a solution to the signal interference problem caused by the material contacting the Faraday cup. In the powder production pipeline with a gas explosion hazard, a large area of exposed insulating material is not allowed. The method of covering an insulating film inside the simulated Faraday cup is not allowed to be used in the pneumatic conveying link of petrochemical powder production. Summary of the Utility Model

[0005] The purpose of the utility model is to provide a material-contact type powder electrostatic monitor to solve the deficiencies in the prior art. It can solve the problem of interfering charges generated by the material contacting the Faraday cup and make the measurement result more accurate.

[0006] The utility model provides a material-contact type powder electrostatic monitor, which includes a Faraday cup and a detection unit;

[0007] The detection unit is electrically connected to the outer wall of the Faraday cup;

[0008] The detection unit is configured to perform a discharging operation, measure interfering charges, and measure the total charge of the Faraday cup in sequence during a detection period;

[0009] Calculate the induced charge of the Faraday cup based on the interfering charges, the measurement time of the interfering charges, the total charge, and the measurement time of the total charge.

[0010] The material-contact type powder electrostatic monitor as described above, wherein, optionally, the detection unit includes an operational amplifier, a discharging branch, a first detection branch, and a second detection branch;

[0011] The non-inverting input terminal of the operational amplifier is electrically connected to the outer wall of the Faraday cup, and the inverting input terminal of the operational amplifier is electrically connected to its output terminal;

[0012] One end of the discharging branch is electrically connected to the wire, and the other end is grounded;

[0013] One end of the first detection branch is electrically connected to the wire, and the other end is grounded;

[0014] One end of the second detection branch is electrically connected to the wire, and the other end is grounded.

[0015] The material-contact type powder electrostatic monitor as described above, wherein, optionally, the first detection branch is composed of a first detection switch and a detection resistor connected in series; the first detection switch is a normally open switch and is configured to close when measuring the interfering charges.

[0016] The material-contact type powder electrostatic monitor as described above, wherein, optionally, the discharging branch is composed of a discharging switch and a discharging resistor connected in series;

[0017] The second detection branch is composed of a second detection switch and a detection capacitor connected in series; the second detection switch is a normally closed switch and is configured to open when detecting the interfering charges.

[0018] The material-contact type powder electrostatic monitor as described above, wherein, optionally, when the discharging operation is completed, the remaining charge amount of the detection capacitor is not greater than 0.1% of the original charge amount.

[0019] The material-contact type powder electrostatic monitor as described above, wherein, optionally, during the process of measuring the interfering charges, the calculation formula for the interfering charges is:

[0020]

[0021] wherein, V rem is the voltage across the detection resistor during the process of measuring the interfering charges, R rem is the resistance value of the detection resistor, and t is the detection duration of the interfering charges.

[0022] The material-contact type powder electrostatic monitor as described above, optionally, further includes an outer cylinder, the outer cylinder is sleeved on the outer periphery of the Faraday cylinder, and is insulated from the Faraday cylinder; the outer cylinder is grounded.

[0023] The material-contact type powder electrostatic monitor as described above, optionally, further includes an explosion-proof chamber and a detection board;

[0024] The explosion-proof chamber is located on the outer periphery of the outer cylinder, and the detection board is located inside the explosion-proof chamber;

[0025] The detection unit is integrated on the detection board;

[0026] The explosion-proof chamber is provided with an explosion-proof gland for the signal line to pass through.

[0027] The present invention also provides a detection method for a material-contact type powder electrostatic monitor, which includes the following steps:

[0028] S1. Conduct the discharge circuit, perform the discharge operation until the first set duration, and then disconnect the discharge circuit;

[0029] S2. Conduct the circuit for measuring interference charges, and disconnect the discharge circuit and the circuit for detecting the total charge;

[0030] S3. Measure the interference charges until the second set duration, then disconnect the circuit for detecting the interference charges, and conduct the circuit for detecting the total charge;

[0031] S4. Measure the total charge until the third set duration to complete one measurement cycle;

[0032] S5. Calculate the corresponding induced charges according to the interference charges, the total charge, the second set duration, and the third set duration.

[0033] Wherein, it further includes step S6, and the induced charges in each measurement cycle are accumulated to the end value of the previous adjacent measurement cycle.

[0034] Compared with the prior art, since the present invention adopts a non-mechanical detection principle, there are no mechanical rotating parts in the whole charge monitoring unit, no cylinders, and no need for a cylinder to drag a constant-volume sampling cylinder to receive and pour materials. The charge monitoring is real-time detection, which can reflect the static charge situation carried by the material in real time. The monitoring response speed has been improved in principle. Due to the absence of cylinders and mechanical sampling cylinders, the service life and reliability of the monitor have been greatly improved.

[0035] The static electricity monitor of the present utility model can be installed at any angle, supporting vertical installation, horizontal installation, and also inclined straight pipe section installation. The static electricity monitor of the present utility model meets the requirement of the pneumatic conveying device design for the static electricity monitor to have flexible installation adaptability, and is suitable for the safety transformation of old powder silos and the pneumatic conveying system with compact pipeline space.

[0036] When the production conditions such as environmental humidity change, the static electricity carried by the material during pneumatic conveying of granular materials changes, resulting in the requirement that the static electricity elimination system needs to continuously measure the static electricity level of the material, adjust the amount of static electricity eliminating ions in real time, and ensure a stable low static electricity amount of the material after static electricity elimination. The static electricity monitor of the present utility model meets this requirement and continuously tracks the change of the static electricity of the material. It can avoid the deficiencies of the past mechanical constant volume using the cylinder sampling method, such as long sampling period, discontinuous sampling, having a data-free area in the middle of sampling, poor tracking of the charge change of the material, the static electricity elimination being based on empirical values, poor convergence, and high residual static electricity charge.

[0037] The static electricity monitor of the present utility model supports direct contact with the material, that is, it supports dilute-phase pneumatic conveying of powder and dense-phase pneumatic conveying of powder, and is suitable for the production of petrochemical powders with a wide range of high volume resistivity. Since this monitor cooperates with an ion wind static eliminator and uses a feedback control algorithm, it can obtain an extremely low residual charge, less than the critical value at which the material does not generate static electricity discharge, improving the safety level of petrochemical powder silos.

[0038] The contact-type continuous detection static electricity monitor of the present utility model shows obvious advantages compared with the traditional cylinder-type sampling static electricity monitor. Its advanced monitoring technology can replace traditional cylinder sampling products, completely solving problems such as intermittent measurement of the material charge by cylinder sampling products, non-intelligent static electricity elimination operation, inconvenient operation, lag in feedback control, and unsatisfactory static electricity elimination effect, and having significant social benefits. Description of the Drawings

[0039] Figure 1 It is a schematic structural diagram of the material contact type powder static electricity monitor proposed by the present utility model.

[0040] Figure 2 It is a schematic circuit structure diagram of the detection unit proposed by the present utility model.

[0041] Figure 3 It is a schematic diagram of the division of the detection period T in the present utility model.

[0042] Figure 4 It is a schematic diagram of the calculation steps of the induced charge.

[0043] Description of the Reference Numerals:

[0044] 1 - Faraday cylinder, 2 - detection unit, 3 - outer cylinder, 4 - explosion-proof chamber, 5 - detection plate;

[0045] 21 - Operational amplifier, 22 - Discharge branch, 23 - First detection branch, 24 - Second detection branch,

[0046] 25 - Wire, 26 - Safety resistor;

[0047] 221 - Discharge switch, 222 - Discharge resistor;

[0048] 231 - First detection switch, 232 - Detection resistor;

[0049] 241 - Second detection switch, 242 - Detection capacitor;

[0050] 41 - Explosion - proof gland. Specific embodiments

[0051] The embodiments described below by referring to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0052] In the prior art, the main problem existing in the contact - type powder electrostatic monitor is that when the material powder contacts the inner wall of the Faraday cylinder 1, due to the direct contact between the material and the inner cylinder of the monitor, collisions and frictions can occur. The pneumatic conveying system usually uses a 304SS stainless - steel pipeline. The inner cylinder of the monitor of the present invention uses a metal pipeline with the same material, the same pipe diameter, and the same internal treatment requirements as the pneumatic conveying. When the material carrying static charges collides with the inner cylinder of the simulated Faraday cylinder of the monitor, it may directly transfer the charges carried by the powder itself to the inner Faraday cylinder at the contact surface. This part of the transferred charges can be defined as Q 转 . When the material powder contacts and separates from the inner Faraday cylinder, due to the different abilities of the powder and the metal inner cylinder to acquire electrons, an unbalanced distribution of charges will occur, and the metal inner cylinder will lose or gain some charges. This part of the charges can be defined as Q 分 . At the same time, due to the principle of the Faraday cylinder, the inner Faraday cylinder will induce opposite static charges of the material inside the inner cylinder, and the detection capacitor outside the Faraday cylinder will have the same amount of opposite - polarity remaining charges. The remaining charges on this part of the external capacitor can be called Q 感 . Due to the co - existence and mixing of Q 转 , Q 分 and Q 感 , if the material directly contacts the inner wall of the simulated Faraday cylinder, the voltage signal on the external capacitor cannot be directly used for charge calculation. This is the reason why the Faraday cover and the traditional simulated Faraday cylinder for detecting continuous material flow must limit the material from contacting the inner cylinder of the Faraday cylinder.

[0053] In the present invention, the following embodiments are proposed to solve the problem.

[0054] Embodiment 1

[0055] Please refer toFigure 1 and Figure 2 , this embodiment proposes a material-contact type powder electrostatic monitor, which includes a Faraday cylinder 1 and a detection unit 2. Specifically, the role of the Faraday cylinder 1 is to generate induced charges with the charges carried by the material powder, and the static electricity of the material is reflected by calculating the amount of induced charges generated by the Faraday cylinder 1.

[0056] In specific implementation, the detection unit 2 is electrically connected to the outer wall of the Faraday cylinder 1; the detection unit 2 is used to detect the charges on the outer wall of the Faraday cylinder 1. According to the different states of the detection unit 2, different types of charge amounts are detected to calculate the corresponding induced charge amounts.

[0057] Specifically, the detection unit 2 is used to sequentially perform a discharge operation, measure interference charges, and measure the total charge of the Faraday cylinder 1 during the detection period. Please refer to Figure 3 , each detection period is a detection cycle. Within the detection cycle, starting from the beginning of the detection cycle, it is sequentially divided into a discharge period T c1 , a first measurement period T c2 and a second measurement period.

[0058] Calculate the induced charge of the Faraday cylinder 1 based on the interference charge, the measurement time of the interference charge, the total charge, and the measurement time of the total charge.

[0059] The interference charge mainly includes transfer charge Q 转 and separation charge Q 分 , the input of the detection unit is the electrical signal input from the Faraday cylinder 1, and its voltage is denoted as V i .

[0060] Specifically, the detection unit 2 includes an operational amplifier 21, a discharge branch 22, a first detection branch 23, and a second detection branch 24; the main role of the discharge branch 22 is to perform a discharge operation, so as to discharge the detection capacitor 242 on the second detection branch 24, so that the interference charge can be sampled during the first detection period T c2 .

[0061] The positive input terminal of the operational amplifier 21 is electrically connected to the outer wall of the Faraday cylinder 1, and the negative input terminal of the operational amplifier 21 is electrically connected to its output terminal.

[0062] One end of the discharge branch 22 is electrically connected to the wire 25, and the other end is grounded; the discharge branch 22 is only turned on during the discharge period and is disconnected at other times.

[0063] One end of the first detection branch 23 is electrically connected to the wire 25, and the other end is grounded; the first detection branch 23 is only closed during the first detection period and is disconnected at other times.

[0064] One end of the second detection branch 24 is electrically connected to the wire 25, and the other end is grounded. The second detection branch 24 is only disconnected during the first detection period and is closed during other periods.

[0065] During specific implementation, it further includes a safety resistor 26. One end of the safety resistor 26 is electrically connected to the wire 25, and the other end is grounded. The safety resistor is Rsaf in Figure 2 . The setting of the safety resistor Rsaf is to ensure that the impedance limit from the Faraday inner cylinder to the protective ground for continuous detection complies with the general standard for preventing electrostatic accidents. Usually, a resistance range of 50M to 500M ohms is taken. For example, a typical value of 500M ohms is taken. Rsaf should not be set too small because Rsaf determines the attenuation rate of the induced signal Qind. Quantitatively detecting Qind is the core purpose of the monitor's detection.

[0066] Specifically, the first detection branch 23 is composed of a first detection switch 231 and a detection resistor 232 connected in series; the first detection switch 231 is a normally open switch and is used to close when measuring interfering charges. Specifically, the first detection switch 231 is a normally open switch Srem and only operates briefly during the T c2 period. The detection resistor Rrem usually takes a value of 500 to 50k ohms, and a typical value of 50k ohms. The resistance of the detection resistor Rrem should not be too large because the purpose of setting the detection resistor Rrem requires the induced charge Qind of the detection inner cylinder to be quickly attenuated.

[0067] During specific implementation, for the convenience of discharging and measuring the total charge amount, this embodiment is further improved. Specifically, the discharge branch 22 is composed of a discharge switch 221 and a discharge resistor 222 connected in series; among them, the discharge resistor Rclo takes a value of 5 to 50Ω, and a typical value of 50Ω is taken. The discharge switch is a numerically controlled normally open switch Sc lo.

[0068] The second detection branch 24 is composed of a second detection switch 241 and a detection capacitor 242 connected in series; the second detection switch 241 is a normally closed switch and is disconnected when detecting interfering charges. The detection capacitor C1 usually takes a value of 1μF to 50μF, and a typical value of 10μF is taken. The second detection switch 241 is a normally closed switch Srem’, and the normally open switch Srem and the normally closed switch Srem’ are controlled by the same signal.

[0069] The numerically controlled normally open switch Sc l o is periodically and briefly closed at the start of each detection separation period T. The short period during which the normally open switch Sc l o is closed is Tc1. Example: For a typical detection separation period T of 1 s, a typical value of C1 of 10 uF, and Rsaf = 500 MΩ, the numerically controlled normally open switch Sc l o is briefly closed at the start of each detection separation period T for a typical value of 4 ms. The closing time accounts for less than 0.5% of the detection separation period; the closing time of the numerically controlled normally open switch Sc l o is greater than 7 times the typical value of the Rc l o, C1 time constant of 0.5 ms, the charge on C1 is discharged, and the remaining charge is less than 0.1% of the original charge amount. After the short period Tc1, the normally open switch Sc l o is opened, and the normally open switch Srem is controlled to be closed for a short period, typically 4 ms. The short period during which the switch Srem is closed is called Tc2. During the short period Tc2, Q 感 has been attenuated, and at the same time, the normally closed switch Srem’ is opened, disconnecting the signal path to C1, and C1 remains in a discharged state. Since the powder material continuously collides with and separates from the inner cylinder of the monitor, the detection inner cylinder 4 transfers charge Q 转 and the separated charge Q 分 of the detection inner cylinder 4 will be continuously generated and detected by Vrem. Q 转 The sum of Q 分 can be calculated from the current flowing through Rrem and time, that is, the voltage across Rrem, the resistance value of Rrem, and time. After the short period Tc2, the normally open switch Srem is opened, and the normally closed switch Srem’ is closed until the end of the detection separation period T. The detection separation period T is continuously repeated periodically.

[0070] During the process of measuring the interfering charge, the calculation formula for the interfering charge is:

[0071]

[0072] where V rem is the voltage across the detection resistor 232 during the process of measuring the interfering charge, R rem is the resistance value of the detection resistor 232, and t is the detection duration of the interfering charge.

[0073] Since the method of sampling during the short period Tc2 is used to obtain Q 转 and Q 分 , this method defaults that within one detection period T, Q 转 and Q 分 are basically unchanged. Therefore, the interfering charge within the second detection period can be calculated.

[0074] In specific implementation, to prevent interference from external signals, an outer cylinder 3 is further included. The outer cylinder 3 is sleeved on the outer periphery of the Faraday cylinder and is insulated from the Faraday cylinder 1; the outer cylinder 3 is grounded. In this way, the outer cylinder 3 is used to form a shielding layer to isolate the interference of external signals.

[0075] The outer cylinder 3 and the Faraday cylinder 1 are separated by an insulating ring. Specifically, two insulating rings can be arranged at both ends of the Faraday cylinder 1. At the same time, a compression ring is used to compress the insulating ring to fix the outer cylinder 3 and the Faraday cylinder 1. In specific implementation, flanges are connected to both ends of the outer cylinder 3, and it can be directly connected in series to the pipeline for material transportation. This monitor can be arranged horizontally, vertically or obliquely.

[0076] In one implementation, to improve safety, an explosion-proof chamber 4 and a detection board 5 are further included; the explosion-proof chamber 4 is located on the outer periphery of the outer cylinder 3, and the detection board 5 is located inside the explosion-proof chamber 4; the detection unit 2 is integrated on the detection board 5; an explosion-proof gland 41 for signal wires to pass through is provided on the explosion-proof chamber 4.

[0077] Since Vi is periodically and briefly grounded during the detected separation period, the final Q 感 is the calculated value during the detected separation period plus the end value of the previous detected separation period. During the short periods of Tc1 and Tc2, the Q 感 signal is lost, and by default, the end value of the previous detected separation period is taken. Therefore, the values of Tc1 and Tc2 should not be too large. Under typical values, Tc1 is taken as 4 ms and Tc2 is taken as 4 ms, and the short period of Tc1 + Tc2 accounts for less than 1% of the detected separation period time. The same as the requirements of the traditional analog Faraday cylinder, when there is no material and no output ions in the Faraday cylinder, that is, in the material transportation pipeline, the detected value Q 感 needs to be zero-calibrated.

[0078] Please refer to Figure 4 for the figure showing the calculation steps, which lists the calculation step principle of Q 转 and Q 分 when they are stable values. TI, TII, and TIII are the detected separation periods. The time ratio is only for illustrative purposes and is not drawn strictly according to typical values. At the same time, for this utility model, Q 感 and Q 转 allow small fluctuations. 分

[0079] Q 总 minus the transferred charge Q 转 in the Faraday cylinder 1 and the separated charge Q 分 to obtain the induced charge Q 感 of the detected inner cylinder, and the transferred charge Q 转 and the separated charge Q 分 ​It is obtained by detecting the short time period Tc2 in the separated time period T and sampling by the time segmentation method. This kind of material-contact type using the single analog Faraday inner cylinder electrostatic continuous detection method is called the time-division differential analog Faraday cylinder electrostatic continuous detection method.

[0080] Embodiment 2

[0081] This embodiment is a method proposed on the basis of Embodiment 1, and the same parts will not be repeated.

[0082] This embodiment proposes a detection method for the material-contact type powder electrostatic monitor described in Embodiment 1, which includes the following steps:

[0083] S1, Turn on the discharge circuit, perform the discharge operation until the first set duration, and then turn off the discharge circuit; the on / off of the discharge circuit is controlled by the on / off of the discharge switch. The first set duration is Tc1, and its value can refer to Embodiment 1.

[0084] S2, Turn on the circuit for measuring interference charges, and turn off the discharge circuit and the circuit for detecting the total charge amount. That is, the discharge switch is off, the first detection switch is on, and the second detection switch is off.

[0085] S3, Measure the interference charges until the second set duration, then turn off the circuit for detecting the interference charges, and turn on the circuit for detecting the total charge amount. Specifically, the second set duration is the duration of the first detection period. The calculation method of the interference charges can refer to Embodiment 1 and will not be repeated here.

[0086] S4, Measure the total charge amount until the third set duration to complete a measurement cycle. The total charge amount is calculated using the polar time integration method.

[0087] S5, Calculate the corresponding induced charges according to the interference charges, the total charge amount, the second set duration, and the third set duration.

[0088] S6, Accumulate the induced charges in each measurement cycle to the end value of the previous adjacent measurement cycle. In this way, the measurement results can be made continuous.

[0089] The structure, features and effects of the present invention have been described in detail based on the embodiments shown in the drawings above. The above is only the preferred embodiment of the present invention, but the present invention is not limited to the scope shown in the drawings. Any changes made according to the concept of the present invention, or modified into equivalent embodiments with equivalent changes, still within the spirit covered by the specification and the drawings, should be within the protection scope of the present invention.

Claims

1. A material-contact type powder electrostatic monitor, characterized in that: It includes a Faraday cylinder (1) and a detection unit (2); The detection unit (2) is electrically connected to the outer wall of the Faraday cylinder (1); The detection unit (2) is used to sequentially perform a discharge operation, measure interfering charges, and measure the total charge of the Faraday cylinder (1) during a detection period; Calculate the induced charge of the Faraday cylinder (1) based on the interfering charges, the measurement time of the interfering charges, the total charge, and the measurement time of the total charge.

2. The material contact type powder electrostatic monitor according to claim 1, characterized in that: The detection unit (2) includes an operational amplifier (21), a discharge branch (22), a first detection branch (23), and a second detection branch (24); The non-inverting input terminal of the operational amplifier (21) is electrically connected to the outer wall of the Faraday cylinder (1), and the inverting input terminal of the operational amplifier (21) is electrically connected to its output terminal; One end of the discharge branch (22) is electrically connected to the wire (25), and the other end is grounded; One end of the first detection branch (23) is electrically connected to the wire (25), and the other end is grounded; One end of the second detection branch (24) is electrically connected to the wire (25), and the other end is grounded.

3. The material-contact type powder electrostatic monitor according to claim 2, wherein: The first detection branch (23) is composed of a first detection switch (231) and a detection resistor (232) connected in series; the first detection switch (231) is a normally open switch and is used to close when measuring interfering charges.

4. The material-contact type powder electrostatic monitor according to claim 3, wherein: The discharge branch (22) is composed of a discharge switch (221) and a discharge resistor (222) connected in series; The second detection branch (24) is composed of a second detection switch (241) and a detection capacitor (242) connected in series; the second detection switch (241) is a normally closed switch and is opened when detecting interfering charges.

5. The material-contact type powder electrostatic monitor according to claim 4, characterized in that: When the discharge operation is completed, the remaining charge amount of the detection capacitor (242) is not greater than 0.1% of the original charge amount.

6. The powder electrostatic monitor of the material contact type according to claim 3, characterized in that: During the process of measuring interfering charges, the calculation formula for interfering charges is: Among them, V rem is the voltage across the detection resistor (232) during the measurement of the interfering charge, and R rem is the resistance value of the detection resistor (232), and t is the detection duration of the interfering charge.

7. The powder electrostatic monitor of the material contact type according to any one of claims 1-6, characterized in that: It further includes an outer cylinder (3), the outer cylinder (3) is sleeved on the outer periphery of the Faraday cylinder, and is insulated from the Faraday cylinder (1); the outer cylinder (3) is grounded.

8. The material-contact type powder electrostatic monitor according to claim 7, characterized in that: It further includes an explosion-proof chamber (4) and a detection board (5); The explosion-proof chamber (4) is located on the outer periphery of the outer cylinder (3), and the detection board (5) is located inside the explosion-proof chamber (4); The detection unit (2) is integrated on the detection board (5); The explosion-proof chamber (4) is provided with an explosion-proof gland (41) for the signal wire to pass through.

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