CN209961865U - Electric energy quality monitoring circuit and electric energy monitoring equipment - Google Patents

Abstract

The utility model discloses a power quality monitoring circuit and power monitoring equipment. The power quality monitoring circuit comprises an analog-to-digital conversion circuit and a single-chip processing circuit; the analog-to-digital conversion circuit is connected with the single-chip processing circuit; It detects the voltage analog signal of the power grid, converts the voltage analog signal into a current analog signal, performs analog-to-digital conversion on the current analog signal, and outputs the current digital signal; the single-chip processing circuit is used to process the current digital signal and output the current value. In the utility model, an analog-to-digital conversion circuit and a single-chip processing circuit are set to monitor the power quality of the power grid to be detected. Specifically, the directly connected voltage analog signal is converted into a current analog signal, and then the analog current signal is modulated. digital conversion, so that the current value can be finally obtained, which is more efficient and accurate in power monitoring, and solves the technical problem that power quality cannot be accurately monitored.

Description

Power quality monitoring circuit and power monitoring equipment

technical field

The utility model relates to the technical field of integrated circuits, in particular to a power quality monitoring circuit and a power monitoring device.

Background technique

In view of the fact that power quality affects the safe and economic operation of various enterprises, and, with the development of power grid technology, new development trends have emerged in the composition of modern power grids and loads, and a large number of distributed energy sources (for example, wind power generation and solar power generation, etc. ) access also further deteriorates the power quality.

Specifically, shock loads and nonlinear loads cause serious power quality problems such as waveform distortion, voltage flicker, and voltage sag in the power grid.

On the other hand, the sophisticated and complex electronic equipment that people use also requires the power supply to have the characteristics of high quality and high reliability.

Therefore, continuous monitoring and analysis and evaluation of power quality become particularly important.

However, the traditional mechanical electric energy measuring instrument cannot accurately monitor the power quality in the current grid environment, so the traditional mechanical electric energy measuring instrument has gradually withdrawn from the electric energy monitoring industry.

It can be seen that it is currently impossible to accurately monitor the power quality.

Utility model content

The main purpose of the utility model is to propose a power quality monitoring circuit, which aims to solve the technical problem that the power quality cannot be accurately monitored.

In order to achieve the above purpose, a power quality monitoring circuit proposed by the present utility model includes an analog-to-digital conversion circuit and a single-chip processing circuit; the analog-to-digital conversion circuit is connected with the single-chip processing circuit; wherein,

The analog-to-digital conversion circuit is used to obtain a voltage analog signal of the grid to be detected, convert the voltage analog signal into a current analog signal, perform analog-to-digital conversion on the current analog signal, and output a current digital signal;

The single chip processing circuit is used for processing the current digital signal and outputting the current value.

Preferably, the analog-to-digital conversion circuit includes an analog-to-digital conversion chip and a first resistor;

The first input pin of the analog-to-digital conversion chip is respectively connected to the grid to be detected and the first end of the first resistor, and the second end of the first resistor is connected to the second input pin of the analog-to-digital conversion chip. The output pins of the analog-to-digital conversion chip are connected to the processing circuit of the single-chip microcomputer.

Preferably, the output pins of the analog-to-digital conversion chip are also used to output voltage digital signals;

The single-chip processing circuit is also used for processing the voltage digital signal and outputting a voltage value.

Preferably, the single-chip processing circuit includes a signal processing chip; the analog-to-digital conversion chip is connected to the signal processing chip; wherein,

The first input pin of the signal processing chip is used to obtain the current digital signal;

The output pin of the signal processing chip is used to output the current value.

Preferably, the single-chip processing circuit further includes a first capacitor, a second capacitor and a crystal oscillator;

The oscillation input end of the signal processing chip is respectively connected with the first end of the first capacitor and the first end of the crystal oscillator, and the second end of the crystal oscillator is respectively connected with the first end of the second capacitor and the first end of the crystal oscillator. The oscillation output terminal of the signal processing chip is connected;

The second end of the first capacitor is connected to the second end of the second capacitor, and the second end of the second capacitor is grounded.

Preferably, the power quality monitoring circuit further includes a button circuit; the button circuit includes a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first button, a second button, a third button, and a fourth button and a first internal power supply; wherein,

The first button pin of the signal processing chip is connected to the first end of the second resistor, the second button pin of the signal processing chip is connected to the first end of the third resistor, and the signal processing chip is connected to the first end of the third resistor. The third button pin of the chip is connected to the first end of the fourth resistor, and the fourth button pin of the signal processing chip is connected to the first end of the fifth resistor;

The second end of the second resistor is respectively connected to the second end of the third resistor, the second end of the fourth resistor, the second end of the fifth resistor and the first internal power supply;

The first end of the second resistor is connected to the first end of the first button, and the second end of the first button is grounded;

The first end of the third resistor is connected to the first end of the second button, and the second end of the second button is grounded;

The first end of the fourth resistor is connected to the first end of the third button, and the second end of the third button is grounded;

The first end of the fifth resistor is connected to the first end of the fourth button, and the second end of the fourth button is grounded.

Preferably, the power quality monitoring circuit further includes a power supply unit, and the single-chip processing circuit is connected to the power supply unit; the power supply unit includes an external power supply, a switch, a third capacitor and a fourth capacitor;

The first end of the external power supply is connected to the first end of the switch, the second end of the switch is respectively connected to the first end of the third capacitor and the first end of the fourth capacitor, so The first end of the fourth capacitor is connected to the power input pin of the signal processing chip;

The second end of the external power supply is respectively connected to the second end of the third capacitor and the second end of the fourth capacitor, and the second end of the fourth capacitor is grounded.

Preferably, the power quality monitoring circuit further includes a buzzer alarm circuit, and the single-chip processing circuit is connected to the buzzer alarm circuit; the buzzer alarm circuit includes a sixth resistor, a triode, a buzzer, and a second internal power supply; of which,

The single-chip processing circuit is connected to the first end of the sixth resistor, the second end of the sixth resistor is connected to the base of the triode, and the emitter of the triode is connected to the second internal power supply , the collector of the triode is connected to the first end of the buzzer, and the second end of the buzzer is grounded.

Preferably, the power quality monitoring circuit further includes a light-emitting diode (LED) alarm circuit, and the single-chip processing circuit is connected to the LED alarm circuit; the LED alarm circuit includes a seventh resistor, an LED, and a third internal power supply; wherein,

The single-chip processing circuit is connected to the first end of the seventh resistor, the second end of the seventh resistor is connected to the first end of the LED, and the second end of the LED is connected to the third internal power supply power connection.

The utility model also provides a power monitoring device, the power monitoring device includes the power quality monitoring circuit as described above.

In the utility model, an analog-to-digital conversion circuit and a single-chip processing circuit are set to monitor the power quality of the power grid to be detected. Specifically, the directly connected voltage analog signal is converted into a current analog signal, and then the current analog signal is modulated. digital conversion, so that the current value can be finally obtained, which is more efficient and accurate in power monitoring, and solves the technical problem that power quality cannot be accurately monitored.

Description of drawings

In order to more clearly illustrate the embodiments of the present utility model or the technical solutions in the prior art, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are just some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can also be obtained based on the structures shown in these drawings without any creative effort.

1 is a functional block diagram of an embodiment of a power quality monitoring circuit of the present invention;

FIG. 2 is a schematic diagram of the circuit structure of an embodiment of the power quality monitoring circuit of the present invention.

Description of reference numbers:

The realization, functional characteristics and advantages of the purpose of the present utility model will be further described with reference to the accompanying drawings in conjunction with the embodiments.

Detailed ways

The technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, not all of them. Example. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

It should be noted that if there are directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention, the directional indications are only used to explain a certain posture (such as the accompanying drawings). When the relative positional relationship, movement situation, etc. between the various components shown below), if the specific posture changes, the directional indication also changes accordingly.

In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for the purpose of description, and should not be construed as instructions or Implicit their relative importance or implicitly indicate the number of technical features indicated. Thus, a feature delimited with "first", "second" may expressly or implicitly include at least one of that feature. In addition, the technical solutions between the various embodiments can be combined with each other, but must be based on the realization by those of ordinary skill in the art. When the combination of technical solutions is contradictory or cannot be realized, it should be considered that the combination of such technical solutions does not exist. , is not within the scope of protection required by the present utility model.

The utility model proposes a power quality monitoring circuit, wherein FIG. 1 is a functional block diagram of an embodiment of the power quality monitoring circuit of the present invention, and FIG. 2 is a schematic diagram of the circuit structure of an embodiment of the power quality monitoring circuit of the present invention.

Please refer to FIG. 1 to FIG. 2 in detail, including an analog-to-digital conversion circuit 100 and a single-chip processing circuit 200; the analog-to-digital conversion circuit 100 is connected to the single-chip processing circuit 200; wherein,

The analog-to-digital conversion circuit 100 is configured to obtain a voltage analog signal of the grid to be detected, convert the voltage analog signal into a current analog signal, perform analog-to-digital conversion on the current analog signal, and output a current digital signal;

The single-chip processing circuit 200 is used for processing the current digital signal and outputting a current value.

It can be understood that there are various indicators reflecting the power quality. Taking the current value as an example, the analog-to-digital conversion circuit 100 can be connected to the grid to be detected, and the analog-to-digital conversion circuit 100 will capture the voltage analog signal of the grid to be detected. The voltage analog signal is directly connected, and the current current value of the grid to be detected will be obtained subsequently through the voltage analog signal, so as to complete the monitoring operation of the power quality.

Specifically, considering that the voltage analog signal exists in the form of an analog signal, and considering that the current command type of the power quality index to be obtained is a current value instead of a voltage value, the analog-to-digital conversion circuit 100 may not be able to directly access the recording current value of the current analog signal. Therefore, the voltage analog signal reflecting the voltage value can be directly connected, and then the voltage analog signal can be converted into a current analog signal reflecting the current value. It can be seen that the voltage is converted into a current at this time.

It should be understood that, then, the analog-to-digital conversion circuit 100 may perform analog-to-digital conversion on the current analog signal, that is, convert the analog signal into a digital signal, to obtain a current digital signal corresponding to the current analog signal. This is considering that after converting to a digital signal and then performing related processing, a more accurate indicator value can be obtained. After obtaining the current digital signal, the single-chip processing circuit 200 can obtain the current current value recorded in the current digital signal.

In this embodiment, the analog-to-digital conversion circuit 100 and the single-chip processing circuit 200 will be set to monitor the power quality of the power grid to be detected. Specifically, the directly connected voltage analog signal will be converted into a current analog signal, and then the current analog signal will be The analog-to-digital conversion is performed so that the current value can be finally obtained, which is more efficient and accurate in power monitoring, and solves the technical problem that the power quality cannot be accurately monitored.

Further, the analog-to-digital conversion circuit 100 includes an analog-to-digital conversion chip U1 and a first resistor R1;

The first input pin IN1 of the analog-to-digital conversion chip U1 is respectively connected to the grid to be detected and the first end of the first resistor R1, and the second end of the first resistor R1 is connected to the analog-to-digital conversion chip U1 The second input pin IN2 of the analog-to-digital conversion chip U1 is connected to the output pin OUT1 of the analog-to-digital conversion chip U1 and the single-chip processing circuit 200 is connected.

It can be understood that, considering that the analog-to-digital conversion circuit 100 may not be able to directly access the current analog signal for recording the current value, the voltage analog signal for recording the voltage value may be connected first. For example, if the analog-to-digital conversion circuit 100 includes an analog-to-digital (A/D) chip, the A/D chip may also be called an A/D converter, and the A/D converter may not be able to access current , for example, the first input pin IN1 and the second input pin IN2 of the A/D converter may not be directly connected to the current analog signal of the recorded current value, but can only be directly connected to the voltage analog signal of the recorded voltage value, then A first resistor R1 can be additionally introduced to monitor the current.

Specifically, by connecting a resistor in series, the current to be monitored can be converted into a voltage first, where the current-to-voltage conversion is realized by the resistor. The A/D converter is then connected to the directly accessible voltage. For example, a voltage analog signal will be directly connected to the first input pin IN1 of U1, and a voltage analog signal will be directly connected to the second input pin IN2 of U1. For another voltage analog signal, since the resistance of the first resistor R1 is fixed, the voltage can be converted into a current, thereby realizing the conversion from voltage to current, and completing the monitoring of the current.

It can be seen that in this embodiment, the monitoring of the current is completed on the premise that the A/D converter can only be directly connected to the voltage.

Further, the output pin OUT1 of the analog-to-digital conversion chip U1 is also used to output a voltage digital signal;

The single-chip processing circuit 200 is further configured to process the voltage digital signal and output a voltage value.

It should be understood that, since the voltage analog signal can be directly connected to the first input pin IN1 of the A/D converter in this embodiment, if the current command type of the power quality indicator to be obtained is a voltage value, it can be directly The analog-to-digital conversion of the voltage analog signal will obtain the corresponding voltage digital signal, and finally obtain the voltage value represented by the voltage digital signal.

Further, the single-chip processing circuit 200 includes a signal processing chip U2; the analog-to-digital conversion chip U1 is connected to the signal processing chip U2; wherein,

The first input pin IN of the signal processing chip U2 is used to obtain the current digital signal;

The output pin OUT of the signal processing chip U2 is used to output the current value.

It can be understood that the single-chip processing circuit 200 will include a signal processing chip U2, the chip type of the signal processing chip U2 may be AT89C51, and the signal processing chip U2 of the AT89C51 type is mainly composed of an 8-bit microcontroller. The output pin OUT1 of the analog-to-digital conversion chip U1 is connected to the first input pin IN of the signal processing chip U2, and the output pin OUT1 of the analog-to-digital conversion chip U1 outputs a current digital signal to the first input pin of the signal processing chip U2 IN, the current digital signal is processed by the signal processing chip U2 to obtain the actual current value.

Further, the single-chip processing circuit 200 further includes a first capacitor C1, a second capacitor C2 and a crystal oscillator Y;

The oscillation input terminal X1 of the signal processing chip U2 is respectively connected to the first terminal of the first capacitor C1 and the first terminal of the crystal oscillator Y, and the second terminal of the crystal oscillator Y is respectively connected to the second capacitor C2 The first end of the signal processing chip U2 is connected to the oscillation output end X2;

The second end of the first capacitor C1 is connected to the second end of the second capacitor C2, and the second end of the second capacitor C2 is grounded.

In a specific implementation, a crystal oscillator Y can be set for the signal processing chip U2 to provide a clock signal. Specifically, when the crystal oscillator works, a certain clock frequency will be generated, so that the single-chip processing circuit 200 can operate normally and in an orderly manner. .

The resistance value of the first capacitor C1 is 22F, the resistance value of the second capacitor C2 is 22F, and the oscillation frequency of the crystal oscillator Y is 11.0592MHz.

Further, the power quality monitoring circuit further includes a button circuit 300; the button circuit 300 includes a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a first button KEY1, and a second button KEY2 , the third button KEY3, the fourth button KEY4 and the first internal power supply VCC1; among them,

The first button pin K1 of the signal processing chip U2 is connected to the first end of the second resistor R2, and the second button pin K2 of the signal processing chip U2 is connected to the first end of the third resistor R3 connected, the third button pin K3 of the signal processing chip U2 is connected to the first end of the fourth resistor R4, and the fourth button pin K4 of the signal processing chip U2 is connected to the first end of the fifth resistor R5. one end connection;

The second end of the second resistor R2 is respectively connected with the second end of the third resistor R3, the second end of the fourth resistor R4, the second end of the fifth resistor R5 and the first inner Power supply VCC1 connection;

The first end of the second resistor R2 is connected to the first end of the first key KEY1, and the second end of the first key KEY1 is grounded;

The first end of the third resistor R3 is connected to the first end of the second key KEY2, and the second end of the second key KEY2 is grounded;

The first end of the fourth resistor R4 is connected to the first end of the third button KEY3, and the second end of the third button KEY3 is grounded;

The first end of the fifth resistor R5 is connected to the first end of the fourth key KEY4, and the second end of the fourth key KEY4 is grounded.

It should be understood that a key circuit 300 may be additionally introduced, and the key circuit 300 is composed of four keys for a start button, a reset button, an increase button and a minimize button. The resistance values of the second resistor R2 to the fifth resistor R5 are 4.7K ohms.

First, the first key from top to bottom, that is, the first key KEY1 is the start button, which is used to start the measurement, that is to say, after setting the measurement range, press the first key KEY1 to enter the measurement mode; the second key KEY2 It is the reset button. When the switch S is pressed, it will automatically return to the original starting state. If there is a display screen connected to the single-chip processing circuit 200, the current value or voltage value on the display screen will return to 0; The third button KEY3 and the fourth button KEY4 are the increase button and the minimize button respectively, which can increase and decrease the measurement range. The current value or voltage value obtained by monitoring will fall within this measurement range.

Further, the power quality monitoring circuit further includes a power supply unit 400, and the single-chip processing circuit 200 is connected to the power supply unit 400; the power supply unit 400 includes an external power supply, a switch S, a third capacitor C3 and a fourth capacitor C4;

The first end of the external power supply is connected to the first end of the switch S, and the second end of the switch S is respectively connected to the first end of the third capacitor C3 and the first end of the fourth capacitor C4. The first end of the fourth capacitor C4 is connected to the power input pin X3 of the signal processing chip U2;

The second end of the external power supply is respectively connected to the second end of the third capacitor C3 and the second end of the fourth capacitor C4, and the second end of the fourth capacitor C4 is grounded.

In specific implementation, the power supply unit 400 can be provided to provide stable and reliable power for the operation of the single-chip processing circuit 200, and the switch S can be used to cut off the power supply of the external power supply to the single-chip processing circuit 200 at any time. The capacitance value of the third capacitor C3 is 104F; the capacitance value of the fourth capacitor C4 is 47μF, and the fourth capacitor C4 is a polar capacitor, the first end of the fourth capacitor C4 is the positive electrode, and the second end is the negative electrode.

In addition, a power indicator light can also be set to remind whether the power supply is normal. Specifically, the power input pin X3 of the signal processing chip U2 can be connected to the positive pole of the power indicator light, and the negative pole of the power indicator light can be connected to the first of the power indicator resistor. terminal is connected, and the second terminal of the power indicating resistor is grounded. Among them, the resistance value of the power indicating resistor is 10K ohms.

Further, the power quality monitoring circuit also includes a buzzer alarm circuit 501, and the single-chip processing circuit 200 is connected to the buzzer alarm circuit 501; the buzzer alarm circuit 501 includes a sixth resistor R6, a transistor M, a buzzer The buzzer L and the second internal power supply VCC2; wherein,

The buzzer alarm pin SPEAK of the single-chip processing circuit 200 is connected to the first end of the sixth resistor R6, and the second end of the sixth resistor R6 is connected to the base of the triode M, and the triode M The emitter of M is connected to the second internal power supply VCC2, the collector of the transistor M is connected to the first end of the buzzer L, and the second end of the buzzer L is grounded.

In the specific implementation, a buzzer alarm method can be added. For example, when the voltage value is greater than or equal to 5V, the buzzer L can make a sound to alarm, so as to attract the attention of the staff and prompt the operator to find the problem in time , and properly handle dangerous situations to ensure circuit safety. The resistance value of the sixth resistor R6 is 100 ohms.

Further, the power quality monitoring circuit also includes a light-emitting diode LED alarm circuit 502, and the single-chip processing circuit 200 is connected to the LED alarm circuit 502; the LED alarm circuit 502 includes a seventh resistor R7, an LED, and a third internal Power supply VCC3; among them,

The light-emitting alarm pin X4 of the single-chip processing circuit 2 is connected to the first end of the seventh resistor R7, the second end of the seventh resistor R7 is connected to the first end of the LED, and the first end of the LED is connected. The two terminals are connected to the third internal power supply VCC3.

In a specific implementation, a light emitting diode (Light Emitting Diode, LED) alarm mode can be added. For example, when the voltage value is greater than or equal to 5V, the LED can be made to flash to remind the operator. Wherein, the resistance value of the seventh resistor R7 is 1K ohm; moreover, the first end of the LED is a negative electrode, and the second end of the LED is a positive electrode.

Further, the power quality monitoring circuit further includes a liquid crystal display circuit, and the single-chip processing circuit 200 is connected to the liquid crystal display circuit.

It can be understood that the liquid crystal display circuit may include a liquid crystal display (Liquid Crystal Display, LCD), and the current value or the voltage value may be displayed through the liquid crystal display.

In the specific implementation, the LCD1602 can be used as the model of the liquid crystal display, which is simple and fast to operate and more convenient to use.

The utility model also proposes a power monitoring device, the electronic device includes the above-mentioned power quality monitoring circuit, the specific structure of the power quality monitoring circuit refers to the above-mentioned embodiment, because the power monitoring device adopts all the technical solutions of the above-mentioned embodiments, Therefore, there are at least all the beneficial effects brought about by the technical solutions of the above embodiments, which are not repeated here.

The electronic device may be a hand-held power quality monitor.

The above are only preferred embodiments of the present utility model, and are not intended to limit the scope of the present utility model patent. Under the concept of the utility model of the present utility model, the equivalent structure transformations made by using the contents of the present utility model description and accompanying drawings, Or directly/indirectly applied in other related technical fields are included in the scope of patent protection of the present invention.

Claims (10)

1. A power quality monitoring circuit is characterized by comprising an analog-to-digital conversion circuit and a single chip microcomputer processing circuit; the analog-to-digital conversion circuit is connected with the single chip microcomputer processing circuit; wherein,

the analog-to-digital conversion circuit is used for acquiring a voltage analog signal of a power grid to be detected, converting the voltage analog signal into a current analog signal, performing analog-to-digital conversion on the current analog signal and outputting a current digital signal;

and the singlechip processing circuit is used for processing the current digital signal and outputting a current value.

2. The power quality monitoring circuit of claim 1, wherein the analog-to-digital conversion circuit comprises an analog-to-digital conversion chip and a first resistor;

the first input pin of the analog-to-digital conversion chip is respectively connected with a power grid to be detected and the first end of the first resistor, the second end of the first resistor is connected with the second input pin of the analog-to-digital conversion chip, and the output pin of the analog-to-digital conversion chip is connected with the single chip microcomputer processing circuit.

3. The power quality monitoring circuit according to claim 2, wherein the output pin of the analog-to-digital conversion chip is further configured to output a voltage digital signal;

the singlechip processing circuit is also used for processing the voltage digital signal and outputting a voltage value.

4. The power quality monitoring circuit of claim 2, wherein the single-chip processing circuit comprises a signal processing chip; the analog-to-digital conversion chip is connected with the signal processing chip; wherein,

the first input pin of the signal processing chip is used for acquiring the current digital signal;

and the output pin of the signal processing chip is used for outputting the current value.

5. The power quality monitoring circuit according to claim 4, wherein the single chip processing circuit further comprises a first capacitor, a second capacitor and a crystal oscillator;

the oscillation input end of the signal processing chip is respectively connected with the first end of the first capacitor and the first end of the crystal oscillator, and the second end of the crystal oscillator is respectively connected with the first end of the second capacitor and the oscillation output end of the signal processing chip;

and the second end of the first capacitor is connected with the second end of the second capacitor, and the second end of the second capacitor is grounded.

6. The power quality monitoring circuit of claim 4, wherein the power quality monitoring circuit further comprises a key circuit; the key circuit comprises a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first key, a second key, a third key, a fourth key and a first internal power supply; wherein,

a first key pin of the signal processing chip is connected with a first end of the second resistor, a second key pin of the signal processing chip is connected with a first end of the third resistor, a third key pin of the signal processing chip is connected with a first end of the fourth resistor, and a fourth key pin of the signal processing chip is connected with a first end of the fifth resistor;

a second end of the second resistor is connected with a second end of the third resistor, a second end of the fourth resistor, a second end of the fifth resistor and the first internal power supply respectively;

the first end of the second resistor is connected with the first end of the first key, and the second end of the first key is grounded;

the first end of the third resistor is connected with the first end of the second key, and the second end of the second key is grounded;

the first end of the fourth resistor is connected with the first end of the third key, and the second end of the third key is grounded;

and the first end of the fifth resistor is connected with the first end of the fourth key, and the second end of the fourth key is grounded.

7. The power quality monitoring circuit according to claim 4, wherein the power quality monitoring circuit further comprises a power supply unit, the single chip processing circuit being connected to the power supply unit; the power supply unit comprises an external power supply, a switch, a third capacitor and a fourth capacitor;

a first end of the external power supply is connected with a first end of the switch, a second end of the switch is respectively connected with a first end of the third capacitor and a first end of the fourth capacitor, and a first end of the fourth capacitor is connected with a power input pin of the signal processing chip;

and the second end of the external power supply is respectively connected with the second end of the third capacitor and the second end of the fourth capacitor, and the second end of the fourth capacitor is grounded.

8. The power quality monitoring circuit according to claim 1, wherein the power quality monitoring circuit further comprises a buzzer alarm circuit, and the single chip processing circuit is connected with the buzzer alarm circuit; the buzzing alarm circuit comprises a sixth resistor, a triode, a buzzer and a second internal power supply; wherein,

the single chip microcomputer processing circuit is connected with the first end of the sixth resistor, the second end of the sixth resistor is connected with the base electrode of the triode, the emitting electrode of the triode is connected with the second internal power supply source, the collecting electrode of the triode is connected with the first end of the buzzer, and the second end of the buzzer is grounded.

9. The power quality monitoring circuit according to claim 1, wherein the power quality monitoring circuit further comprises a Light Emitting Diode (LED) alarm circuit, and the single chip processing circuit is connected with the LED alarm circuit; the LED alarm circuit comprises a seventh resistor, an LED and a third internal power supply; wherein,

the single chip microcomputer processing circuit is connected with a first end of the seventh resistor, a second end of the seventh resistor is connected with a first end of the LED, and a second end of the LED is connected with the third internal power supply.

10. A power monitoring device characterized by comprising a power quality monitoring circuit according to any one of claims 1 to 9.

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