A mine-used electric method monitoring field source emission device with intelligent variable access resistance

Abstract

The application discloses a mine electric method monitoring field source emission device and method with intelligent variable access resistance, which comprises an embedded central control module, a stepping motor driver, a stepping motor, a disc adjustable sliding rheostat, an electric method field source signal emission module, a switch matrix module, a MOSFET switch, a sampling resistor and a monitoring electrode group; the embedded central control module is connected with the stepping motor driver, the electric method field source signal emission module, the switch matrix module, the MOSFET switch and the sampling resistor respectively; the stepping motor driver, the stepping motor and the disc adjustable sliding rheostat are sequentially connected; the switch matrix module is connected with the electric method field source signal emission module; and the sampling resistor, the MOSFET switch, the switch matrix module, the disc adjustable sliding rheostat and the monitoring electrode group are sequentially connected in a head-to-tail mode to form an emission loop. The application can automatically adjust the access resistance in the emission loop, so that the emission current is always stably below the intrinsic safety current limiting value.

Description

Technical Field

[0001] This invention belongs to the field of geophysical exploration and monitoring technology, and relates to a mine electrical monitoring field source emission device with intelligent variable access resistance. Background Technology

[0002] Electrical resistivity monitoring technology is widely used in monitoring coal seam mining damage and water hazards due to its sensitivity to changes in coal and rock resistivity. In underground coal mines, high-power electrical field source signals are required to obtain reliable monitoring data. However, in the unique and hazardous environment of underground coal mines, filled with explosive gases, the power of the electrical field source is strictly limited. The transmitted field source signal must meet intrinsic safety requirements to ensure that even in the event of a short circuit or other fault in the transmission circuit, the released energy is insufficient to ignite the explosive gas.

[0003] Currently, to meet intrinsic safety requirements, the common technical method is to set the field source transmitter to high-voltage, constant-voltage transmission. After the transmitter output is activated, the current value of the transmitter circuit is detected. When the detected current value exceeds the intrinsically safe current limit, the transmitter circuit is cut off through a comparison circuit and a switching circuit. However, during electrical resistivity tomography (EPM) monitoring, the field source signal needs to be switched between all monitoring electrodes. Furthermore, due to the long monitoring cycle, the grounding resistance between different field source transmitter electrodes varies significantly and changes over time. To ensure the transmitter circuit functions properly, existing technology connects a large, fixed-value access resistor between the transmitter output and the transmitter electrode, based on pre-mining testing, to keep the current value of the transmitter circuit consistently below the intrinsically safe current limit. This fixed-value access resistor method is highly susceptible to operator subjectivity and cannot be flexibly adjusted automatically according to changes in ground resistance between different transmitter electrodes. Consequently, it fails to fully utilize the maximum power output under intrinsically safe limits, resulting in the monitoring field source energy not being maximized to the target geological body to obtain the best possible field source response signal. This affects data acquisition quality and, consequently, the accuracy of inversion interpretation. Summary of the Invention

[0004] The purpose of this invention is to provide a mine-use electrical monitoring field source emission device with intelligent variable access resistance, in order to solve the problem that the existing technology cannot flexibly adjust automatically according to the changes in earth resistance between different emission electrodes, resulting in low accuracy of inversion interpretation.

[0005] To achieve the above objectives, on the one hand, the present invention provides a mine-use electrical field source transmitting device with intelligent variable access resistance, comprising an embedded central control module, a stepper motor driver, a stepper motor, a disc-adjustable sliding rheostat, an electrical field source signal transmitting module, a switch matrix module, a MOSFET switch, a sampling resistor, and a monitoring electrode group; wherein, the embedded central control module is connected to the stepper motor driver, the electrical field source signal transmitting module, the switch matrix module, the MOSFET switch, and the sampling resistor respectively; the stepper motor driver, the stepper motor, and the disc-adjustable sliding rheostat are connected in sequence; the switch matrix module is connected to the electrical field source signal transmitting module; the sampling resistor, the MOSFET switch, the switch matrix module, the disc-adjustable sliding rheostat, and the monitoring electrode group are connected end to end in sequence to form a transmitting circuit.

[0006] Furthermore, the electrical field source signal transmitting module includes a boost DC-DC module, a signal isolator, and a full-bridge converter circuit; wherein, the boost DC-DC module and the signal isolator are respectively connected to the full-bridge converter circuit, and the signal isolator is connected to the embedded central control module; the output terminals A and B of the full-bridge converter circuit are connected to a pair of electrodes in the monitoring electrode group selected by the switch matrix module.

[0007] Furthermore, the boost DC-DC module is an HZD10C-07S100 DC-DC converter, the signal isolator is a MAX22517 dual-channel digital isolator, and the full-bridge conversion circuit is an MTI85W100GC three-phase full-bridge converter.

[0008] Furthermore, the switch matrix module is a 32x4 medium-density matrix switch module.

[0009] Furthermore, the monitoring electrode group includes 32 monitoring electrodes.

[0010] On the other hand, the present invention also discloses a method for monitoring field sources in mines using electrical resistivity methods, employing the intelligent variable access resistor field source emission device for monitoring mines described above, specifically including the following steps:

[0011] Step 1: Set the adjustable sliding rheostat to its initial state;

[0012] Step 2: Set the voltage value U of the field source transmission signal. s and intrinsically safe current limiting value I lim Step 3: Set the waveform and frequency of the field source emission signal according to the needs of electrical monitoring;

[0013] Step 4: The embedded central control module generates corresponding control signals to control the switch matrix module to select a pair of electrodes in the monitoring electrode group, and connects them to the two output terminals of the electric field source signal transmitting module as the two transmitting electrodes of the field source signal;

[0014] Step 5: The electrical field source signal transmission module activates the two transmitting electrodes to transmit the field source signal based on the control signal generated by the embedded central control module; the other electrodes in the monitoring electrode group acquire electrical signal data.

[0015] Step Six: The embedded central control module acquires the voltage across the sampling resistor, calculates the voltage value Ur across the sampling resistor through signal amplification, and calculates the transmission current value in the transmission circuit based on the voltage value Ur. I, The unit is V, and the unit of 10 is , The unit is A;

[0016] Step 7: The embedded central control module transmits the current value I. r Compared with the intrinsically safe current limit value I set in step two lim Comparison, if the emission current value I r Less than the intrinsically safe current limit value I lim The embedded central control module then sends a PWM pulse control signal to the stepper motor driver. The stepper motor driver controls the stepper motor according to the received signal. The stepper motor drives the cantilever of the adjustable sliding rheostat to rotate counterclockwise, reducing the input resistance R in the transmitting circuit. t If the emission current value I r Not less than the intrinsically safe current limit value I lim Then proceed to step ten;

[0017] Step 8: Return to Step 6 to form a negative feedback control logic until the transmit current value I in the transmitting circuit is reached. r Approximately equal to the intrinsically safe current limiting value I lim Proceed to step nine;

[0018] Step 9: When data acquisition is complete, the embedded central control module controls the electrical field source signal transmission module to stop the transmission of field source signals from the current two transmitting electrodes. At the same time, the embedded central control module generates a corresponding control signal to control the switch matrix module to select another pair of electrodes in the monitoring electrode group as the two transmitting electrodes of the field source signal and mark them. Then return to step 5 until all electrodes in the monitoring electrode group have been marked, and the transmission process ends.

[0019] Step 10: The embedded central control module sends a control logic signal to the MOSFET switch, causing the gate control signal of the MOSFET switch to go low, disconnecting the drain and source, thus cutting off the emitter circuit. Then, the embedded central control module sends a PWM pulse control signal to the stepper motor driver, controlling the cantilever of the adjustable sliding rheostat of the stepper motor drive disk to rotate clockwise, increasing the input resistance R in the emitter circuit. tUntil the transmitting current value I in the transmitting circuit r Approximately equal to the intrinsically safe current limiting value I lim Return to step nine.

[0020] Furthermore, the characteristic is that, in step two, U s =100V,I lim =60mA.

[0021] Furthermore, in step six, the transmit current value in the transmit circuit is:

[0022] I

[0023] in, The voltage across the sampling resistor is expressed in volts (V); the unit for 10 is... ; This is the emission current value, in amperes (A).

[0024] The beneficial effects of this invention patent are:

[0025] 1. During the electrical monitoring process, the microcontroller in this invention calculates the current between the field source emitting electrodes through the sampling resistor, executes the PID feedback algorithm, controls the rotation angle of the stepping electrode, and then adjusts the resistance value of the input resistor between the emitting circuit so that it continuously approaches the set intrinsically safe current limit value.

[0026] 2. When switching the field source emission electrode during the electrical monitoring process, the present invention can automatically adjust the connection resistance between different emission electrodes so that the emission current between different electrodes is always stable below the intrinsically safe current limit value;

[0027] 3. During long-term electrical current monitoring, the emission current between the emitting electrodes is not affected by changes in time and the environment in which the electrodes are located, so that the emission current remains stable at a value close to the intrinsically safe current limit.

[0028] 4. This invention makes full use of the maximum field source transmission power under intrinsically safe conditions in order to obtain reliable received data, thereby obtaining credible inversion interpretation results and reducing the occurrence of water-related accidents;

[0029] 5. This device can disconnect the MOSFET switch when the inter-loop current exceeds the set intrinsically safe current limit, thus disconnecting the transmitting circuit. Therefore, the MOSFET switch can function as a primary intrinsically safe protection circuit. The variable connection resistor in this device is initially at its maximum resistance value, limiting the transmitting circuit current to not exceed the intrinsically safe current value. This variable connection resistor can function as another level of intrinsically safe protection circuit. When any of the above intrinsically safe protection currents is used as a fault counting point (i.e., device failure), it will not cause ignition during the spark ignition test. Therefore, this device has a two-stage intrinsically safe protection circuit, and its principle meets the requirements of intrinsically safe circuits for "ib" level electrical equipment. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the intelligent variable access resistor for mine electrical monitoring field source emission device of the present invention;

[0031] Figure 2 This is a schematic diagram of the electrical field source signal transmission module.

[0032] Figure 3 This is the electrical schematic diagram of the signal transmitting module of the electric field source.

[0033] Figure 4 This is a logic diagram of the switch matrix module;

[0034] In the diagram, 1-embedded central control module; 2-stepper motor driver; 3-stepper motor; 4-disc adjustable sliding rheostat; 5-electric field source signal transmission module; 6-switch matrix module; 7-MOSFET switch; 8-sampling resistor; 9-monitoring electrode group; 10-boost DC-DC module; 11-signal isolator; 12-full bridge converter circuit. Detailed Implementation

[0035] The following will describe in detail the implementation of this application with reference to the accompanying drawings and embodiments, so that the implementation process of how this application uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0036] Please refer to Figure 1 The present invention provides a mine-use electrical field source transmitting device with intelligent variable access resistor, comprising an embedded central control module 1, a stepper motor driver 2, a stepper motor 3, a disc-mounted adjustable sliding rheostat 4, an electrical field source signal transmitting module 5, a switch matrix module 6, a MOSFET switch 7, a sampling resistor 8, and a monitoring electrode group 9. The embedded central control module 1 is connected to the stepper motor driver 2, the electrical field source signal transmitting module 5, the switch matrix module 6, the MOSFET switch 7, and the sampling resistor 8. The stepper motor driver 2, the stepper motor 3, and the disc-mounted adjustable sliding rheostat 4 are connected sequentially. The switch matrix module 6 is connected to the electrical field source signal transmitting module 5. The sampling resistor 8, the MOSFET switch 7, the switch matrix module 6, the disc-mounted adjustable sliding rheostat 4, and the monitoring electrode group 9 are connected end-to-end to form a transmitting circuit.

[0037] The embedded central control module 1, optionally the EMB8610I embedded industrial control module produced by Beijing Zhongqian Lingyun Co., Ltd., is used to acquire the voltage value of the sampling resistor 8, and then calculate the current between a pair of electrodes in the monitoring electrode group 9 that serves as the electric field source for emission as the emission current value; it is used to set the intrinsically safe current limit value, and execute the PID feedback algorithm to continuously compare the emission current value with the intrinsically safe current limit value. Based on the comparison result, it generates the PWM pulse control signal and forward and reverse direction signal required by the stepper motor driver 2, drives the stepper motor 3 to adjust the resistance value of the adjustable sliding rheostat 4 to change the connection resistance value between the emission circuits; it is used to generate the control logic signals required by the electric field source signal emission module 5, the switch matrix module 6, and the MOSFET switch 7 respectively.

[0038] Stepper motor driver 2 is used to convert the PWM pulse control signal sent by the embedded central control module 1 into a strong current signal required by the stepper motor 3, thereby driving the stepper motor 3 to rotate; it is also used to receive the forward and reverse direction signals sent by the embedded central control module 1. The forward rotation signal is high level, and the reverse rotation signal is low level. When the signal is high level, the stepper motor 3 is controlled to have its A terminal connected to VCC and its B terminal grounded, thus rotating forward; when the signal is low level, the stepper motor 3 is controlled to have its A terminal grounded and its B terminal connected to VCC, thus rotating in reverse.

[0039] Stepper motor 3 is the actuator of stepper motor driver 2, used to drive the cantilever of the adjustable sliding rheostat 4 to rotate under the drive of stepper motor driver 2.

[0040] The adjustable sliding rheostat 4 is the actuator of the stepper motor 3. It changes its own resistance value by rotating the cantilever, which serves as the input resistance in the transmitting circuit. Considering the apparent resistivity of the coal seam, the source voltage of the transmitting field, the current limiting value, and the requirement that the working power of the intrinsically safe device does not exceed 2 / 3 of its rated power, the resistance range of the adjustable sliding rheostat 4 is R=1Ω-2000Ω, and the power P is not less than 15W.

[0041] The electric field source signal transmitting module 5 receives the control logic signals sent by the embedded central control module 1 and converts the control logic signals into high-voltage square wave field source output signals with positive and negative voltages relative to ground. Its composition is as follows: Figure 2 As shown, it includes a boost DC-DC module 10, a signal isolator 11, and a full-bridge converter circuit 12; wherein, the boost DC-DC module 10 and the signal isolator 11 are respectively connected to the full-bridge converter circuit 12, and the signal isolator 11 is connected to the embedded central control module 1; the output terminals A and B of the full-bridge converter circuit 12 are used to connect to a pair of electrodes in the monitoring electrode group 9 selected by the switch matrix module 6, which are the transmitting electrodes A and B of the electric field source transmitting signal.

[0042] The boost DC-DC module 10 is an HZD10C-07S100 DC-DC converter manufactured by Beijing Huizhong Power Technology Co., Ltd., which converts a 4V-10V DC input to a maximum 100V / 100mA DC output. The signal isolator 11 is a MAX22517 dual-channel digital isolator manufactured by Maxim Integrated, used to isolate the control logic signals F1 and F2 generated by the embedded central control module 1 from the control logic signals of the full-bridge converter circuit 12. The full-bridge converter circuit 12 is an MTI85W100GC three-phase full-bridge converter manufactured by IXYS, which, through its four internal MOSFETs under the control logic signals, converts the 100V / 100mA DC output into a 100V / 100mA square wave field source signal output. The specific connection method is as follows... Figure 3 As shown, terminal 1N1F of device P3 (i.e., signal isolator 11) is connected to logic control signal F1 from embedded central control module 1; terminal 2N2F is connected to logic control signal F2 from embedded central control module 1; terminals 3 and 4 are connected to the 3.3V power supply and its ground; terminal 5 is connected to the output ground terminal 5 of DC-DC converter P1; terminal 6 is connected to the input 5V power supply terminal 2 of DC-DC converter; terminal 7 is connected to terminals G2 and G3 of device P2 (i.e., full-bridge converter circuit 12); and terminal 8 is connected to terminals G1 and G4 of device P2. Terminals S1, S2, S3, and S4 of device P2 are connected to the output ground terminal 5 of device P1 (i.e., boost DC-DC module 10); terminal L+ is connected to terminal 4 of device P1; terminal L- is connected to terminal 5 of device P1; terminal L1 is output terminal A; and terminal L2 is output terminal B. Terminal 3 of device P1 is an empty terminal and is not connected to any circuit. In the above technical solution, the control logic signals F1 and F2 from the embedded central control module 1 are square wave signals that are opposite to each other. When F1 is high and F2 is low, the current direction of the DC-DC high voltage output is from output terminal A to output terminal B; when F1 is low and F2 is high, the current direction of the DC-DC high voltage output is from output terminal B to output terminal A. In this way, the control logic signal can be converted into AC high voltage square wave field source output signal on the transmitting electrode A and transmitting electrode B.

[0043] Switch matrix module 6, optional Figure 4 The 32x4 medium-density matrix switch module manufactured by Pickering shown can realize any 32-to-4 logic switch. It is used to select the corresponding connection of two monitoring electrodes in monitoring electrode group 9 according to the control logic signal generated by the embedded central control module 1. Figure 2 The output terminals A and B shown are used as the selected monitoring electrode to form the transmission channel.

[0044] The MOSFET switch 7, which is an N-channel field-effect transistor, is used to cut off the transmission circuit in special circumstances such as the failure of the disk-adjustable sliding rheostat 4, based on the control logic signal generated by the embedded central control module 1, i.e., the MOSFET gate control signal, thereby ensuring the intrinsic safety of the device of the present invention.

[0045] The sampling resistor 8 is a 10-ohm, 1% non-inductive precision resistor used to convert the current value in the transmission circuit into a voltage value for the embedded central control module 1 to acquire.

[0046] The monitoring electrode group 9 includes multiple monitoring electrodes (32 monitoring electrodes numbered 1# to 32# in this embodiment), which are generally made of copper rods or stainless steel. All electrodes are buried in the coal seam floor, and any two electrodes can be arbitrarily selected as monitoring emission source electrodes through the switch matrix module 6.

[0047] The method of the present invention uses the above-described launching device and specifically includes the following execution steps:

[0048] Step 1: Set the adjustable sliding rheostat 4 to its initial state (maximum resistance) to ensure the current in the transmitting circuit is at its minimum possible value.

[0049] Step 2: Set the voltage value U of the field source transmission signal. s and intrinsically safe current limiting value I lim To more clearly describe the execution process of this invention, a typical value U of the intrinsically safe field source emission signal in electrical monitoring is used. s =100V, I lim For example, 60mA;

[0050] Step 3: Set the waveform and frequency of the field source emission signal according to the needs of electrical resistivity monitoring;

[0051] Step 4: The embedded central control module 1 generates a corresponding control signal to control the switch matrix module 6 to select a pair of electrodes in the monitoring electrode group 9, and connects the output terminals A and B of the electric field source signal transmitting module 5 as the two transmitting electrodes of the field source signal (i.e., transmitting electrode A and transmitting electrode B).

[0052] Step 5: The electrical field source signal transmitting module 5 activates the two transmitting electrodes to transmit the field source signal according to the control signal generated by the embedded central control module 1; the other electrodes in the monitoring electrode group collect electrical signal data.

[0053] Step Six: The embedded central control module 1 acquires the voltage across the sampling resistor 8, calculates the voltage value Ur across the sampling resistor 8 through signal amplification, and calculates the transmission current value in the transmission circuit based on the voltage value Ur. I, The unit is V, and the unit of 10 is , The unit is A;

[0054] Step 7: Embedded central control module 1 transmits the current value I. r Compared with the intrinsically safe current limit value I set in step two lim Comparison, if the emission current value I r Less than the intrinsically safe current limit value I lim The embedded central control module 1 sends a PWM pulse control signal to the stepper motor driver 2. The stepper motor driver 2 controls the stepper motor 3 according to the received signal. The stepper motor 3 drives the cantilever of the adjustable sliding rheostat 4 to rotate counterclockwise, reducing the input resistance R in the transmitting circuit. t If the emission current value I r Not less than the intrinsically safe current limit value I lim Then proceed to step ten;

[0055] Step 8: Return to Step 6 to form a negative feedback control logic until the transmit current value I in the transmitting circuit is reached. r Approximately equal to the intrinsically safe current limiting value I lim Proceed to step nine;

[0056] Step 9: When data acquisition is complete, the embedded central control module 1 controls the electrical field source signal transmission module 5 to stop the transmission of field source signals from the current two transmitting electrodes. At the same time, the embedded central control module 1 generates a corresponding control signal to control the switch matrix module 6 to select another pair of electrodes in the monitoring electrode group 9 as the two transmitting electrodes of the field source signal and mark them. Then, return to step 5 until all electrodes in the monitoring electrode group 9 have been marked, and the transmission process ends.

[0057] Step 10: The embedded central control module 1 sends a control logic signal to the MOSFET switch 7, causing the gate control signal of the MOSFET switch 7 to go low, disconnecting the drain and source, thus cutting off the emitter circuit. Then, the embedded central control module 1 sends a PWM pulse control signal to the stepper motor driver 2, controlling the stepper motor 3 to drive the cantilever of the adjustable sliding rheostat 4 to rotate clockwise, increasing the connection resistance R in the emitter circuit. t Until the transmitting current value I in the transmitting circuit r Approximately equal to the intrinsically safe current limiting value I lim Return to step nine.

[0058] It is worth noting that in the above technical solution, the MOSFET switch 7 and the disc adjustable sliding rheostat 4 form a double reliable intrinsically safe protection circuit. If a short circuit or other fault occurs in either circuit, it will not affect the intrinsic safety of the transmission output, so that the device meets the general requirements for Class Ib intrinsically safe equipment in GB3836.4-2021.

Claims

1. A mine electrical method monitoring field source transmitter device of intelligent variable access resistance, characterized in that, The system includes an embedded central control module (1), a stepper motor driver (2), a stepper motor (3), a disc-adjustable sliding rheostat (4), an electro-field source signal transmission module (5), a switch matrix module (6), a MOSFET switch (7), a sampling resistor (8), and a monitoring electrode group (9). The embedded central control module (1) is connected to the stepper motor driver (2), the electro-field source signal transmission module (5), the switch matrix module (6), the MOSFET switch (7), and the sampling resistor (8), respectively. The stepper motor driver (2), the stepper motor (3), and the disc-adjustable sliding rheostat (4) are connected in sequence. The switch matrix module (6) is connected to the electro-field source signal transmission module (5). The sampling resistor (8), the MOSFET switch (7), the switch matrix module (6), the disc-adjustable sliding rheostat (4), and the monitoring electrode group (9) are connected end to end in sequence to form a transmission circuit.

2. The intelligent variable access resistance mine electrical monitoring field source transmitting device of claim 1, wherein, The electrical field source signal transmitting module (5) includes a boost DC-DC module (10), a signal isolator (11), and a full-bridge converter (12); wherein the boost DC-DC module (10) and the signal isolator (11) are respectively connected to the full-bridge converter (12), and the signal isolator (11) is connected to the embedded central control module (1); the output terminals A and B of the full-bridge converter (12) are connected to a pair of electrodes in the monitoring electrode group (9) selected by the switch matrix module (6).

3. The intelligent variable access resistance mine electrical monitoring field source transmitting device of claim 2, wherein, The boost DC-DC module (10) is an HZD10C-07S100 DC-DC converter, the signal isolator (11) is a MAX22517 dual-channel digital isolator, and the full-bridge converter circuit (12) is an MTI85W100GC three-phase full-bridge converter.

4. The intelligent variable access resistance mine electrical monitoring field source transmitting device of claim 1, wherein, The switch matrix module (6) is a 32x4 medium-density matrix switch module.

5. The intelligent variable access resistor for mine electrical monitoring field source emission device as described in claim 1, characterized in that, The monitoring electrode group (9) includes 32 monitoring electrodes.

6. A method for transmitting field sources for mine electrical monitoring, employing a mine electrical monitoring field source transmitting device with an intelligent variable access resistor as described in any one of claims 1 to 5, specifically comprising the following steps: Step 1: Place the adjustable sliding rheostat (4) in its initial state; Step two: set the voltage value U of the field source transmitting signal s and the intrinsic safety current limiting value I lim ; Step 3: Set the waveform and frequency of the field source emission signal according to the needs of electrical resistivity monitoring; Step 4: The embedded central control module (1) generates corresponding control signals to control the switch matrix module (6) to select a pair of electrodes in the monitoring electrode group (9) and connect them to the two output terminals of the electric field source signal transmission module (5) as the two transmitting electrodes of the field source signal; Step 5: The electrical field source signal transmission module (5) activates the two transmitting electrodes to transmit the field source signal according to the control signal generated by the embedded central control module (1); and monitors other electrodes in the electrode group to collect electrical signal data. Step 6: The embedded central control module (1) collects the voltage across the sampling resistor (8), calculates the voltage value Ur across the sampling resistor (8) through signal amplification, and calculates the transmission current value in the transmission circuit based on the voltage value Ur. I, The unit is V, and the unit of 10 is , The unit is A; Step 7: Embedded central control module (1) transmits the current value I r Compared with the intrinsically safe current limit value I set in step two lim Comparison, if the emission current value I r Less than the intrinsically safe current limit value I lim Then the embedded central control module (1) sends a PWM pulse control signal to the stepper motor driver (2), and the stepper motor driver (2) controls the stepper motor (3) according to the received signal. The stepper motor (3) drives the cantilever of the adjustable sliding rheostat (4) to rotate counterclockwise, reducing the access resistance R in the transmitting circuit. t If the transmitting current value I r Not less than the intrinsically safe current limit value I lim Then proceed to step ten; Step eight: return to step six until the value of the emission current I in the emission circuit is approximately equal to the intrinsic limiting value I r I lim , step nine is executed; Step 9: When data acquisition is completed, the embedded central control module (1) controls the electric field source signal transmission module (5) to stop the current two transmitting electrodes from transmitting the field source signal. At the same time, the embedded central control module (1) generates a corresponding control signal to control the switch matrix module (6) to select another pair of electrodes in the monitoring electrode group (9) as the two transmitting electrodes of the field source signal and mark them. Then return to step 5 until all electrodes in the monitoring electrode group (9) have been marked and the transmission process ends. Step 10: The embedded central control module (1) sends a control logic signal to the MOSFET switch (7) to make the gate control signal of the MOSFET switch (7) low, disconnecting the drain and source, i.e. cutting off the transmission circuit. Then, the embedded central control module (1) sends a PWM pulse control signal to the stepper motor driver (2) to control the stepper motor (3) to drive the cantilever of the adjustable sliding rheostat (4) to rotate clockwise, increasing the access resistance R in the transmission circuit. t Until the transmitting current value I in the transmitting circuit r Approximately equal to the intrinsically safe current limiting value I lim Return to step nine.

7. A method of field source transmission for mine electrical monitoring as claimed in claim 6, characterised in that, In the second step, U s = 100 V, I lim = 60 mA.

8. A method of field source transmission for mine electrical monitoring as claimed in claim 6 characterised in that, In step six, the transmission current value in the transmission circuit is: I wherein, V is the voltage value on the sampling resistor, in V; 10 is the unit of ; I is the emission current value, in A.

Images