CN211652989U - Power real-time detection circuit and monitoring module suitable for three-phase water heater - Google Patents

Abstract

A power real-time detection circuit suitable for a three-phase water heater includes three identical measurement circuits, and also includes the same first, second and three-phase detection circuits; any phase detection circuit includes a power supply circuit, a voltage acquisition circuit, and a current acquisition circuit. circuit and a measurement circuit. A three-phase water heater monitoring module includes a structure and a circuit part; the structure part is a casing, and the external wiring terminals of the circuit part are arranged on the casing; the circuit part is located in the casing, and it includes a power supply circuit, a power Real-time detection circuit, switch value input circuit, sensor detection circuit, 485 communication circuit, electric heating circuit and control circuit; the output terminals of the power real-time detection circuit, switch value input circuit and sensor detection circuit are connected to the control circuit input terminal; the data of the control circuit The communication terminal is connected to the 485 communication terminal through the 485 communication circuit; the control output terminal of the control circuit is connected to the control input terminal terminal of the electric heating circuit.

Description

Power real-time detection circuit and monitoring module for three-phase water heater

technical field

The technology relates to the field of electronic technology, in particular to a power real-time detection circuit suitable for a three-phase water heater.

Background technique

In the prior art, the most common power measuring device is a single-phase measuring device, which cannot meet the needs of three-phase water heater power measurement and monitoring, and a three-phase power meter cannot directly use a single-phase measuring device. Three-phase water heaters are mostly used in the industrial field, and their control is mostly PLC. When monitoring, a sensor circuit needs to be set up to control the water heater. In the case of three-phase solar water heaters, due to the introduction of solar heat exchangers as heat sources, when encountering rainy weather or other conditions (such as excessive hot water consumption), the heat energy from the heat exchangers is not enough to provide energy for heating water. Three-phase electric auxiliary heating. The working conditions of three-phase solar water heaters are more complicated, and more sensor circuits need to be introduced. In the water heater products, due to the influence of the humidity of its use scene, the waterproof requirements of the circuit are relatively high, and the workload of design and construction is relatively large.

SUMMARY OF THE INVENTION

In order to solve the above problems in the prior art, the utility model proposes a real-time power detection circuit suitable for a three-phase water heater, including a measurement circuit. The measuring circuits have the same three; also include the same first, second and three-phase detection circuits;

Any phase detection circuit includes a power supply circuit, a voltage acquisition circuit, a current acquisition circuit and a measurement circuit;

A. The power supply circuit includes an ordinary transformer T1, a bridge rectifier circuit and a power supply filter circuit;

The primary side of the ordinary transformer T1 is connected between the power phase line and the neutral line respectively;

The bridge rectifier circuit includes the first diode D1 and the second diode D2; the anode of the first diode D1 is connected to one end of the secondary side of the ordinary transformer T1, and the anode of the second diode D2 is connected to the other end of the secondary side of the ordinary transformer T1, The midpoint of the secondary side of the ordinary transformer T1 is grounded; the cathode of the first diode D1 and the cathode of the second diode D2 are jointly used as the DC output end of the bridge rectifier circuit; the input end of the power filter circuit is connected to the bridge rectifier circuit. The DC output terminal, the input terminal of the power filter circuit is connected to the power input terminal of the measurement circuit;

B. The current collection circuit includes a voltage transformer T2 and a voltage signal filter circuit; the primary side of the voltage transformer T2 is respectively connected between the power phase line and the neutral line;

The "+" output terminal and the "-" output terminal of the voltage signal filter circuit are respectively connected to the voltage signal input "+" and "-" terminals of the measuring circuit;

C. The current acquisition circuit includes a current transformer T3 and a current signal filter circuit; the primary side of the current transformer T3 is respectively connected between the power phase line and the neutral line;

The "+" output terminal and the "-" output terminal of the current signal filter circuit are respectively connected to the current signal input "+" and "-" terminals of the measurement circuit;

The circuit structure of the voltage signal filter circuit and the current signal filter circuit is the same, they are bridge filter circuits, and the bridge filter circuit includes: the same first and second isolation resistors; the same first and second voltage dividing resistors; the same first and second voltage divider resistors; One, two filter ground capacitors;

The first end of the first isolation resistor is grounded, the second end of the first isolation resistor is connected to the first end of the first voltage divider resistor; the second end of the first voltage divider resistor is grounded through the first filter grounding capacitor; the first isolation resistor The second end of the output signal is used as the "+" end of the output signal;

The first end of the second isolation resistor is grounded, and the second end of the second isolation resistor is connected to the first end of the second voltage divider resistor; the second end of the second voltage divider resistor is grounded through the second filter grounding capacitor; the second isolation resistor The second end of the output signal is used as the "-" end of the output signal;

Connect a filter capacitor between the "+" terminal and the "-" terminal of the output signal.

The same-phase detection circuit power supply circuit, voltage acquisition circuit, and current acquisition circuit are all connected to the same phase line of the three-phase power supply.

further:

It also includes a power-off voltage acquisition circuit, which includes two isolation resistors connected in series; one end of the third isolation resistor is connected to the DC output end of the bridge rectifier circuit, one end of the fourth isolation resistor is grounded, and the third and fourth isolation resistors are connected to the ground. The connection end between the isolation resistors is connected to the power-down voltage detection end of the measurement circuit. (Calculate the resistance ratio of the first and second isolation resistors from the power-down voltage correlation.)

The output terminal of the power filter circuit includes an analog voltage "+" output terminal and a digital voltage "+" output terminal; a resistor and a capacitor are connected in series between the analog voltage "+" output terminal and the ground terminal, and the resistor is isolated from the analog voltage "+" Between the output terminal and the digital voltage "+" output terminal, the digital voltage "+" output terminal is grounded through the capacitor.

The measurement circuit is CS5460A; the oscillation signal input terminals of CS5460A are respectively connected to the two poles of the crystal oscillator; the ground terminal of CS5460A is directly grounded; the reference voltage terminal of CS5460A is grounded through a capacitor.

A three-phase water heater monitoring module using the above-mentioned power real-time detection circuit includes a structural part and a circuit part; the structural part is a casing, and the casing is provided with an external connection terminal of the circuit part. The circuit part is located in the casing, and the casing has a waterproof structure;

The circuit part includes a power supply circuit, a real-time power detection circuit, a switch input circuit, a sensor detection circuit, a 485 communication circuit, an electric heating circuit and a control circuit, which are carried on the PCB board;

The AC input terminal of the power supply circuit is connected to the power supply terminal located on the housing, and the AC power is converted into DC power. ;

The output ends of the power real-time detection circuit, the switch input circuit and the sensor detection circuit are connected to the input end of the control circuit;

The data communication end of the control circuit is connected to the 485 communication terminal through the 485 communication circuit;

The control output end of the control circuit is connected to the control input end connection terminal of the electric heating circuit.

further:

The sensor detection circuit includes a temperature detection circuit and a liquid level detection circuit;

In the temperature detection circuit, the output end of the temperature sensor is connected to the AD conversion circuit of the three-phase water heater monitoring module through the terminal, and the digital signal output end of the AD conversion circuit is connected to the control circuit;

In the liquid level detection circuit, the output end of the liquid level transmitter is connected to the AD conversion circuit of the three-phase water heater monitoring module through the wiring terminal, and the digital signal output end of the AD conversion circuit is connected to the control circuit.

The electric heating circuit includes three-phase loops, the three-phase loops are the same, and they are respectively connected between the power supply phase line and the neutral line;

For any phase loop: the phase line and the neutral line are respectively connected to the corresponding terminals of the module; the switch on the phase line is controlled by a relay, and the control end of the relay is connected between the high level and the ground; connect the control circuit The control output end of the relay is connected to the base of a triode through a protective resistor, and the control end of the relay and the ground are respectively connected to the collector and the emitter of the triode.

The 485 communication circuit is a circuit with a 485 communication chip as the core; an optocoupler is connected between the 485 communication chip and the signal communication end of the control circuit;

The 485 communication chip and the terminal are connected correspondingly. There is an absorption circuit between the 485+ and 485- pins. The 485+ and 485- pins are connected to high level and ground through pull-up resistors and pull-down resistors, respectively. 485+ and 485 - Resistors connected between pins to reduce reflections of signals transmitted on the road.

The switch input circuit is a circuit with an optocoupler as the core, the input end of the optocoupler is connected to the corresponding connection terminal, and the output end of the optocoupler is connected to the control circuit.

The main features of this module are modularization, miniaturization and improved protection performance. The function of the control circuit in this module is limited to converting the signal format and issuing a control level of 0 or 1 according to the signal reaching the threshold, and there is no algorithm function that requires creative work.

Compared with the prior art, the three-phase solar water heater electric energy monitoring and control module has high integration, small volume and good protection performance, and is convenient to be used as an independent module. All unit circuits are integrated in the module, which provides switch I/O interfaces, analog interfaces, Ethernet and serial communication interfaces, etc. These interfaces are used to communicate with the PLC of the control system.

Description of drawings

Figure 1 is a schematic diagram of the power real-time detection circuit of this example.

Figure 2 is a schematic block diagram of a solar water heater monitoring module;

Figure 3 is a schematic diagram of the sensor detection circuit of this example.

Figure 4 is a schematic diagram of the electric heater circuit of this example.

Figure 5 is a schematic diagram of the 485 communication circuit of this example.

Figure 6 is a schematic diagram of the switch input circuit of this example.

FIG. 7 is a schematic diagram of the external structure of the solar water heater monitoring module.

FIG. 8 is a schematic view from the left side of FIG. 7 .

In the figure: housing 1, terminal block 2, slot 3 corresponding to the DIP guide rail, and screw mounting plate 4.

Detailed ways

A power real-time detection circuit suitable for a three-phase water heater includes a measurement circuit. The measuring circuits have the same three; also include the same first, second and three-phase detection circuits;

Any phase detection circuit includes a power supply circuit, a voltage acquisition circuit, a current acquisition circuit and a measurement circuit;

A. The power supply circuit includes an ordinary transformer T1, a bridge rectifier circuit and a power supply filter circuit;

The primary side of the ordinary transformer T1 is connected between the power phase line and the neutral line respectively;

The bridge rectifier circuit includes the first diode D1 and the second diode D2; the anode of the first diode D1 is connected to one end of the secondary side of the ordinary transformer T1, and the anode of the second diode D2 is connected to the other end of the secondary side of the ordinary transformer T1, The midpoint of the secondary side of the ordinary transformer T1 is grounded; the cathode of the first diode D1 and the cathode of the second diode D2 are jointly used as the DC output end of the bridge rectifier circuit; the input end of the power filter circuit is connected to the bridge rectifier circuit. The DC output terminal, the input terminal of the power filter circuit is connected to the power input terminal of the measurement circuit;

B. The current collection circuit includes a voltage transformer T2 and a voltage signal filter circuit; the primary side of the voltage transformer T2 is respectively connected between the power phase line and the neutral line;

The "+" output terminal and the "-" output terminal of the voltage signal filter circuit are respectively connected to the voltage signal input "+" and "-" terminals of the measuring circuit;

C. The current acquisition circuit includes a current transformer T3 and a current signal filter circuit; the primary side of the current transformer T3 is respectively connected between the power phase line and the neutral line;

The "+" output terminal and the "-" output terminal of the current signal filter circuit are respectively connected to the current signal input "+" and "-" terminals of the measurement circuit;

The circuit structure of the voltage signal filter circuit and the current signal filter circuit is the same, they are bridge filter circuits, and the bridge filter circuit includes: the same first and second isolation resistors; the same first and second voltage dividing resistors; the same first and second voltage divider resistors; One, two filter ground capacitors;

The first end of the first isolation resistor is grounded, the second end of the first isolation resistor is connected to the first end of the first voltage divider resistor; the second end of the first voltage divider resistor is grounded through the first filter grounding capacitor; the first isolation resistor The second end of the output signal is used as the "+" end of the output signal;

The first end of the second isolation resistor is grounded, and the second end of the second isolation resistor is connected to the first end of the second voltage divider resistor; the second end of the second voltage divider resistor is grounded through the second filter grounding capacitor; the second isolation resistor The second end of the output signal is used as the "-" end of the output signal;

Connect a filter capacitor between the "+" terminal and the "-" terminal of the output signal.

In this example:

It also includes a power-off voltage acquisition circuit, which includes two isolation resistors connected in series; one end of the third isolation resistor is connected to the DC output end of the bridge rectifier circuit, one end of the fourth isolation resistor is grounded, and the third and fourth isolation resistors are connected to the ground. The connection end between the isolation resistors is connected to the power-down voltage detection end of the measurement circuit. (Calculate the resistance ratio of the first and second isolation resistors from the power-down voltage correlation.)

The output terminal of the power filter circuit includes an analog voltage "+" output terminal and a digital voltage "+" output terminal; a resistor and a capacitor are connected in series between the analog voltage "+" output terminal and the ground terminal, and the resistor is isolated from the analog voltage "+" Between the output terminal and the digital voltage "+" output terminal, the digital voltage "+" output terminal is grounded through the capacitor.

The measurement circuit is CS5460A; the oscillation signal input terminals of CS5460A are respectively connected to the two poles of the crystal oscillator; the ground terminal of CS5460A is directly grounded; the reference voltage terminal of CS5460A is grounded through a capacitor.

Figure 1 is a power supply power detection circuit of one phase in the real-time power detection circuit of this example, which adopts a bidirectional power measurement chip CS5460A, and the isolation from the power supply line is realized by three transformers. The other two-phase power supply power detection circuit is the same as the power supply power detection circuit of this phase, and its T1 to T3 are respectively connected between UB and UN and between UC and UN.

T1 is an ordinary transformer, used to provide the DC power supply of CS5460A. After rectification, it is connected to pin 14 and pin 3 of the first CS5460A; T2 is a voltage transformer, which is connected to the voltage signal input of the first CS5460A after filtering. Pin 9 is connected to pin 10; T3 current transformer is used to measure the current of the power line, and after filtering, it is connected to pin 16 and pin 15 of the first CS5460A.

Taking the application of the three-phase power detection circuit in the solar water heater monitoring module as an example, the utility model is further described.

The main heat source of solar water heaters comes from solar heat exchangers. However, in the case of rainy weather or other conditions (such as hot water consumption too fast, etc.), the heat energy from the heat exchanger is not enough to provide the energy for heating water, and three-phase electric auxiliary heating is required. At this time, the plant area power monitoring system needs to know the power consumption information for the water heater.

Therefore, the three-phase water heater monitoring module using the three-phase power detection circuit can solve the above problems.

Referring to Figure 2, the solar water heater monitoring module using the power detection circuit includes a power supply circuit, an electrical energy power detection circuit (that is, the three-phase power real-time detection circuit), a sensor detection circuit (including a temperature detection circuit and a liquid level detection circuit), 485 A communication circuit, a switching input circuit and an electric heating control circuit; the power supply circuit converts alternating current to direct current, which is required by each functional circuit in the monitoring device.

The temperature detection circuit, the liquid level detection circuit, the 485 communication circuit, the digital input circuit and the electric heating circuit are all electrically connected with the controller.

The input end of the temperature detection circuit is connected with the output end of the temperature sensor HSM-ALT, the input end of the liquid level detection circuit is connected with the output end of the liquid level transmitter HD-136, and the control output end of the electric heating circuit is connected with the three-phase electric heating connected to the device DN40.

In this example, the controller is a circuit with 51 series single chip STC89C58RD as the core.

In the power detection circuit of the power supply, refer to Figure 1:

The SDI and SDO signal output ports of CS5460A can be used to output data. These two ports can be used to connect with the data input end of the single-chip microcomputer. In this example, it is connected to the P2.7 and P2.6 ports of the controller.

The chip select 7 pin of CS5460A is used to connect with the chip select signal output end of the microcontroller, in this case, it is connected to the P3.2 port of the controller.

The 19-pin of CS5460A is used to obtain the reset signal output by the single-chip microcomputer. In this example, it is connected to the RST port of the controller.

The 20-pin of CS5460A is used to obtain the interrupt output signal of the single-chip microcomputer. In this example, it is connected to the P3.3 port of the controller.

Pins 1 and 2 of CS5460A are connected to an external oscillator circuit to obtain crystal oscillator signals.

13 feet and 4 feet of CS5460A are grounded directly.

The 12-pin and 11-pin of CS5460A are grounded after connecting the C12 capacitor in series to obtain the reference voltage.

The connection between the bidirectional power measurement chip CS5460A and the controller in the other two-phase power detection circuits used in this example is similar to this phase circuit.

Referring to Figure 3, the sensor detection circuit includes a temperature detection circuit and a liquid level detection circuit. In the temperature detection circuit, the 1-pin and 2-pin of the temperature sensor HSM-ALT are connected to the power supply on the left, and the 3-pin and 4-pin of the signal output terminal are connected to the I+ and I- ports of the AD conversion circuit. .4 Port connection, input temperature information. In the liquid level detection circuit, the 1-pin 2-pin of the liquid level transmitter HD-136 is connected to the power supply on the left, and the 3-pin and 4-pin of the signal output port are connected to the input terminals ADCout+ and ADCout- of the AD conversion circuit. After AD conversion, the signal The output terminal D0 is connected with the controller P1.5 to output the liquid level signal.

See Figure 4, the electric heating circuit adopts DN40 three-phase electric heater, the pins UA, UB, UC, UN are respectively connected to the three-phase wires UA, UB, UC, UN to supply power to the DN40 three-phase heater, in the electric heating circuit A relay circuit is added to realize the controller's control of the heater. The relay control circuit is connected to the P1.7 end of the controller. The 1k resistor protects the circuit. When the triode base is at a high level, the triode 2N3904 is turned on and the relay is energized. Pull in, the heater circuit is turned on to start heating.

Referring to Figure 5, the 485 communication circuit uses a 75176 communication chip, the 8-pin VCC terminal is connected to a 5V voltage to supply power to the chip, the TIL117 optocoupler is used to isolate the signal between the bus and the controller, and the voltage regulator tubes D7 and D8 are used to form absorption The circuit protects the transmission end of the 485 bus. Add two pull-up resistors R36 and R40 to the A and B ends of the 485 circuit to prevent the controller from receiving random characters. A 120Ω resistor R38 is connected in series to reduce the reflection of the transmission signal on the line.

Referring to Figure 6, for the switch input circuit, the selected optocoupler model is TPL521-1, the 220V voltage is connected to the switch input circuit through the left port, the resistors R41 and R42 are connected to the circuit to limit the current, and R43 is connected in parallel with the capacitor C33 Filtering, diode D14 is connected in parallel at both ends of the optocoupler to protect the optocoupler, D11 Zener diode is connected in series in the loop to stabilize the voltage, and the collected switching information is connected to the controller P0.5 port input controller.

Referring to Figures 7 and 8, the back of the monitoring module has a card slot corresponding to the DIP rail, which can be installed on the standard DIP rail. At the same time, the 4 mounting plates can also install the monitoring module on the common carrier. Each terminal of the monitoring module will be on two terminal blocks for easy wiring.

The monitoring module of this application example monitors the temperature of the solar hot water and heats the water according to the demand. In this application example:

The temperature sensor detection circuit and the liquid level transmitter detection circuit continuously detect the water temperature and the water storage water level of the water heater, and after passing through the AD conversion circuit, the data is transmitted to the controller through the P1.4 and P1.5 ports.

After the switch quantity detection circuit continuously detects the input condition of the switch quantity, it transmits the switch quantity information to the controller through the P0.5 and P0.6 ports.

After the liquid level and water temperature data are obtained and the threshold conditions are met, the controller P1.7 port controls the electric heater heating circuit to work, the relays K1 and K2 are closed, and the heating circuit is closed for heating.

After the electric heating loop starts to work, the input terminal of the CS5460A of the power detection circuit detects the voltage and current information of the grid, and transmits the power information to the controller through the SDI and SDO ports for power calculation (that is, the product of voltage and current). ). The controller transmits the power data in real time through the 485 communication circuit.

The technical solution solves the following problems of the three-phase solar water heater: (1) when the temperature of the hot water tank has reached the set temperature, the heating power cannot be cut off in time, resulting in excessive water temperature and waste of electric energy; (2) placed on the roof The heat collection system in the solar hot water tank operates normally, but due to the failure of the warm water circulation control system, the hot water heated by the solar energy cannot be delivered to the user's home, so the water heater has been using auxiliary electric heating. However, these problems are usually not noticed by users, especially in collective dormitories, hotels and other occasions where large-scale solar water heaters are used, the daily staff pay little attention to the operation and power consumption of solar water heaters, and the occurrence of the above problems will cause A lot of electricity wasted, increasing electricity bills.

The energy consumption monitoring module of the utility model is used for monitoring/monitoring the temperature of the hot water tank and the electric energy of the water heater. When the temperature of the hot water tank reaches the set temperature, the electric heating is automatically cut off. At the same time, it monitors the energy consumption value of the water heater, judges the fault of the warm water circulation control system of the water heater, and alerts the user to repair the water heater to achieve the purpose of energy saving.

Claims (9)

1. A power real-time detection circuit suitable for a three-phase water heater, comprising a measurement circuit, characterized in that the measurement circuit has the same three; and also includes the same first, second and three-phase detection circuits; Any phase detection circuit includes a power supply circuit, a voltage acquisition circuit, a current acquisition circuit and a measurement circuit; A. The power supply circuit includes an ordinary transformer T1, a bridge rectifier circuit and a power supply filter circuit; The primary side of the ordinary transformer T1 is connected between the power phase line and the neutral line respectively; The bridge rectifier circuit includes the first diode D1 and the second diode D2; the anode of the first diode D1 is connected to one end of the secondary side of the ordinary transformer T1, and the anode of the second diode D2 is connected to the other end of the secondary side of the ordinary transformer T1, The midpoint of the secondary side of the ordinary transformer T1 is grounded; the cathode of the first diode D1 and the cathode of the second diode D2 are jointly used as the DC output end of the bridge rectifier circuit; the input end of the power filter circuit is connected to the bridge rectifier circuit. The DC output terminal, the input terminal of the power filter circuit is connected to the power input terminal of the measurement circuit; B. The current collection circuit includes a voltage transformer T2 and a voltage signal filter circuit; the primary side of the voltage transformer T2 is respectively connected between the power phase line and the neutral line; The "+" output terminal and the "-" output terminal of the voltage signal filter circuit are respectively connected to the voltage signal input "+" and "-" terminals of the measuring circuit; C. The current acquisition circuit includes a current transformer T3 and a current signal filter circuit; the primary side of the current transformer T3 is respectively connected between the power phase line and the neutral line; The "+" output terminal and the "-" output terminal of the current signal filter circuit are respectively connected to the current signal input "+" and "-" terminals of the measurement circuit; The circuit structure of the voltage signal filter circuit and the current signal filter circuit is the same, they are bridge filter circuits, and the bridge filter circuit includes: the same first and second isolation resistors; the same first and second voltage dividing resistors; the same first and second voltage divider resistors; One and two filter ground capacitors; The first end of the first isolation resistor is grounded, the second end of the first isolation resistor is connected to the first end of the first voltage divider resistor; the second end of the first voltage divider resistor is grounded through the first filter grounding capacitor; the first isolation resistor The second end of the output signal is used as the "+" end of the output signal; The first end of the second isolation resistor is grounded, and the second end of the second isolation resistor is connected to the first end of the second voltage divider resistor; the second end of the second voltage divider resistor is grounded through the second filter grounding capacitor; the second isolation resistor The second end of the output signal is used as the "-" end of the output signal; Connect a filter capacitor between the "+" terminal and the "-" terminal of the output signal. 2. The real-time power detection circuit suitable for a three-phase water heater according to claim 1, characterized in that it further comprises a power-down voltage collection circuit, and the power-down voltage collection circuit comprises two isolation resistors connected in series; one end of the third isolation resistor It is connected to the DC output end of the bridge rectifier circuit, one end of the fourth isolation resistor is grounded, and the connection end between the third and fourth isolation resistors is connected to the power-down voltage detection end of the measuring circuit. 3. The power real-time detection circuit suitable for a three-phase water heater according to claim 1, wherein the output end of the power filter circuit comprises an analog voltage "+" output end and a digital voltage "+" output end; A resistor and a capacitor are connected in series between the analog voltage "+" output terminal and the ground terminal. The resistor is isolated between the analog voltage "+" output terminal and the digital voltage "+" output terminal, and the digital voltage "+" output terminal passes through the capacitor. ground. 4. The power real-time detection circuit suitable for a three-phase water heater according to claim 1, wherein the measurement circuit is CS5460A; the oscillation signal input terminals of CS5460A are respectively connected to the two poles of the crystal oscillator; the ground terminal of CS5460A is directly grounded; The reference voltage terminal of CS5460A is grounded through the capacitor. 5. A three-phase water heater monitoring module using the power real-time detection circuit according to any one of claims 1 to 4, comprising a structural part and a circuit part; the structural part is a casing, and a circuit part is provided on the casing. The external wiring terminal is characterized in that the circuit part is located in the casing, and the casing has a waterproof structure; The circuit part includes a power supply circuit, a real-time power detection circuit, a switch input circuit, a sensor detection circuit, a 485 communication circuit, an electric heating circuit and a control circuit, which are carried on the PCB board; The AC input terminal of the power supply circuit is connected to the power supply terminal located on the housing, and the AC power is converted into DC power. ; The output ends of the power real-time detection circuit, the switch input circuit and the sensor detection circuit are connected to the input end of the control circuit; The data communication end of the control circuit is connected to the 485 communication terminal through the 485 communication circuit; The control output end of the control circuit is connected to the control input end connection terminal of the electric heating circuit. 6. The three-phase water heater monitoring module according to claim 5, wherein the sensor detection circuit comprises a temperature detection circuit and a liquid level detection circuit; In the temperature detection circuit, the output end of the temperature sensor is connected to the AD conversion circuit of the three-phase water heater monitoring module through the terminal, and the digital signal output end of the AD conversion circuit is connected to the control circuit; In the liquid level detection circuit, the output end of the liquid level transmitter is connected to the AD conversion circuit of the three-phase water heater monitoring module through the wiring terminal, and the digital signal output end of the AD conversion circuit is connected to the control circuit. 7. The three-phase water heater monitoring module according to claim 5, wherein the electric heating circuit comprises a three-phase loop, the three-phase loops are the same, and they are respectively connected between the power phase line and the neutral line; For any phase loop: the phase line and the neutral line are respectively connected to the corresponding terminals of the module; the switch on the phase line is controlled by a relay, and the control end of the relay is connected between the high level and the ground; connect the control circuit The control output end of the relay is connected to the base of a triode through a protective resistor, and the control end of the relay and the ground are respectively connected to the collector and the emitter of the triode. 8. The three-phase water heater monitoring module according to claim 5, wherein the 485 communication circuit is a circuit with a 485 communication chip as the core; an optical coupling is connected between the 485 communication chip and the signal communication end of the control circuit device; Corresponding connection between the 485 communication chip and the terminal, there is a absorbing circuit between the 485+ and 485- pins, the 485+ and 485- pins are connected to the high level and the ground through the pull-up resistor and the pull-down resistor respectively, 485+ and 485 - Resistors connected between pins to reduce reflections of signals transmitted on the road. 9 . The three-phase water heater monitoring module according to claim 5 , wherein the switch input circuit is a circuit with an optocoupler as the core, the input end of the optocoupler is connected to the corresponding terminal, and the output of the optocoupler is connected to the corresponding terminal. 10 . The terminal is connected to the control circuit.

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