Multi-channel stray current monitoring sensor and sampling method thereof

Abstract

The invention provides a multi-channel stray current monitoring sensor and a sampling method thereof, and relates to the technical field of stray current monitoring equipment. In the sensor, a first front-end sampling circuit, a second front-end sampling circuit, a third front-end sampling circuit and a fourth front-end sampling circuit sample rail-ground voltage, junction-ground voltage, rail-junction voltage and junction ratio voltage respectively and input the rail-ground voltage, the junction-ground voltage, the rail-junction voltage and the junction ratio voltage into four channels of a first analog channel selector in a one-to The steel rail sampling circuit collects two paths of 10m steel rail voltages of parallel steel rails and correspondingly inputs the two paths of 10m steel rail voltages into two channels of the second analog channel selector; the output ends of the first and second analog channel selectors are correspondingly connected to the first and second input ends of the analog-to-digital converter; the output end of the analog-to-digital converter is connected to the processor; the control ends of the first analog channel selector and the second analog channel selector are connected to the processor. The sensor can support stray current corrosion degree analysis and evaluation by collecting six paths of voltage signals, the potential safety hazard degree evaluation accuracy is improved, and the potential safety hazard risk is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of stray current detection equipment, and in particular to a multi-channel stray current monitoring sensor and a sampling method thereof. Background Art

[0002] Urban rail transit mainly uses DC traction power supply. In the DC traction system, the positive pole is connected to the contact network or contact rail, and the running rail is used as the return channel. Since the rails and the roadbed are not completely insulated, part of the current that originally passed through the running rails leaks into the earth, and then flows back to the traction substation through buried metal, pipes, cables, etc. The current leaked into the earth is stray current. If a large amount of leakage occurs, it will seriously corrode buried metal, pipes, cables and other equipment, and at the same time cause abnormal increase in rail potential, threatening the safety of passengers and electrical equipment. In the early days of the subway being built and put into operation, the insulation between the running rails and the roadbed was high, and the rail-to-ground transition resistance was large. As the subway operates for a long time, it is affected by inevitable destructive factors such as pollution and humidity, and the insulation between the running rails and the roadbed decreases, the rail-to-ground transition resistance decreases, and the leakage of stray current increases, causing corrosion to communication cables, water pipes, gas pipelines, structural steel bars, and buried metals in the soil around the subway.

[0003] To assess the actual impact of stray currents on site, traditional stray current monitoring sensors usually monitor and analyze two sets of analog quantities: the voltage of the structural steel bars to the reference electrode and the voltage of the return rail to the structural steel bars. The traditional method has too few data types to support the analysis and assessment of the degree of stray current corrosion, and the accuracy of judging the degree of safety hazards faced by passengers and electrical equipment is low. Summary of the invention

[0004] In order to solve the above technical problems existing in the prior art, realize the graded evaluation of the degree of stray current corrosion, and accurately judge the safety hazards faced by passengers and electrical equipment, the present invention provides a new type of stray current detection sensor.

[0005] Specifically, in a first aspect, the present invention provides a multi-channel stray current monitoring sensor, comprising:

[0006] A front-end sampling module, a rail sampling circuit, a first analog channel selector, a second analog channel selector, an analog-to-digital converter and a processor;

[0007] The front-end sampling module includes a first front-end sampling circuit, a second front-end sampling circuit, a third front-end sampling circuit and a fourth front-end sampling circuit, and is connected to the four channels of the first analog channel selector in a one-to-one correspondence;

[0008] The first front-end sampling circuit samples the rail-to-ground voltage, the second front-end sampling circuit samples the junction-to-ground voltage, the third front-end sampling circuit samples the rail-to-junction voltage, and the fourth front-end sampling circuit samples the junction ratio voltage;

[0009] The rail sampling circuit collects the voltages of two 10m rails at the same position of the parallel rails and inputs them into two channels of the second analog channel selector accordingly;

[0010] The output end of the first analog channel selector is connected to the first input end of the analog-to-digital converter, and the output end of the second analog channel selector is connected to the second input end of the analog-to-digital converter; the output end of the analog-to-digital converter is connected to the processor;

[0011] Control terminals of the first analog channel selector and the second analog channel selector are both connected to the processor.

[0012] Furthermore, it also includes a linear optocoupler isolation circuit;

[0013] The number of the linear optocoupler isolation circuits is 4, and the input end of each linear optocoupler isolation circuit is connected to the output end of a front-end sampling circuit, and the output end is connected to a channel of the first analog channel selector.

[0014] Furthermore, each front-end sampling circuit also includes an RC filtering circuit; in the RC filtering circuit, a TVS device is provided in parallel with a resistor, an input resistor is provided at the input end, and an output end is connected to a channel of the first analog channel selector.

[0015] Furthermore, each front-end sampling circuit also includes an emitter follower; an output end of the emitter follower is connected to a channel of the line first analog channel selector.

[0016] Furthermore, each front-end sampling circuit also includes a first-order reverse active filtering circuit and a subtraction circuit; the output end of the first-order reverse active filtering circuit is connected to a channel of the first analog channel selector via the subtraction circuit.

[0017] Furthermore, each front-end sampling circuit also includes an RC filter circuit, an emitter follower, a first-order reverse active filter circuit and a subtraction circuit connected in series in sequence; in the RC filter circuit, a TVS device is provided in parallel with a resistor, and an input resistor is provided at the input end; the output end of the subtraction circuit is connected to a channel of the first analog channel selector.

[0018] Furthermore, it also includes a linear optocoupler isolation circuit; the output end of the subtraction circuit is connected to a channel of the first analog channel selector via the linear optocoupler isolation circuit.

[0019] In a second aspect, the present invention further provides a sampling method for a multi-channel stray current monitoring sensor, comprising the following steps:

[0020] Step S1: Select a channel through the processor, that is, select a voltage input analog-to-digital converter;

[0021] Step S2: setting the sampling parameters of the analog-to-digital converter, including range, channel and rate;

[0022] Step S3: Continuously sample a preset number of times and take the average value as the actual sampling value;

[0023] Step S4: switch channels and select the next voltage input analog-to-digital converter;

[0024] Step S5: cyclically executing steps S1 to S4 six times to complete a round of sampling of six voltages in a preset order;

[0025] Step S6: Execute step S5 repeatedly during the sampling period.

[0026] Preferably, the preset number of times is 10, the duration of each round of sampling is 1 second, and the total duration of sampling each voltage in each round is 20 milliseconds.

[0027] The technical solution provided by the present invention can realize the collection of six-channel voltage signals through the front-end sampling module and the rail sampling circuit, support the analysis and evaluation of the degree of stray current corrosion, improve the accuracy of judging the degree of safety hazards faced by passengers and electrical equipment, and reduce the risk of safety hazards in urban rail transit. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a principle block diagram of a multi-channel stray current monitoring sensor provided in one embodiment of the present invention.

[0029] Figure 2 4 is a topological diagram of a front-end sampling circuit and a linear optocoupler isolation circuit in one embodiment of the present invention.

[0030] Figure 3 FIG. 4 is a topological diagram of an RC filter circuit in an embodiment of the present invention.

[0031] Figure 4 FIG. 4 is a topological diagram of an emitter follower in one embodiment of the present invention.

[0032] Figure 5 It is a topological diagram of a first-order active filter circuit in one embodiment of the present invention.

[0033] Figure 6 FIG. 4 is a topological diagram of a subtraction circuit in an embodiment of the present invention.

[0034] Figure 7 FIG. 4 is a topological diagram of a linear optocoupler isolation circuit in one embodiment of the present invention.

[0035] Figure 84 is a topological diagram of a rail sampling circuit in one embodiment of the present invention.

[0036] Fig. 9 The figure is a sampling logic block diagram of two small signals in one embodiment of the present invention.

[0037] Fig.10 The figure is a sampling logic block diagram of six analog quantities in one embodiment of the present invention.

[0038] Fig.11 This is a timing diagram of simulating the opening of a switch per second in an embodiment of the present invention.

[0039] Fig.12 The figure is a logic flow chart of each voltage sampling in one embodiment of the present invention.

[0040] Fig.13 FIG. 4 is a topological diagram of a power supply circuit in one embodiment of the present invention. DETAILED DESCRIPTION

[0041] Hereinafter, the technical solution provided by the present invention will be further elaborated in combination with embodiments and drawings.

[0042] Example 1

[0043] like Figure 1 As shown, this embodiment provides a six-channel stray current monitoring sensor (hereinafter referred to as "sensor" in this embodiment).

[0044] Specifically, the analog quantities collected by the sensor include the voltage of the return rail to the ground (rail-ground voltage), the voltage of the ballast structure to the ground (junction-ground voltage), the voltage of the return rail to the ballast structure (rail junction voltage), the voltage of the ballast structure to the reference electrode (junction ratio voltage) and the corresponding two 10m rail longitudinal voltages on the two parallel rails, which are then transmitted to analog selection channel 1.

[0045] The acquisition range and accuracy of each voltage are shown in Table 1.

[0046] Table 1 Technical parameters of a multi-channel stray current monitoring sensor

[0047]

[0048] The sensor is equipped with two 4-bit analog terminals. Among them, the P1 terminal is connected to the running rail, ground bar, structural steel bar and reference electrode respectively. Inside the sensor, two by two are combined into four groups of analog voltage sampling: rail-to-ground voltage, junction-to-ground voltage, rail-to-junction voltage and junction ratio voltage, with a voltage range of (DC5~200V).

[0049] In the figure, CAN (Controller Area Network) is the controller area network bus, ACD (Analog to Digital Converter) is the analog-to-digital converter, AUX interface (Auxiliary) refers to the audio input interface, and P1 and P2 represent sampling terminals.

[0050] like Figure 2 As shown in the figure, for each voltage, the front-end sampling circuit is mainly composed of RC filtering (Resistance Capacitance Filtering), an emitter follower, a first-order reverse active filter, a subtraction circuit and a linear optocoupler isolation. The RC circuit is responsible for filtering the analog signal input stage, proportionally reducing the large-range signal after the resistor divider, and overvoltage clamping protection of the TVS (Transient Voltage Suppressor). The emitter follower is responsible for matching the impedance of the front and rear stage circuits to increase the signal driving capability. The main function of the first-order reverse active filter and the subtraction circuit is to superimpose a reference voltage on the analog signal to eliminate negative signals, which is conducive to passing through the linear optocoupler isolation of the rear stage.

[0051] like Figure 3 As shown in the figure, the input resistor in series at the input end of the RC circuit with TVS protection is 10 1206 package resistors in series. Since the safety voltage of the 1206 package resistor is AC250V, in order to be compatible with the input overvoltage AC2KV, the input resistor adopts a mode of 10 1206 package resistors in series plus TVS protection. For input analog quantities of different ranges, the voltage divider value of R11 and the first 10 resistors is changed, and the maximum tolerable overvoltage U max Calculate the resistance value of the 1206 resistor to select the appropriate resistance value.

[0052]

[0053] In the formula, R is Figure 3 The total input resistance in is P. Figure 3 The total power in the input resistor.

[0054] TVS device T1 uses PESD12VL1BA, which can clamp the voltage at 12V to protect the subsequent chips from being burned by overvoltage, and has extremely low leakage current, so the effect on signal distortion can be ignored. The output voltage value ADCo1 of the RC filter circuit is:

[0055]

[0056] make The ratio is k, and the formula can be simplified to:

[0057] ADCo1=V in k.

[0058] For anti-interference measures, it is most reliable to filter out interference at the front end. If the interference enters the subsequent op amp circuit, it will be very difficult to handle. The analog front end also adds a 100nF ceramic capacitor C2 and the input resistor to form an RC filter circuit. External interference will be greatly weakened when passing through this circuit, preventing it from entering the subsequent circuit, which can effectively suppress interference.

[0059] like Figure 4 As shown,

[0060] ADCo2 = ADCo1;

[0061] Where ADCo2 is the output voltage value of the emitter follower.

[0062] The input impedance of the emitter follower can be equivalent to infinity, while the output impedance can be equivalent to zero. Therefore, placing the emitter follower after the RC circuit can well match the impedance of the previous and next stages.

[0063] like Figure 5 As shown, take R21 = R19, the signal transfer formula in the above figure is:

[0064] ADCo3=-ADCo2;

[0065] Where ADCo3 is the output voltage value of the first-order active filter circuit.

[0066] The first-order active filter circuit is implemented with operational amplifiers and resistors and capacitors, which can dynamically filter out each harmonic, and the filtering effect is better than that of passive filtering. In addition, the load impedance will not affect the performance of the filter, and cascading multiple filters will not cause a decrease in signal gain.

[0067] like Figure 6 As shown, in the subtraction circuit, R12=R16, REF2V5 is a 2.5V reference voltage source, and R13 is 3 times the resistance of R14. Substituting the formulas of the previous circuit in turn, we can deduce:

[0068] ADCo4=1.25-ADCo3;

[0069] ADCo4=1.25+ADCo2;

[0070] ADCo4=1.25+ADCo1;

[0071] ADCo4=V in k+1.25;

[0072] Where ADCo4 is the output voltage value of the subtraction circuit.

[0073] like Figure 7As shown, the high-precision linear optocoupler HCNR201 is used for analog isolation, which can not only ensure the linear accuracy of the analog signal, but also prevent external interference from affecting the CPU end, and better ensure the stability of the system operation. R15 is used to limit the driving current within the specified range of the optocoupler HCNR201; the output voltage end of the left op amp drives the LED of the optocoupler 1 and 2 pins to emit light after the current is limited by R17, and the photoreceptors inside the optocoupler 3, 4 pins and 5, 6 pins generate equivalent currents, among which the photoreceptors of the optocoupler 3, 4 pins as negative feedback can make the current generated by the optocoupler 1, 2 pins consistent with the current generated by the photoreceptors of the optocoupler 5, 6 pins. This current passes through R20 to generate the output voltage ADCo5 after isolation. If the resistance values ​​of R17 and R20 are consistent, the input voltage can be made the same as the output voltage. The role of C3 and C4 is to form an RC circuit with the corresponding resistors R17 and R20 to filter out noise to stabilize the signal.

[0074] The circuit transfer formula is:

[0075] ADCo5 = ADCo4;

[0076] Where ADCo5 is the output voltage value after linear optocoupler isolation.

[0077] Then the transfer formula of the entire front-end sampling circuit is:

[0078] V out =V in k+1.25;

[0079] From this formula, we can know that the analog quantity is from input V in To output V out , within the measuring range, the circuit performs linear transformation on the signal, so that the external analog signal is linearly transformed into the voltage range of [0~2.5V], which is conducive to the sampling of the analog-to-digital converter (AD chip).

[0080] The front-end sampling circuit is an original improvement and combination of mature circuit submodules. By modifying the resistance and capacitance parameters, it can be used in various engineering applications with large interference and high precision requirements ranging from 100mV to 2kV. In practical applications, the above circuit submodules can be split and combined in new ways according to needs.

[0081] like Figure 8As shown, a small signal analog sampling circuit is used as the rail sampling circuit to collect the two rail voltage signals corresponding to the parallel rails and transmit them to analog channel selection 2. When the subway is running, the load current flows back to the negative pole of the power supply through the running rail. Because the average impedance of each meter of the rail is about 30uΩ, a very small voltage will be generated when the current flows through. By measuring the voltage of the 10m rail, the current on the rail can be calculated. The intelligent sensor has a terminal that is specifically used to sample the voltage of 2 10m rails, with a range of 15mV and 1V respectively. In order to solve the functions of two-way sampling, small signal, high precision, and compatibility with 2 sampling ranges. The design scheme of using analog switches to switch channels, direct input of differential signals, and software switching of sampling ranges.

[0082] like Figure 8 , Fig. 9 As shown, (GA+, GA-) is the analog input of 10m rail A, (GB+, GB-) is the analog input of 10m rail B, and (AIN1+, AIN1-) is the differential signal connected to the AD chip for analog sampling. SelChA and SelChB are the control pins for sampling two or one. KAQY214STLD is an analog switch. The four resistors (R4~R7) are to prevent short circuit when rails A and B are sampled and turned on at the same time, and to share the excessive input voltage. The resistance value of the resistor is (2.4K-2W). During normal operation, channels A and B will only be turned on once per second, and each time they are turned on for 20mS. When a channel is turned on, if the input voltage is too large, AIN1 will be clamped at 5V by the ESD (Electro-Static Discharge) device T1, and the remaining voltage will be applied to the two resistors. Such design and operation logic can ensure that the device will not burn out when the input overvoltage reaches DC500V.

[0083] To enhance the anti-interference performance, C66 forms an RC filter with the front-end resistor to filter the interference of external input. The two pull-up resistors and ground capacitors on the differential input can stabilize the common-mode potential of the input signal and prevent the jitter of the sampling signal. This circuit can not only meet the requirements of small signal 15mV high-precision (0.2%) sampling and input high voltage resistance, but also can be switched to 1V range sampling by AD chip software, which is suitable for high voltage, high current and strong interference application scenarios on site. The small signal analog switching circuit is specially designed for sampling two sets of 10m subway rail voltages, and it also achieves the expected effect in field applications.

[0084] like Fig.10As shown, inputting four voltage analog signals into analog channel selection 1 and two rail voltage analog signals into analog channel selection 2 is equivalent to connecting all the processed six voltage model signals to the 6-select-1 analog switch component. At the beginning of each sampling, the CPU (Central Processing Unit) needs to select the analog switch sampling channel through the IO port to ensure that only one analog quantity can enter the AD conversion chip at any time. Then set the sampling parameters of the AD chip such as range, channel, rate and other parameters through the SPI bus, and then start the AD conversion. After completion, the data is taken out through the SPI bus and put into the cache until the average value is calculated after 10 consecutive samplings to calculate the actual sampling value. When the channel is sampled, switch to the next sampling channel and restart the sampling cycle. The CPU only controls the entire analog sampling timing through the isolated SPI (Serial Peripheral Interface) bus and IO port, and achieves good isolation from the interference of the analog front end.

[0085] Among them, the chip signals and parameters for realizing digital isolation and analog switch functions are shown in Table 2.

[0086] Table 2 Digital isolation and analog switch parameters

[0087]

[0088] like Fig.11 As shown in the figure, for six channels, all channels are trained once per second, and each channel is turned on for about 20ms. This can effectively prevent external interference and high voltage input from damaging the device, especially for sampling connected to 10m rails, where there is a lot of interference when a train passes by.

[0089] The software control flow of single analog sampling is as follows: Fig.12 As shown in the figure, the function submodule is executed in the main function, and the timing of starting each sampling is controlled by the timer, which can well ensure that the six-way analog sampling is carried out under the beat of the unified timing and accurately determine the time of each sampling. The sensor power input is DC7V~DC48V, because the AC220V may be connected incorrectly during on-site installation and debugging. The sensor design takes into account that when connected to AC220V, only the fuse is disconnected without burning other devices.

[0090] The power supply is designed as Fig.13As shown. When the power supply is connected to AC220V by mistake, the instantaneous high voltage will trigger the varistor RV1 to conduct and trigger F1 to burn out, thereby protecting the subsequent circuit. At the moment when F1 does not burn out, the common mode inductor and the subsequent TVS and EC1 will prevent the voltage from rising suddenly. Because F1 is a one-time fast-fuse insurance, the subsequent protection circuit can limit the voltage within a safe range in a short millisecond time, thereby ensuring the safety of the subsequent circuit. This circuit is an improved circuit.

[0091] The stray current monitoring sensor is designed to monitor the insulation and stray current leakage of the track. After real-time monitoring of the on-site analog quantity, the sampled data will be analyzed on the software as follows.

[0092] Original polarization potential: the potential between the ballast structure and the reference electrode.

[0093] Bulk potential: The measurement time is in the early morning (the time can be set) every day when there are no trains passing. At this time, in the absence of stray current disturbance, the measured original polarization potential is a stable value, which is called the bulk potential.

[0094] Polarization instantaneous value: Polarization instantaneous value = original polarization potential - bulk potential.

[0095] Forward polarization average value: the sum of polarization instantaneous values ​​greater than 0 divided by the number of sampling times of polarization instantaneous values ​​greater than 0 within a fixed time period (the time period can be set by software);

[0096] Forward polarization average value: the sum of the instantaneous polarization values ​​less than 0 in a fixed time period divided by the number of sampling times when the instantaneous polarization value is less than 0;

[0097] Maximum forward polarization value: the maximum value of the data whose instantaneous polarization value is greater than 0 within a fixed time period;

[0098] Maximum negative polarization value: the maximum value of the data whose instantaneous value of polarization is less than 0 within a fixed time period;

[0099] Instantaneous value of rail junction potential: the real-time voltage value of the return-conformed rail on the ballast structure.

[0100] Instantaneous value of rail-to-ground potential: the real-time voltage value of the return rail to the ground bar.

[0101] Instantaneous value of junction ground potential: the real-time voltage value of the ballast structure relative to the ground rail.

[0102] When the stray current monitoring sensor processes the above data, it only stores one data packet in a fixed time period. The data storage adopts polling coverage method and can save up to 24 hours of data. The host computer can read the sensor data through the bus.

[0103] Based on the above embodiments and drawings, it can be seen that the present invention can simultaneously monitor the voltage of the return rail to the ballast structure, the voltage of the ballast structure to the ground (grounding flat steel), the longitudinal voltage of the 10m rail, the voltage of the return rail to the ground, and the voltage of the ballast structure to the reference electrode. The sensor provided by the present invention has the characteristics of high sampling accuracy, strong anti-interference ability, strong fault tolerance, etc. The input is DC7V~DC48V. The sensor design takes into account that when connected to AC220V, only the fuse is disconnected without burning other devices.

[0104] In summary, the technical solution provided by the present invention can realize the collection of six-channel voltage signals through the front-end sampling module and the rail sampling circuit, support the analysis and evaluation of the degree of stray current corrosion, improve the accuracy of judging the degree of safety hazards faced by passengers and electrical equipment, and reduce the risk of safety hazards in urban rail transit.

[0105] Furthermore, each preferred scheme has achieved the following beneficial effects on the basis of achieving the above beneficial effects: the RC filter circuit with TVS protection function can protect the safety of the subsequent chip; the emitter follower can achieve good matching of the impedance of the front and rear stages; the first-order active filter circuit can dynamically filter out each harmonic without being affected by the load; and the use of multiple rounds of multiple-choice channels can sequentially sample multiple signals; the mutual cooperation of the above circuit sub-modules can achieve sampling work with high precision, strong anti-interference ability and strong fault tolerance.

Claims

1. A multi-channel stray current monitoring sensor, characterized in that: It includes a front-end sampling module, a rail sampling circuit, a first analog channel selector, a second analog channel selector, an analog-to-digital converter and a processor; The front-end sampling module includes a first front-end sampling circuit, a second front-end sampling circuit, a third front-end sampling circuit and a fourth front-end sampling circuit, and is connected to the four channels of the first analog channel selector in a one-to-one correspondence; The first front-end sampling circuit samples the rail-to-ground voltage, the second front-end sampling circuit samples the junction-to-ground voltage, the third front-end sampling circuit samples the rail-to-junction voltage, and the fourth front-end sampling circuit samples the junction ratio voltage; The rail sampling circuit collects the voltages of two 10m rails at the same position of the parallel rails and inputs them into two channels of the second analog channel selector accordingly; An output terminal of the first analog channel selector is connected to a first input terminal of the analog-to-digital converter, and an output terminal of the second analog channel selector is connected to a second input terminal of the analog-to-digital converter; The output of the analog-to-digital converter is connected to the processor; Control terminals of the first analog channel selector and the second analog channel selector are both connected to the processor.

2. A multi-channel stray current monitoring sensor as claimed in claim 1, characterized in that: It also includes a linear optocoupler isolation circuit; The number of the linear optocoupler isolation circuits is 4, and the input end of each linear optocoupler isolation circuit is connected to the output end of a front-end sampling circuit, and the output end is connected to a channel of the first analog channel selector.

3. A multi-channel stray current monitoring sensor as claimed in claim 1, characterized in that: Each front-end sampling circuit includes an RC filtering circuit; In the RC filter circuit, a TVS device is provided in parallel with a resistor, an input resistor is provided at the input end, and an output end is connected to a channel of a first analog channel selector.

4. A multi-channel stray current monitoring sensor as claimed in claim 1, characterized in that: Each front-end sampling circuit includes an emitter follower; The output terminal of the emitter follower is connected to a channel of the first analog channel selector.

5. A multi-channel stray current monitoring sensor as claimed in claim 1, characterized in that: Each front-end sampling circuit includes a first-order reverse active filtering circuit and a subtraction circuit; The output terminal of the first-order inverse active filter circuit is connected to a channel of the first analog channel selector via a subtraction circuit.

6. A multi-channel stray current monitoring sensor as claimed in claim 1, characterized in that: Each front-end sampling circuit includes an RC filter circuit, an emitter follower, a first-order reverse active filter circuit and a subtraction circuit connected in series in sequence; In the RC filter circuit, a TVS device is connected in parallel with a resistor, and an input resistor is provided at the input end; the output end of the subtraction circuit is connected to a channel of the first analog channel selector.

7. A multi-channel stray current monitoring sensor as claimed in claim 6, characterized in that: It also includes a linear optocoupler isolation circuit; The output end of the subtraction circuit is connected to a channel of the first analog channel selector via a linear optocoupler isolation circuit.

8. A sampling method for a multi-channel stray current monitoring sensor as claimed in claim 1, characterized in that: The following steps are involved: Step S1: Select a channel through the processor, that is, select a voltage input analog-to-digital converter; Step S2: setting the sampling parameters of the analog-to-digital converter, including range, channel and rate; Step S3: Continuously sample a preset number of times and take the average value as the actual sampling value; Step S4: switch channels and select the next voltage input analog-to-digital converter; Step S5: cyclically executing steps S1 to S4 six times to complete a round of sampling of six voltages in a preset order; Step S6: Execute step S5 repeatedly during the sampling period.

9. The sampling method according to claim 8, characterized in that: The preset number of times is 10, the duration of each round of sampling is 1 second, and the total sampling duration of each voltage in each round is 20 milliseconds.

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