阅读说明：本技术 一种无源接地电阻测量仪 (Passive ground resistance measuring apparatu ) 是由 齐兴华 李睿 向旻 安然 于 2020-12-15 设计创作，主要内容包括：本发明公开了一种无源接地电阻测量仪,包括呈长方体状的壳体,壳体的一面上设置有USB接口、第一开关和显示屏,壳体的另一面上设置有第二开关,壳体的一面和另一面相邻,壳体一面和另一面的同一相邻面上设置有第一测量线、第二测量线和第三测量线；壳体内部设置有电池,其用于为无源接地电阻测量仪供电；本发明构建的电路工作电压低,使用安全性较高,无任何触电风险。本发明结构简单,且采用的电子元器件均为常见的电子元器件,成本较低,便于应用推广,具备较广的应用前景。本发明耗电量小,节能省电,操作简单,可长时间使用,避免了测量中因操作不准确所带来的测量误差。(The invention discloses a passive grounding resistance measuring instrument, which comprises a cuboid-shaped shell, wherein one surface of the shell is provided with a USB interface, a first switch and a display screen, the other surface of the shell is provided with a second switch, one surface of the shell is adjacent to the other surface of the shell, and the same adjacent surface of one surface of the shell and the other surface of the shell is provided with a first measuring line, a second measuring line and a third measuring line; a battery is arranged in the shell and used for supplying power to the passive grounding resistance measuring instrument; the circuit constructed by the invention has low working voltage, higher use safety and no electric shock risk. The invention has simple structure, adopts common electronic components, has lower cost, is convenient for application and popularization and has wider application prospect. The invention has the advantages of low power consumption, energy and power saving, simple operation and long-time use, and avoids the measurement error caused by inaccurate operation in measurement.)

1. A passive grounding resistance measuring instrument is characterized by comprising a cuboid-shaped shell, wherein one surface of the shell is provided with a USB interface (1), a first switch (2) and a display screen (3), the other surface of the shell is provided with a second switch (8), one surface of the shell is adjacent to the other surface of the shell, and the same adjacent surface of one surface of the shell and the other surface of the shell is provided with a first measuring line (6), a second measuring line (5) and a third measuring line (4); a battery (7) is arranged in the shell and used for supplying power to the passive grounding resistance measuring instrument;

the passive grounding resistance measuring instrument also comprises a control circuit, a display circuit, a power supply circuit, a downloading circuit, a voltage and current detection circuit, a detection power supply circuit and a measuring circuit;

the power supply circuit is respectively connected with the display circuit, the download circuit, the voltage and current detection circuit, the detection power supply circuit and the measurement circuit, the control circuit is respectively connected with the display circuit, the download circuit, the voltage and current detection circuit and the measurement circuit, and the voltage and current detection circuit is respectively connected with the detection power supply circuit and the measurement circuit.

2. The passive ground resistance measuring instrument according to claim 1, wherein the control circuit comprises a control chip U1 with model number STC8A8K64S4A12_ LQFP64, and a GND pin of the control chip U1 is grounded.

3. The passive ground resistance measuring instrument according to claim 2, wherein the display circuit comprises a display screen OLED1 with model number ZJY096S0700WG01, a GND pin of the display screen OLED1 is grounded, a VCC pin of the display screen OLED1 is connected with one end of a switch S4 in the power supply circuit, and a D0 pin, a D1 pin, a RES pin, a DC pin and a CS pin of the display screen OLED1 are respectively connected with a P1.2-P1.6 pin of the control chip U1 in a one-to-one correspondence manner.

4. The passive ground resistance measuring instrument according to claim 3, wherein the power circuit comprises a connection terminal JP1, the 1 st pin of the connection terminal JP1 is connected with the positive electrode of the 5V battery and the other end of the switch S4, respectively, the 2 nd pin of the connection terminal JP1 is connected with the negative electrode of the 5V battery and is grounded; one end of the switch S4 is connected with the anode of the LED D1 through the resistor R2, and the cathode of the LED D1 is grounded.

5. The passive ground resistance measuring instrument according to claim 4, wherein the download circuit comprises a USB interface J1, a single chip microcomputer U2 with model STC15F104E and a switching chip U3 with model CH 340G;

a1 st pin of the USB interface J1 is connected to one end of a switch S4, a2 nd pin of the USB interface J1 is connected to a D-pin of a switch U3, a 5 th pin of the USB interface J1 is grounded, a P3.2 pin of the single chip microcomputer U2 is connected to one end of a switch S2, the other end of the switch S2 is grounded, a P3.3 pin of the single chip microcomputer U2 is connected to an RXD pin of a control chip U1, a GND pin of the single chip microcomputer U2 is grounded, a VCC pin of the single chip microcomputer U2 is connected to one ends of a grounded capacitor C1, a grounded capacitor C2 and a switch S4, a P3.4 pin of the single chip microcomputer U2 is connected to a base of a triode Q1 through a resistor R4, an emitter of the triode Q1 is connected to one end of a switch S4, and a collector of the triode Q1 is connected to a VCC pin of the control chip U1;

the VCC pin of the switching chip U3 is connected with one end of a switch S4, the XO pin of the switching chip U3 is connected with one end of a grounding capacitor C4 and one end of a crystal oscillator Y1 respectively, the XI pin of the switching chip U3 is connected with the other ends of a grounding capacitor C3 and a crystal oscillator Y1 respectively, the V3 pin of the switching chip U3 is connected with the grounding capacitor C5, the RXD pin of the switching chip U3 is connected with the TXD pin of the control chip U1 through a resistor R5, the TXD pin of the switching chip U3 is connected with the cathode of a diode D2, the anode of the diode D2 is connected with the RXD pin of the control chip U1, and the GND pin of the switching chip U3 is grounded.

6. The passive ground resistance measuring instrument according to claim 5, wherein the voltage current detection circuit comprises a switch S1, a current detection chip U4 with model AD620 and a voltage detection chip U5 with model ADS 1256;

one end of the switch S1 is grounded, the other end of the switch S1 is connected with the P1.7 pin of the control chip through a resistor R1, the S + pin of the current detection chip U4 is connected to the AIN0 pin of the voltage detection chip U5 and the anode of the ground electric field, the S-pin of the current detection chip U4 is connected to one end of a resistor R3 and a first fixed end of a sliding resistor RP1, the VO + pin of the current detection chip U4 is connected to the AIN2 pin of the voltage detection chip U5, the VO-pin of the current detection chip U4 is connected to the AIN3 pin of the voltage detection chip U5, the GND pin of the current detection chip U4 is connected with the 2 nd pin of the connection terminal JP2 in the detection power supply circuit, the V + pin of the current detection chip U4 is connected with the 3 rd pin of a connection terminal JP2 in a detection power supply circuit, the V-pin of the current detection chip U4 is connected with the 1 st pin of a wiring terminal JP2 in the detection power supply circuit;

the pin 5V of the voltage detection chip U5 is connected with one end of a switch S4, the GND pin of the voltage detection chip U5 is grounded, the SCLK pin, the DIN pin, the DOUT pin, the DRDY pin and the CS pin of the voltage detection chip U5 are respectively connected with the P2.0-P2.4 pins of the control chip U1 in a one-to-one correspondence manner, the AIN1 pin of the voltage detection chip U5 is respectively connected with the negative electrode of a geoelectric field, the other end of a resistor R3 and one end of the switch S3, and the other end of the switch S3 is respectively connected with the sliding end and the second fixed end of the sliding resistor RP 1.

7. The passive ground resistance measuring instrument according to claim 6, wherein the detection power supply circuit comprises a connection terminal JP2 and a voltage stabilization chip U8 with model XL6009, a1 st pin of the connection terminal JP2 is respectively connected with one end of a capacitor C7, a cathode of a polar capacitor E3 and one end of a resistor R9, a2 nd pin of the connection terminal JP2 is respectively connected with an anode of a polar capacitor E3 and a cathode of a polar capacitor E1, a 3 rd pin of the connection terminal JP2 is respectively connected with one end of a capacitor C6, an anode of a polar capacitor E1, one end of a resistor R6 and a 24V power supply, the other end of a capacitor C6 and the other end of a capacitor C7, the other end of the resistor R6 is respectively connected with a positive input terminal of a chip IC1 with model TDA2030, a cathode of a polar capacitor E2 and the other end of a resistor R9, a positive electrode of a polar capacitor E2 is connected with one end of a resistor R7, the other end of the resistor R7 is respectively connected with the inverting input end of a chip IC1 and a grounding resistor R8, the 5 th pin of the chip IC1 is connected with a 24V power supply, the 3 rd pin of the chip IC1 is grounded, and the output end of the chip IC1 is grounded;

the VIN pin of the voltage stabilizing chip U8 is respectively connected with one end of a switch S4, the anode of a diode D4, the anode of a polar capacitor C9, a grounding capacitor C11 and one end of an inductor T2 with an iron core, the SW pin of the regulator chip U8 is connected to the other end of the inductor T2 and one end of the capacitor C8, the FB pin of the voltage stabilizing chip U8 is respectively connected with one end of a grounding resistor R12 and one end of a resistor R13, the other end of the capacitor C8 is respectively connected with one end of the inductance T1 with iron core and the anode of the diode D3, the cathode of the diode D3 is respectively connected with the other end of the resistor R13, the anode of the polar capacitor C10, the grounding capacitor C12 and one end of the inductance T3 with the iron core, the other end of the inductor T3 is connected with a grounding capacitor C13, and the other end of the inductor T1, the anode of the diode D4, the cathode of the polar capacitor C9, the GND pin of the voltage stabilizing chip U8 and the cathode of the polar capacitor C10 are all grounded.

8. The passive ground resistance measuring instrument according to claim 7, wherein the measuring circuit comprises a connection terminal JP3, the 1 st pin of the connection terminal JP3 is grounded and connected with the normally closed contact of a 5-pin relay U7 of 5V working voltage, the 2 nd pin of the connection terminal JP3 is connected with the normally closed contact of a 5-pin relay U6 of 5V working voltage and the normally open contact of a relay U7 respectively, the 3 rd pin of the connection terminal JP3 is connected with the normally open contact of a relay U6, the switch end of the relay U6 is connected with the AIN1 pin of a voltage detecting chip U5, one end of the coil in the relay U6 is grounded, the other end of the coil in the relay U6 is connected with the emitter of an NPN type triode Q2, the base of the triode Q2 is connected with the P0.1 pin of a control chip U1 through a resistor R10, the collector of the triode Q2 is connected with one end of a switch S4, the switch end of the relay U7 is connected with an AIN0 pin of a voltage detection chip U5, one end of a coil in the relay U7 is grounded, the other end of the coil in the relay U7 is connected with an emitter of an NPN type triode Q3, a base electrode of the triode Q3 is connected with a P0.0 pin of the control chip U1 through a resistor R11, and a collector electrode of the triode Q3 is connected with one end of a switch S4.

9. The passive ground resistance measuring instrument according to claim 8, wherein the USB interface J1 is used as a USB interface (1), the display screen OLED1 is used as a display screen (3), the switch S3 is used as a first switch (2), the switch S4 is used as a second switch (8), the 1 st pin of the connection terminal JP3 leads out a first measuring line (6), the 2 nd pin of the connection terminal JP3 leads out a second measuring line (5), and the 3 rd pin of the connection terminal JP3 leads out a third measuring line (4).

Technical Field

The invention belongs to the technical field of electronics, and particularly relates to a passive grounding resistance measuring instrument.

Background

The grounding resistance is an important parameter for measuring whether the grounding state is good or not, and is the resistance encountered by the current flowing from the grounding device to the ground and then flowing to another grounding body through the ground or spreading to a remote place, and comprises the resistances of the grounding wire and the grounding body, the contact resistance between the grounding body and the ground, the resistance of the ground between the two grounding bodies or the resistance of the ground from the grounding body to the infinite place. The size of the grounding resistance directly reflects the good degree of the contact between the electric device and the ground, and also reflects the scale of the grounding grid. However, the existing ground resistance measurement technology has the following disadvantages:

1. the labor and time are wasted due to the fact that the labor is needed to do work to generate electricity, and the labor cost is increased.

2. The manual power generation can not well control the shaking speed, frequency and stability.

3. The transmitting voltage is higher, and actual measurement reaches more than 90V, has construction safety hidden danger, has the risk that causes bodily injury.

4. Not only the measurement system needs to supply power, but also needs a battery to supply power to the ground, so that the energy consumption is high, and the long-term work is not facilitated.

5. When the device is used outside, a standby power supply is required, the power supply voltage is constantly noticed, and the device is replaced in time.

Disclosure of Invention

Aiming at the defects in the prior art, the passive grounding resistance measuring instrument provided by the invention solves the problems in the prior art.

In order to achieve the purpose of the invention, the invention adopts the technical scheme that: a passive grounding resistance measuring instrument comprises a cuboid-shaped shell, wherein a USB interface, a first switch and a display screen are arranged on one surface of the shell, a second switch is arranged on the other surface of the shell, one surface of the shell is adjacent to the other surface of the shell, and a first measuring line, a second measuring line and a third measuring line are arranged on the same adjacent surface of one surface of the shell and the other surface of the shell; a battery is arranged in the shell and used for supplying power to the passive grounding resistance measuring instrument;

the passive grounding resistance measuring instrument also comprises a control circuit, a display circuit, a power supply circuit, a downloading circuit, a voltage and current detection circuit, a detection power supply circuit and a measuring circuit;

the power supply circuit is respectively connected with the display circuit, the download circuit, the voltage and current detection circuit, the detection power supply circuit and the measurement circuit, the control circuit is respectively connected with the display circuit, the download circuit, the voltage and current detection circuit and the measurement circuit, and the voltage and current detection circuit is respectively connected with the detection power supply circuit and the measurement circuit.

Further, the control circuit comprises a control chip U1 with the model of STC8A8K64S4A12_ LQFP64, and a GND pin of the control chip U1 is grounded.

Further, the display circuit comprises a display screen OLED1 with the model number ZJY096S0700WG01, a GND pin of the display screen OLED1 is grounded, a VCC pin of the display screen OLED1 is connected with one end of a switch S4 in the power supply circuit, and a D0 pin, a D1 pin, a RES pin, a DC pin and a CS pin of the display screen OLED1 are respectively connected with P1.2-P1.6 pins of the control chip U1 in a one-to-one correspondence mode.

Further, the power supply circuit comprises a connection terminal JP1, wherein the 1 st pin of the connection terminal JP1 is respectively connected with the anode of the 5V battery and the other end of the switch S4, and the 2 nd pin of the connection terminal JP1 is connected with the cathode of the 5V battery and is grounded; one end of the switch S4 is connected with the anode of the LED D1 through the resistor R2, and the cathode of the LED D1 is grounded.

Further, the download circuit comprises a USB interface J1, a singlechip U2 with the model of STC15F104E and a switching chip U3 with the model of CH 340G;

a1 st pin of the USB interface J1 is connected to one end of a switch S4, a2 nd pin of the USB interface J1 is connected to a D-pin of a switch U3, a 5 th pin of the USB interface J1 is grounded, a P3.2 pin of the single chip microcomputer U2 is connected to one end of a switch S2, the other end of the switch S2 is grounded, a P3.3 pin of the single chip microcomputer U2 is connected to an RXD pin of a control chip U1, a GND pin of the single chip microcomputer U2 is grounded, a VCC pin of the single chip microcomputer U2 is connected to one ends of a grounded capacitor C1, a grounded capacitor C2 and a switch S4, a P3.4 pin of the single chip microcomputer U2 is connected to a base of a triode Q1 through a resistor R4, an emitter of the triode Q1 is connected to one end of a switch S4, and a collector of the triode Q1 is connected to a VCC pin of the control chip U1;

the VCC pin of the switching chip U3 is connected with one end of a switch S4, the XO pin of the switching chip U3 is connected with one end of a grounding capacitor C4 and one end of a crystal oscillator Y1 respectively, the XI pin of the switching chip U3 is connected with the other ends of a grounding capacitor C3 and a crystal oscillator Y1 respectively, the V3 pin of the switching chip U3 is connected with the grounding capacitor C5, the RXD pin of the switching chip U3 is connected with the TXD pin of the control chip U1 through a resistor R5, the TXD pin of the switching chip U3 is connected with the cathode of a diode D2, the anode of the diode D2 is connected with the RXD pin of the control chip U1, and the GND pin of the switching chip U3 is grounded.

Further, the voltage and current detection circuit comprises a switch S1, a current detection chip U4 with the model number AD620 and a voltage detection chip U5 with the model number ADS 1256;

one end of the switch S1 is grounded, the other end of the switch S1 is connected with the P1.7 pin of the control chip through a resistor R1, the S + pin of the current detection chip U4 is connected to the AIN0 pin of the voltage detection chip U5 and the anode of the ground electric field, the S-pin of the current detection chip U4 is connected to one end of a resistor R3 and a first fixed end of a sliding resistor RP1, the VO + pin of the current detection chip U4 is connected to the AIN2 pin of the voltage detection chip U5, the VO-pin of the current detection chip U4 is connected to the AIN3 pin of the voltage detection chip U5, the GND pin of the current detection chip U4 is connected with the 2 nd pin of the connection terminal JP2 in the detection power supply circuit, the V + pin of the current detection chip U4 is connected with the 3 rd pin of a connection terminal JP2 in a detection power supply circuit, the V-pin of the current detection chip U4 is connected with the 1 st pin of a wiring terminal JP2 in the detection power supply circuit;

the pin 5V of the voltage detection chip U5 is connected with one end of a switch S4, the GND pin of the voltage detection chip U5 is grounded, the SCLK pin, the DIN pin, the DOUT pin, the DRDY pin and the CS pin of the voltage detection chip U5 are respectively connected with the P2.0-P2.4 pins of the control chip U1 in a one-to-one correspondence manner, the AIN1 pin of the voltage detection chip U5 is respectively connected with the negative electrode of a geoelectric field, the other end of a resistor R3 and one end of the switch S3, and the other end of the switch S3 is respectively connected with the sliding end and the second fixed end of the sliding resistor RP 1.

Further, the detection power supply circuit comprises a connection terminal JP2 and a voltage stabilization chip U8 with model XL6009, wherein a1 st pin of the connection terminal JP2 is respectively connected with one end of a capacitor C7, a cathode of a polar capacitor E3 and one end of a resistor R9, a2 nd pin of the connection terminal JP2 is respectively connected with an anode of a polar capacitor E3 and a cathode of a polar capacitor E1, a 3 rd pin of the connection terminal JP2 is respectively connected with one end of a capacitor C6, an anode of a polar capacitor E1, one end of a resistor R6 and a 24V power supply, the other end of the capacitor C6 is connected with the other end of a capacitor C7, the other end of the resistor R6 is respectively connected with an input terminal of a chip IC1 with model TDA2030, a cathode of a polar capacitor E2 and the other end of a resistor R9, an anode of the polar capacitor E2 is connected with one end of a resistor R7, and the other end of a resistor R7 is respectively connected with an inverted input terminal of a resistor IC 5953 and an inverted terminal 86, the 5 th pin of the chip IC1 is connected with a 24V power supply, the 3 rd pin of the chip IC1 is grounded, and the output end of the chip IC1 is grounded;

the VIN pin of the voltage stabilizing chip U8 is respectively connected with one end of a switch S4, the anode of a diode D4, the anode of a polar capacitor C9, a grounding capacitor C11 and one end of an inductor T2 with an iron core, the SW pin of the regulator chip U8 is connected to the other end of the inductor T2 and one end of the capacitor C8, the FB pin of the voltage stabilizing chip U8 is respectively connected with one end of a grounding resistor R12 and one end of a resistor R13, the other end of the capacitor C8 is respectively connected with one end of the inductance T1 with iron core and the anode of the diode D3, the cathode of the diode D3 is respectively connected with the other end of the resistor R13, the anode of the polar capacitor C10, the grounding capacitor C12 and one end of the inductance T3 with the iron core, the other end of the inductor T3 is connected with a grounding capacitor C13, and the other end of the inductor T1, the anode of the diode D4, the cathode of the polar capacitor C9, the GND pin of the voltage stabilizing chip U8 and the cathode of the polar capacitor C10 are all grounded.

Further, the measuring circuit includes a connection terminal JP3, the 1 st pin of the connection terminal JP3 is grounded and connected with the normally closed contact of a 5-pin relay U7 of 5V operating voltage, the 2 nd pin of the connection terminal JP3 is connected with the normally closed contact of a 5-pin relay U6 of 5V operating voltage and the normally open contact of a relay U7, respectively, the 3 rd pin of the connection terminal JP3 is connected with the normally open contact of a relay U6, the switch end of the relay U6 is connected with the AIN1 pin of a voltage detection chip U5, one end of the coil in the relay U6 is grounded, the other end of the coil in the relay U6 is connected with the emitter of an NPN type transistor Q2, the base of the transistor Q2 is connected with the P0.1 pin of a control chip U1 through a resistor R10, the collector of the transistor Q2 is connected with one end of a switch S4, the switch end of the relay U7 is connected with the AIN0 pin of the voltage detection chip U5, one end of a coil in the relay U7 is grounded, the other end of the coil in the relay U7 is connected with an emitter of an NPN type triode Q3, a base electrode of the triode Q3 is connected with a P0.0 pin of a control chip U1 through a resistor R11, and a collector electrode of the triode Q3 is connected with one end of a switch S4.

Further, the USB interface J1 serves as a USB interface, the display screen OLED1 serves as a display screen, the switch S3 serves as a first switch, the switch S4 serves as a second switch, the 1 st pin of the connection terminal JP3 leads out a first measurement line, the 2 nd pin of the connection terminal JP3 leads out a second measurement line, and the 3 rd pin of the connection terminal JP3 leads out a third measurement line.

The invention has the beneficial effects that:

(1) the circuit constructed by the invention has low working voltage, higher use safety and no electric shock risk.

(2) The invention has simple structure, adopts common electronic components, has lower cost, is convenient for application and popularization and has wider application prospect.

(3) The invention has simple operation and low use difficulty, and avoids the measurement error caused by inaccurate operation in measurement.

(4) The invention has the advantages of low power consumption, energy and electricity saving and long-term use.

(5) The electronic devices adopted by the invention are small in size, a circuit can be loaded by a small shell, the carrying is convenient, and the mobility is greatly improved.

Drawings

Fig. 1 is a schematic structural diagram of a passive ground resistance measuring instrument according to the present invention;

FIG. 2 is a control circuit diagram of the present invention;

FIG. 3 is a circuit diagram of the present invention;

FIG. 4 is a power supply circuit diagram of the present invention;

FIG. 5 is a circuit diagram of the download circuit of the present invention;

FIG. 6 is a circuit diagram of voltage current detection according to the present invention;

FIG. 7 is a diagram of a power supply detection circuit according to the present invention;

FIG. 8 is a diagram of a measurement circuit according to the present invention;

wherein: 1-USB interface, 2 first switch, 3 display screen, 4 third measuring line, 5 second measuring line, 6-first measuring line, 7-battery, 8-second switch.

Detailed Description

The following description of the embodiments of the present invention is provided to facilitate the understanding of the present invention by those skilled in the art, but it should be understood that the present invention is not limited to the scope of the embodiments, and it will be apparent to those skilled in the art that various changes may be made without departing from the spirit and scope of the invention as defined and defined in the appended claims, and all matters produced by the invention using the inventive concept are protected.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in fig. 1, a passive ground resistance measuring instrument includes a rectangular casing, one side of the casing is provided with a USB interface 1, a first switch 2 and a display screen 3, the other side of the casing is provided with a second switch 8, one side of the casing is adjacent to the other side of the casing, and the same adjacent side of the one side of the casing and the other side is provided with a first measuring line 6, a second measuring line 5 and a third measuring line 4; a battery 7 is arranged inside the casing and is used for supplying power to the passive grounding resistance measuring instrument.

The passive grounding resistance measuring instrument also comprises a control circuit, a display circuit, a power supply circuit, a downloading circuit, a voltage and current detection circuit, a detection power supply circuit and a measuring circuit; the power supply circuit is respectively connected with the display circuit, the download circuit, the voltage and current detection circuit, the detection power supply circuit and the measurement circuit, the control circuit is respectively connected with the display circuit, the download circuit, the voltage and current detection circuit and the measurement circuit, and the voltage and current detection circuit is respectively connected with the detection power supply circuit and the measurement circuit.

As shown in fig. 2, the control circuit includes a control chip U1 with model number STC8A8K64S4a12_ LQFP64, and the GND pin of the control chip U1 is grounded.

As shown in fig. 3, the display circuit includes a display screen OLED1 of model number ZJY096S0700WG01, a GND pin of the display screen OLED1 is grounded, a VCC pin of the display screen OLED1 is connected with one end of a switch S4 in the power supply circuit, and a D0 pin, a D1 pin, a RES pin, a DC pin and a CS pin of the display screen OLED1 are respectively connected with P1.2-P1.6 pins of the control chip U1 in a one-to-one correspondence manner.

As shown in fig. 4, the power supply circuit includes a connection terminal JP1, a1 st pin of the connection terminal JP1 is connected to a positive electrode of the 5V battery and the other end of the switch S4, respectively, and a2 nd pin of the connection terminal JP1 is connected to a negative electrode of the 5V battery and is grounded; one end of the switch S4 is connected to the anode of the led D1 through the resistor R2, and the cathode of the led D1 is grounded.

As shown in fig. 5, the download circuit includes a USB interface J1, a single chip microcomputer U2 with model STC15F104E, and a switching chip U3 with model CH 340G;

the 1 st pin of the USB interface J1 is connected with one end of a switch S4, the 2 nd pin of the USB interface J1 is connected with a D-pin of a switching chip U3, the 5 th pin of the USB interface J1 is grounded, the P3.2 pin of a singlechip U2 is connected with one end of a switch S2, the other end of the switch S2 is grounded, the P3.3 pin of the singlechip U2 is connected with an RXD pin of a control chip U1, the GND pin of the singlechip U2 is grounded, the VCC pin of the singlechip U2 is respectively connected with a grounded capacitor C1, a grounded capacitor C2 and one end of a switch S4, the P3.4 pin of the singlechip U2 is connected with the base of a triode Q1 through a resistor R4, the emitter of the triode Q1 is connected with one end of the switch S4, and the collector of the triode Q1 is connected with the VCC pin of the control.

The VCC pin of the switching chip U3 is connected with one end of the switch S4, the XO pin of the switching chip U3 is connected with one end of a grounding capacitor C4 and one end of a crystal oscillator Y1 respectively, the XI pin of the switching chip U3 is connected with the other end of a grounding capacitor C3 and the other end of a crystal oscillator Y1 respectively, the V3 pin of the switching chip U3 is connected with the grounding capacitor C5, the RXD pin of the switching chip U3 is connected with the TXD pin of the control chip U1 through a resistor R5, the TXD pin of the switching chip U3 is connected with the cathode of the diode D2, the anode of the diode D2 is connected with the D pin of the control chip U1, and the GND pin of the switching chip RXD 3.

As shown in fig. 6, the voltage current detection circuit includes a switch S1, a current detection chip U4 of model AD620, and a voltage detection chip U5 of model ADs 1256; one end of the switch S1 is grounded, the other end of the switch S1 is connected with a P1.7 pin of the control chip through a resistor R1, an S + pin of a current detection chip U4 is respectively connected with an AIN0 pin of a voltage detection chip U5 and the anode of a ground electric field, an S-pin of a current detection chip U4 is respectively connected with one end of the resistor R3 and a first fixed end of a sliding resistor RP1, a VO + pin of a current detection chip U4 is connected with an AIN2 pin of the voltage detection chip U5, a VO-pin of the current detection chip U4 is connected with an AIN3 pin of the voltage detection chip U5, a GND pin of the current detection chip U4 is connected with a2 nd pin of a connection terminal JP2 in a detection power supply circuit, a V + pin of the current detection chip U4 is connected with a 3 rd pin of a connection terminal 2 in the detection power supply circuit, and a V-pin of a U4 is connected with a first connection terminal 2 in the detection power supply circuit.

The pin 5V of the voltage detection chip U5 is connected with one end of the switch S4, the GND pin of the voltage detection chip U5 is grounded, the SCLK pin, the DIN pin, the DOUT pin, the DRDY pin and the CS pin of the voltage detection chip U5 are respectively connected with the pins P2.0-P2.4 of the control chip U1 in a one-to-one correspondence manner, the pin AIN1 of the voltage detection chip U5 is respectively connected with the negative pole of a ground electric field, the other end of the resistor R3 and one end of the switch S3, and the other end of the switch S3 is respectively connected with the sliding end and the second fixed end of the sliding resistor RP 1.

As shown in fig. 7, the detection power supply circuit includes a connection terminal JP2 and a voltage stabilization chip U8 with model XL6009, a1 st pin of the connection terminal JP2 is respectively connected with one end of a capacitor C7, a cathode of a polar capacitor E3 and one end of a resistor R9, a2 nd pin of the connection terminal JP2 is respectively connected with an anode of the polar capacitor E3 and a cathode of a polar capacitor E1, a 3 rd pin of the connection terminal JP2 is respectively connected with one end of a capacitor C6, an anode of a polar capacitor E1, one end of a resistor R6 and a 24V power supply, the other end of a capacitor C6 and the other end of a capacitor C7, the other end of a resistor R6 is respectively connected with a positive input terminal of a chip IC1 with model TDA2030, a cathode of a polar capacitor E2 and the other end of a resistor R9, an anode of a polar capacitor E2 is connected with one end of a resistor R7, the other end of a resistor R7 is respectively connected with an input terminal of a chip IC1 and an inverted resistor R8, and a, pin 3 of chip IC1 is grounded and the output of chip IC1 is grounded.

A VIN pin of the voltage regulation chip U8 is connected to one end of the switch S4, an anode of the diode D4, an anode of the polar capacitor C9, the ground capacitor C11 and one end of the inductor T2 with an iron core, a SW pin of the voltage regulation chip U8 is connected to the other end of the inductor T2 and one end of the capacitor C8, a FB pin of the voltage regulation chip U8 is connected to one ends of the ground resistor R12 and the resistor R13, the other end of the capacitor C8 is connected to one end of the inductor T1 with an iron core and an anode of the diode D3, a cathode of the diode D3 is connected to the other end of the resistor R13, an anode of the polar capacitor C10, a ground capacitor C12 and one end of the inductor T12 with an iron core, the other end of the inductor T12 is connected to the ground capacitor C12, and the other end of the inductor T12, an anode of the diode D12, a cathode of the polar capacitor C12 and a cathode of the capacitor C12 with a GND.

As shown in fig. 8, the measuring circuit includes a connection terminal JP3, a pin 1 of the connection terminal JP3 is grounded and connected with a normally closed contact of a 5-pin relay U7 of 5V operating voltage, a pin 2 of the connection terminal JP3 is connected with a normally closed contact of a 5-pin relay U6 of 5V operating voltage and a normally open contact of a relay U7 respectively, a pin 3 of the connection terminal JP3 is connected with a normally open contact of a relay U6, a switch terminal of a relay U6 is connected with an AIN1 pin of a voltage detection chip U5, one end of a coil in the relay U6 is grounded, the other end of the coil in the relay U6 is connected with an emitter of an NPN-type triode Q2, a base of a triode Q2 is connected with a P0.1 pin of a control chip U5 through a resistor R10, a collector of a triode Q2 is connected with one end of a switch S4, a switch terminal of the relay U7 is connected with an n0 pin of a voltage detection chip U5, one end of the, the other end of the coil in the relay U7 is connected with the emitter of an NPN type triode Q3, the base of the triode Q3 is connected with the P0.0 pin of the control chip U1 through a resistor R11, and the collector of the triode Q3 is connected with one end of a switch S4.

The USB interface J1 is used as a USB interface 1, the display screen OLED1 is used as a display screen 3, the switch S3 is used as a first switch 2, the switch S4 is used as a second switch 8, a first measuring line 6 is led out from a1 st pin of a connecting terminal JP3, a second measuring line 5 is led out from a2 nd pin of a connecting terminal JP3, and a third measuring line 4 is led out from a 3 rd pin of a connecting terminal JP 3.

The invention inserts three electrodes (E, P, C) into the ground, but without need of power supply, the natural voltage and current between electrode E and electrode P, electrode P and electrode C, and electrode E and electrode C can be directly measured, the resistance between grounding electrodes EP, PC, EC can be calculated, because the electrodes are connected in series, the resistance is used as (R)_EP+R_EC-R_PC) The grounding resistance can be calculated by the following steps of/2.

The working principle of the invention is as follows:

firstly, connecting the measuring line 1 with a grounding terminal to be measured, wherein the grounding terminal to be measured is an E electrode.

And secondly, wedging the P electrode at a position 5-10 meters away from the E electrode and connecting the P electrode with the measuring line 2.

Thirdly, wedging the C electrode at the position 5-10 m away from the local P electrode along the direction of the two EP electrodes and connecting the C electrode with the measuring line 3.

And fourthly, opening the switch S4, and displaying the grounding resistance value at the measuring line 1 on the display screen of the OLED1 at the moment.

And fifthly, opening the switch S3, measuring the grounding resistance value again after moving the slide rheostat RP1 to an arbitrary value, and finishing the measurement of the grounding resistance value if the sound of opening and closing the relay is not heard.