CN212845893U

CN212845893U - Short-circuit fault warning device for RS485 branch line of electric meter

Info

Publication number: CN212845893U
Application number: CN202020921422.3U
Authority: CN
Inventors: 刘长辉
Original assignee: Guangzhou Huaming Electric Power Technology Co ltd
Current assignee: Guangzhou Huaming Electric Power Technology Co ltd
Priority date: 2020-05-27
Filing date: 2020-05-27
Publication date: 2021-03-30
Anticipated expiration: 2030-05-27

Abstract

The utility model discloses an ammeter RS485 branch line short circuit fault warning device, including shell, 220V power cord, still including setting up two way relay drive module, differential amplifier module, voltage comparator module, warning light module and the power module in the shell, power module truns commercial power 220V into 5V constant voltage power supply, still including RS485 branch line interface, RS485 trunk line interface, LED warning light and the power state LED pilot lamp that connects the user's ammeter. The utility model has the following main points that 1) the short-circuit fault of the RS485 branch line port of the electric meter is monitored on line in real time; 2) after the short circuit fault of the RS485 branch line port of the electric meter is monitored, a warning lamp is generated to flash and alarm; 3) and after the short-circuit fault of the RS485 branch line port of the electric meter is monitored, the RS485 fault branch line is disconnected, and the RS485 trunk line is protected.

Description

Short-circuit fault warning device for RS485 branch line of electric meter

Technical Field

The utility model relates to a line fault warning device's of connecting user's ammeter technical field, concretely relates to ammeter RS485 branch line short circuit fault warning device's technique.

Background

With the rapid development of the social and economic level, the continuously rising power demand promotes the development of the power industry and promotes the comprehensive upgrade of the power grid system. In order to improve the service quality of the power industry and bring better electricity consumption experience for residents, the construction of the smart power grid is also carried out rapidly. At present, in the construction of a smart power grid, a low-voltage centralized meter reading system is more and more mature, and is applied to a plurality of places, so that intelligent remote meter reading is realized, and the meter reading efficiency and the electronization settlement rate are effectively improved. However, the low-voltage meter reading system still has some problems, and RS485 short circuit faults sometimes occur in the meter reading system. When the short circuit fault occurs at the port of the RS485, the communication paralysis of the RS485 area can be caused, no reliable tool can be used for quickly positioning a fault point at present, the fault detection can be carried out only by a binary breakpoint method, the troubleshooting and the processing are required to be carried out for one day or even longer, and the electronic settlement rate and the online rate are seriously influenced. And the RS485 is the name of a cable.

SUMMERY OF THE UTILITY MODEL

In order to overcome the defects of the prior art, the utility model aims to provide an ammeter RS485 branch line short-circuit fault warning device carries out real-time supervision to the branch line condition of connecting the household ammeter, when the short circuit appears, breaks off the main line to warn, the safety of effectual protection main line, and play the effect of carrying out fault indication to the short circuit department, do benefit to the fortune and maintain personnel and discover the fault point fast.

To achieve the purpose, the utility model adopts the following technical proposal:

the utility model provides an ammeter RS485 branch line short circuit fault warning device, includes shell, 220V power cord, its characterized in that: the electric meter RS485 branch line short circuit fault warning device also comprises two paths of relay driving modules, a differential amplifier module, a voltage comparator module, a warning lamp module and a power supply module which are arranged in a shell, wherein the power supply module converts 220V commercial power into 5V stabilized power supply for supplying power, and the electric meter short circuit fault warning device also comprises an RS485 branch line interface, an RS485 trunk line interface, an LED warning lamp and a power supply state LED indicator lamp which are connected with a user electric meter, the RS485 branch line interface is a user electric meter interface, the shell is provided with an LED warning lamp hole and a power supply state LED indicator lamp hole, and is also provided with an RS485 trunk line interface hole, a 220V power supply line hole and an RS485 branch line interface hole, the two paths of relay driving modules comprise two paths of triodes, a relay coil and a relay switch, the relay coil and the relay two paths of switches form a PNP relay, the triodes are triodes and are, the relay coil is used for controlling the opening and closing of a relay double-way switch, the two relays are provided with a first pin and an eighth pin to form a relay coil pin, an emitter of the triode is electrically connected with the eighth pin of the two relays, the first pin is connected with a power ground, the two relays are also provided with a second pin, a third pin, a fourth pin, a fifth pin, a sixth pin and a seventh pin, the fourth pin, the fifth pin and the sixth pin form the first relay, the second pin, the third pin and the fourth pin form the second relay, the fourth pin and the fifth pin of the two relays are disconnected and are not used, the sixth pin and the seventh pin are closed by default, the second pin and the third pin are closed by default, the second pin and the sixth pin are used for connecting an RS485 trunk line interface, and the third pin and the seventh pin are used for connecting an RS485 branch line interface, the output of differential amplifier module is connected with the input of voltage comparator module, and the output of voltage comparator module divide into two the tunnel, all the way with the base of triode is connected, and another way is connected with the warning light module, the 5V power is connected to the collecting electrode of triode, and the input differential signal end and the RS485 branch line interface connection of differential amplifier module, real-time supervision is carried out to ammeter RS485 branch line condition to differential amplifier module and voltage comparator module, when the short circuit appears, drives two way relay disconnection RS485 mainlines to light the LED warning light and warn.

The differential amplifier module comprises a differential amplification processing unit, a single-ended signal isolation output unit and an output single-ended signal zeroing circuit, the output single-ended signal zeroing circuit is in circuit connection with the differential amplification processing unit and is used for outputting direct-current signals to zero, the differential amplification processing unit comprises a third chip, the third chip mainly forms a differential amplifier through an operational amplifier, the third chip is provided with an input differential signal pin and an output signal pin, the input differential signal pin forms an input differential signal end of the differential amplifier module, and the output signal pin forms an output end of the differential amplifier module; the single-ended signal isolation output unit comprises a fifth second chip, the fifth second chip is a voltage follower, the fifth second chip is provided with a positive input end, a negative input end and an output end, the output end of the fifth second chip is connected with the negative input end of the fifth second chip to form an isolated signal output end, the voltage comparator module comprises a sixth chip, a first four resistor and a first three resistor which are connected in series, the sixth chip is a voltage comparator, the sixth chip is provided with a third pin which is a positive input end, a second pin which is a reverse input end and a first pin which is an output end, a series node of the first four resistor and the first three resistor is connected with the second pin of the sixth chip, the node voltage of the series node of the first four resistor and the first three resistor is 1V, and an input differential signal pin of the third chip of the differential amplification processing unit is connected with an RS485 branch line interface, the output signal pin of the third chip of the differential amplification processing unit is connected with the positive input end of the fifth second chip of the single-ended signal isolation output unit through the first and second resistors, the isolated signal output end of the fifth second chip of the single-ended signal isolation output unit is connected with the positive input end of the sixth chip of the voltage comparator module, the output end of the sixth chip is in circuit connection with the PNP triode, the emitting electrode of the PNP triode is connected with the warning light module, the differential amplification processing unit detects two ends of the user electric meter, when no short circuit occurs at the two ends of the user electric meter, the differential amplification processing unit amplifies the voltage at the two ends of the user electric meter to the maximum 3.7V and sends the voltage to the voltage comparator module, when the voltage comparator module detects that the input voltage is greater than the threshold value 1V, outputting a high level, not driving the PNP triode, and not driving the warning lamp module; when the two ends of the user electric meter are short-circuited, the differential amplification processing unit detects the short circuit of the two ends of the user electric meter, the two ends of the differential amplification processing unit are also short-circuited, the differential amplification processing unit directly outputs a low level to the voltage comparator module at the moment, the voltage comparator module outputs a high level when an input voltage threshold value is larger than 1V, and outputs a low level when the input voltage threshold value is smaller than 1V, the voltage comparator module outputs a low level, and the PNP triode drives the warning lamp module to enable the LED warning lamp to light.

The third chip is provided with a second pin and a third pin to form the input differential signal pin, a sixth pin to form the output signal pin, a first pin and an eighth pin to form the amplification signal pin, a seventh resistor is connected in series between the first pin and the eighth pin and used for amplifying output voltage, the seventh resistor is used for adjusting amplification factor, and a fifth pin to form the input reference voltage pin, so that the output of the sixth pin is more accurate.

The differential amplification processing unit further comprises an output single-ended signal zero setting circuit, the output single-ended signal zero setting circuit comprises a fifth chip, the fifth chip is a voltage follower and is used for connecting a fifth pin of the third chip, the positive input end of the fifth chip is connected with an eighth resistor and a ninth resistor, one end of the eighth resistor is connected with a positive voltage, the other end of the eighth resistor is connected with one end of the ninth resistor and is connected with the positive input end of the fifth chip together, the other end of the ninth resistor is connected with a negative voltage, the eighth resistor and the ninth resistor are connected in series with a node which is 0V to form the zero setting device, and the voltage of the fifth pin of the third chip is 0V.

The utility model discloses following beneficial effect has:

based on current market does not have the device that system RS485 short-circuit fault monitored the location instruction is copied to the low pressure collection, can't take place RS485 short-circuit fault disconnection in time and thread connection at the collection system of copying, play the effect of protection thread circuit, the utility model discloses ammeter RS485 branch line short-circuit fault warning device is owing to including two way relay drive module, differential amplifier module, voltage comparator module, warning light module and power module, consequently utilize differential amplifier module and voltage comparator module to carry out real-time supervision to the circuit condition, when the short circuit appears, the drive has two way relay drive module disconnection main lines, and light the warning light and warn, the safety of effectual protection main line, and play the effect of carrying out fault indication to the short circuit department, be favorable to fortune dimension personnel to discover the fault point fast, improve fortune dimension efficiency, promote the enterprise image.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments of the present invention will be briefly described below. It is obvious that the drawings described below are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be obtained from these drawings without inventive effort.

FIG. 1 is a schematic block diagram of a circuit in an RS485 branch line short-circuit fault warning device of the utility model;

fig. 2 is a schematic circuit diagram of the short-circuit fault warning device for the RS485 branch line of the utility model;

fig. 3 is the utility model discloses ammeter RS485 branch line short circuit fault warning device schematic diagram.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments with reference to the accompanying drawings.

Wherein the showings are for the purpose of illustration only and are shown by way of illustration only and not in actual form, and are not to be construed as limiting the present patent; for a better understanding of the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "inner", "outer", etc. are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of description, but it is not indicated or implied that the device or element referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are used only for illustrative purposes and are not to be construed as limiting the present patent, and the specific meaning of the terms will be understood by those skilled in the art according to the specific circumstances.

The utility model discloses ammeter RS485 branch line short circuit fault warning device, as figure 1, which comprises an outer shell 01, 220V power cord 02, still including the RS485 branch line interface that connects the user's ammeter, RS485 trunk line interface 04, LED warning light 05 and power state LED pilot lamp 06, RS485 branch line interface is the user's ammeter interface, it has RS485 branch line 03 to mark in the picture, be used for connecing the user's ammeter, be equipped with LED warning light hole and power state LED pilot lamp hole on the shell 01, still be equipped with RS485 trunk line interface hole, 220V power cord hole and RS485 branch line interface hole.

The utility model discloses ammeter RS485 branch line short circuit fault warning device is still including setting up two way relay drive module, differential amplifier module, voltage comparator module, warning light module and the power module in the shell, and power module truns commercial power 220V into 5V constant voltage power supply. The utility model provides a various controls can adopt single chip microcomputer control module to carry out human-computer interface input control, or utilize single chip microcomputer control module to further simplify control process.

The two-way relay driving module comprises a triode, a relay coil and a relay two-way switch, the relay coil and the relay two-way switch form two-way relays, the triode is a PNP triode and is used for controlling the conduction of a 5V power supply so as to control the power supply switch of the relay two-way switch, the relay coil is used for controlling the opening and closing of the relay two-way switch, the two-way relays are provided with a first pin and an eighth pin to form a relay coil pin, an emitting electrode of the triode is electrically connected with the eighth pin of the two-way relays, the first pin is connected with a power ground, the two-way relays are further provided with a second pin, a third pin, a fourth pin, a fifth pin, a sixth pin and a seventh pin, the fourth pin, the fifth pin and the sixth pin form a first-way relay, the second pin, the third pin and the fourth pin and the fifth pin of the two-way relays, the sixth pin and the seventh pin are in a default closed state, namely a normally closed state, the second pin and the third pin are in a default closed state, namely a normally closed state, the second pin and the sixth pin are used for being connected with an RS485 trunk line interface, and the third pin and the seventh pin are used for being connected with an RS485 branch line interface.

The output of differential amplifier module is connected with the input of voltage comparator module, and the output of voltage comparator module divide into two the tunnel, all the way with the base of triode is connected, and another way is connected with the warning light module, and the 5V power is connected to the collecting electrode of triode, and the input differential signal end and the RS485 branch line interface connection of differential amplifier module, differential amplifier module and voltage comparator module carry out real-time supervision to ammeter RS485 branch line condition, when the short circuit appears, drive two tunnel relay disconnection RS485 trunk lines, and light the LED warning light and warn.

The differential amplifier module comprises a differential amplification processing unit, a single-ended signal isolation output unit and an output single-ended signal zeroing circuit, wherein the output single-ended signal zeroing circuit is in circuit connection with the differential amplification processing unit and is used for outputting direct-current signals to zero; the single-ended signal isolation output unit comprises a fifth second chip, the fifth second chip is a voltage follower, the fifth second chip is provided with a positive input end, a negative input end and an output end, the output end of the fifth second chip is connected with the negative input end of the fifth second chip to form an isolated signal output end, the voltage comparator module comprises a sixth chip, and a first four resistor and a first three resistor which are connected in series, the sixth chip is a voltage comparator, the sixth chip is provided with a third pin which is a positive input end and a second pin which is a reverse input end, the first pin is provided as the output end, a series node of the first four resistor and the first three resistor is connected with the second pin of the sixth chip, and the node voltage of the series node of the first four resistor and the first three resistor is 1V. An input differential signal pin of a third chip of the differential amplification processing unit is connected with an RS485 branch line or an interface thereof, an output signal pin of the third chip of the differential amplification processing unit is connected with a positive input end of a fifth second chip of the single-ended signal isolation output unit through a first resistor and a second resistor, an isolated signal output end of the fifth second chip of the single-ended signal isolation output unit is connected with a positive input end of a sixth chip of the voltage comparator module, an output end of the sixth chip is in circuit connection with a PNP triode, and an emitting electrode of the PNP triode is connected with the warning lamp module. The differential amplification processing unit detects two ends of a user electric meter, when no short circuit exists at the two ends of the user electric meter, voltage is generated, the differential amplification processing unit amplifies the voltage at the two ends of the user electric meter to the maximum 3.7V and sends the voltage to the voltage comparator module, when the voltage comparator module detects that the input voltage is greater than the threshold value 1V, high level is output, the PNP triode is not driven, and the warning lamp module is not driven; when the two ends of the user electric meter are short-circuited, the differential amplification processing unit detects the short circuit of the two ends of the user electric meter, the two ends of the differential amplification processing unit are also short-circuited, the differential amplification processing unit directly outputs a low level to the voltage comparator module at the moment, the voltage comparator module outputs a high level when an input voltage threshold value is larger than 1V, and outputs a low level when the input voltage threshold value is smaller than 1V, the voltage comparator module outputs a low level, and the PNP triode drives the warning lamp module to enable the LED warning lamp to light. The third chip is provided with a second pin and a third pin to form the input differential signal pin, a sixth pin to form the output signal pin, a first pin and an eighth pin to form an amplification signal pin, a seventh resistor is connected in series between the first pin and the eighth pin to amplify output voltage, the seventh resistor is used for adjusting amplification factor, and a fifth pin to form an input reference voltage pin, so that the output of the sixth pin is more accurate.

The differential amplification processing unit further comprises an output single-ended signal zero-setting circuit, the output single-ended signal zero-setting circuit comprises a fifth chip, the fifth chip is a voltage follower and is used for connecting a fifth pin of the third chip, the positive input end of the fifth chip is connected with an eighth resistor and a ninth resistor, one end of the eighth resistor is connected with a positive voltage, the other end of the eighth resistor is connected with one end of the ninth resistor and is connected with the positive input end of the fifth chip together, the other end of the ninth resistor is connected with a negative voltage, the eighth resistor and the ninth resistor are connected in series at a node of 0V to form the zero-setting device, and the voltage of the fifth pin of the third chip is 0V.

As shown in fig. 1, which is a block diagram of circuits of the modules, the differential amplifier module detects two ends of the user meter A, B, when there is no short circuit between two ends of the user meter A, B, the differential amplifier amplifies the voltage between two ends of the user meter A, B to a maximum of 3.7V and sends it to the voltage comparator module, and when the voltage comparator module detects that the input voltage is greater than the threshold value of 1V, the differential amplifier outputs a high level, so that the PNP triode is not driven, and the warning light is not driven. In the figure, a differential amplifier is a core component of a differential amplification processing unit in a differential amplifier module, and a voltage comparator is a core component of a voltage comparator module.

As shown in fig. 2, when the two ends of the user electric meter AB are short-circuited and the differential amplifier module detects the short circuit of the two ends of the user electric meter AB, the two ends of the differential amplifier are also short-circuited, at this time, the differential amplifier directly outputs a low level (-1V-0.5V) to the voltage comparator module, the voltage comparator module outputs a high level when setting an input voltage threshold value greater than 1V and outputs a low level when setting an input voltage threshold value less than 1V, so that the voltage comparator outputs a low level, the voltage comparator outputs a low level and directly enables the PNP triode to drive the two relay contacts, wherein the two relays are closed by default and are opened, thereby achieving the purpose of protecting the trunk line RS485 and simultaneously driving the warning lamp to flash by the PNP triode. The power module gets electricity from the alternating current 220V end of the ammeter and converts the electricity into a direct current 5V power supply, namely the 220V is converted into 5V voltage stabilization as shown in the figure, and the voltage stabilization is used by each module power supply. The figure shows the abbreviation used for the user meter AB, i.e. the user meter AB typeface.

In FIG. 2: + 5V: represents +5V of power; -5V: represents power-5V; GND: representing the power ground.

The following pin numbers are described according to the languages commonly used in the industry, such as pin 1, i.e., the first pin, and pin 2, i.e., the second pin, for space saving, not to be listed; the chip numbers are also described in accordance with the languages customary in the industry, such as U3, i.e., the third chip, and U5.1, i.e., the fifth chip. The user meter interface in the figure is the user meter interface. The user meter is short for the user electric meter.

U3 third chip: the instrument operational amplifier is used for amplifying input differential signals; wherein pin 2, i.e., the second pin, and pin 3, i.e., the third pin, are input differential signal pins, and pin 6, i.e., the sixth pin, is an output signal pin; the pin 1, namely the first pin, and the pin 8, namely the eighth pin, are amplification pins, and the series resistor can amplify output voltage; the pin 5, i.e., the fifth pin, is the input reference voltage pin, so that the pin 6, i.e., the sixth pin, outputs more accurately.

R7 is seventh resistance: the value is 49.9 K.OMEGA./1%, and is connected in series at pin 1 and pin 3 of U3, so that U3 amplifies the output voltage.

R12 is the first diode: the value of 1K Ω reduces the signal current output at pin 6 of U3 and reduces interference.

U5 is referred to as the fifth chip: a dual operational amplifier (U5.1, i.e., a fifth first chip, and U5.2, i.e., a fifth second chip); u5.2, namely the fifth chip, forms a voltage follower to enhance the driving capability of the output voltage of the pin 6 of U3 and reduce interference; u5.1, the fifth chip, constitutes pin 5 of the voltage follower connection U3.

R8 eighth resistor, R9 ninth resistor: the value is 1K omega, the serial node of R8 and R9 is 0V and is connected with the pin 5 of U5.1 to form a zero regulator, so that the voltage of the pin 5 of U3 is 0V.

R14, i.e., a first fourth resistor, R13, i.e., a first third resistor: the node voltage of the series connection of R14 and R13 is 1V with the values of 39K omega and 10K omega.

U6 is referred to as the sixth chip: the voltage comparator only uses one voltage comparator U6.1, namely a sixth chip, a pin 3 of the U6.1, namely a third pin of the sixth chip, is a positive phase input end, a pin 2, namely a second pin of the sixth chip, is an inverted phase input end, and the output voltages of the

pins

1 and 2 of the U5.2 are compared; pin 1 of U6.1 is the output terminal; the node voltage of the series connection of R14 and R13 is connected with the inverting input/output end of the pin 2 of U6.1, so that the inverting input end of the pin 2 of U6.1 is 1V; when the voltage of the pin 3 of the U6.1 is greater than the voltage of the pin 2 of the U6.1, the pin 1 of the U6.1 outputs a high level (not less than 1.5V and not more than 3.9V); when the voltage of pin 3 of U6.1 is less than the voltage of pin 2 of U6.1, pin 1 of U6.1 outputs a low level (not more than 3.9V).

R16 is the first sixth resistor; with a value of 4.7K omega, a voltage of 5V is pulled up, keeping transistor Q2 in an off state.

R15 is the first five resistances: a value of 3.6K omega, reduces the effect of the current.

Q2 is PNP triode with model number of 2N3904, and is manufactured by Anson; the function is to control the RELAY2, i.e. the power switch of the two-way RELAY.

RELAY 2: two-way relay, model HFD4/5-S, factory building door macro-switch equipment; pin 1 and pin 8 are relay coils; the pin 4, the pin 5 and the pin 6 are one path of relay, and the pin 2, the pin 3 and the pin 4 are a second path of relay; pins 4 and 5 of the principle diagram are not used; default pins 6 and 7 are closed, and pins 2 and 3 are closed. According to the working principle, when the Q2 triode is switched on, the pin 1 and the pin 8 of the RELAY2 are powered on, then the pin 6 and the pin 7 are disconnected, and the pin 2 and the pin 3 are disconnected, so that the disconnection between the main line and the user electric meter is achieved.

The LED indicates a red light, and the transistor Q2 lights when turned on.

R17 first seventh resistance: the value is 1K Ω, reducing the current.

The utility model discloses accomplish following function: 1) the warning device monitors the short-circuit fault of the RS485 branch line port of the electric meter on line in real time; 2) after the short circuit fault of the RS485 branch line port of the electric meter is monitored, a warning lamp is generated to flash and alarm; 3) and after the short-circuit fault of the RS485 branch line port of the electric meter is monitored, the RS485 fault branch line is disconnected, and the RS485 trunk line is protected.

The utility model discloses can effectually instruct RS485 circuit fault department, not going on the investigation one by one, effectively improve fortune dimension efficiency to when short-circuiting to RS485, can influence the main line, cause the paralysed problem in whole section, done main line protection design, in time cut off when RS485 short-circuiting appears and be connected with the main line, effectively protect other circuit safety, less loss and fortune dimension work load.

It should be noted that the above embodiments are only preferred embodiments of the present invention and the technical principles applied, and any changes or substitutions which can be easily conceived by those skilled in the art within the technical scope of the present invention are also included in the protection scope of the present invention.

Claims

1. The utility model provides an ammeter RS485 branch line short circuit fault warning device, includes shell, 220V power cord, its characterized in that: the electric meter RS485 branch line short circuit fault warning device also comprises two relay driving modules, a differential amplifier module, a voltage comparator module, a warning lamp module and a power supply module which are arranged in the shell, wherein the power supply module converts 220V commercial power into 5V regulated power supply for supplying power, and also comprises an RS485 branch line interface, an RS485 trunk line interface, an LED warning lamp and a power supply state LED indicator lamp which are connected with a user electric meter, the RS485 branch line interface is a user electric meter interface,

the shell is provided with an LED warning lamp hole and a power state LED indicating lamp hole, and is also provided with an RS485 trunk line interface hole, a 220V power line hole and an RS485 branch line interface hole, the two relay driving modules comprise triodes, a relay coil and a relay double-way switch, the relay coil and the relay double-way switch form two relays, the triodes are PNP triodes and are used for controlling the conduction of a 5V power supply so as to control the power switch of the relay double-way switch, the relay coil is used for controlling the disconnection and the closing of the relay double-way switch,

the two relays are provided with a first pin and an eighth pin to form a relay coil pin, the emitter of the triode is electrically connected with the eighth pin of the two relays, the first pin is connected with a power ground, the two relays are also provided with a second pin, a third pin, a fourth pin, a fifth pin, a sixth pin and a seventh pin, the fourth pin, the fifth pin and the sixth pin form the first relay, the second pin, the third pin and the fourth pin form the second relay, the fourth pin and the fifth pin of the two relays are disconnected and are not used, the sixth pin and the seventh pin are closed by default, the second pin and the third pin are closed by default, the second pin and the sixth pin are used for connecting an RS main line interface, and the third pin and the seventh pin are used for connecting an RS485 branch line interface,

the output of differential amplifier module is connected with the input of voltage comparator module, and the output of voltage comparator module divide into two the tunnel, all the way with the base of triode is connected, and another way is connected with the warning light module, the 5V power is connected to the collecting electrode of triode, and the input differential signal end and the RS485 branch line of differential amplifier module are connected, real-time supervision is carried out to ammeter RS485 branch line condition to differential amplifier module and voltage comparator module, when the short circuit appears, drives two way relay disconnection RS485 mainlines to light the LED warning light and warn.

2. The electric meter RS485 branch line short circuit fault warning device of claim 1, wherein: the differential amplifier module comprises a differential amplification processing unit, a single-ended signal isolation output unit and an output single-ended signal zeroing circuit, the output single-ended signal zeroing circuit is in circuit connection with the differential amplification processing unit and is used for outputting direct-current signals to zero, the differential amplification processing unit comprises a third chip, the third chip is a differential amplifier and mainly comprises an operational amplifier, the third chip is provided with an input differential signal pin and an output signal pin, the input differential signal pin forms an input differential signal end of the differential amplifier module, and the output signal pin forms an output end of the differential amplifier module; the single-ended signal isolation output unit comprises a fifth second chip, the fifth second chip is a voltage follower, the fifth second chip is provided with a positive input end, a negative input end and an output end, the output end of the fifth second chip is connected with the negative input end of the fifth second chip to form an isolated signal output end, the voltage comparator module comprises a sixth chip, a first fourth resistor and a first third resistor, the first fourth resistor and the first third resistor are connected in series, the sixth chip is a voltage comparator, the sixth chip is provided with a third pin as a positive input end, a second pin as a reverse input end, the first pin as the output end, the series node of the first fourth resistor and the first third resistor is connected with the second pin of the sixth chip, and the node voltage of the series node of the first fourth resistor and the first third resistor is 1V,

an input differential signal pin of a third chip of the differential amplification processing unit is connected with an RS485 branch line, an output signal pin of the third chip of the differential amplification processing unit is connected with a positive input end of a fifth second chip of the single-ended signal isolation output unit through a first diode and a second resistor, an isolated signal output end of the fifth second chip of the single-ended signal isolation output unit is connected with a positive input end of a sixth chip of the voltage comparator module, an output end of the sixth chip is in circuit connection with a PNP triode, an emitter of the PNP triode is connected with the warning lamp module, the differential amplification processing unit detects two ends of the user electric meter, when no short circuit exists at the two ends of the user electric meter, voltage is generated, the differential amplification processing unit amplifies the voltage at the two ends of the user electric meter to the maximum 3.7V to the voltage comparator module, and when the voltage comparator module detects that the input voltage is greater than a threshold value of 1V, high level is, the PNP triode is not driven, and the warning lamp module is not driven; when the two ends of the user electric meter are short-circuited, the differential amplification processing unit detects the short circuit of the two ends of the user electric meter, the two ends of the differential amplification processing unit are also short-circuited, the differential amplification processing unit directly outputs a low level to the voltage comparator module at the moment, the voltage comparator module outputs a high level when an input voltage threshold value is larger than 1V, and outputs a low level when the input voltage threshold value is smaller than 1V, the voltage comparator module outputs a low level, and the PNP triode drives the warning lamp module to enable the LED warning lamp to light.

3. The electric meter RS485 branch line short circuit fault warning device of claim 2, characterized in that: the third chip is provided with a second pin and a third pin to form the input differential signal pin, a sixth pin to form the output signal pin, a first pin and an eighth pin to form the amplification signal pin, a seventh resistor is connected in series between the first pin and the eighth pin and used for amplifying output voltage, the seventh resistor is used for adjusting amplification factor, and a fifth pin to form the input reference voltage pin, so that the output of the sixth pin is more accurate.