Construction site distribution current wide-range measurement circuit and measurement method thereof

Abstract

The invention discloses a construction site distribution current wide-range measurement circuit and a measurement method thereof. The circuit comprises a current-to-voltage circuit (1), a voltage amplification circuit (2) and a current range control module (3). A first resistance switching module (5) is arranged in the current-to-voltage circuit (1), and the first resistance switching module (5) adjusts multiple conversion between an input current and an output voltage by switching resistance values; the voltage amplification circuit (2) is provided with a second resistance switching module (6), and the second resistance switching module (6) adjusts the amplification factor of the output voltage by switching resistance values; according to the invention, the current signal is amplified according to the required proportion through the multiple-adjustable current-to-voltage circuit and the voltage amplification circuit, so that the accurate measurement of the current is realized.

Description

Technical Field

[0001] The invention relates to the field of current measurement, and in particular to a large-range measurement circuit for power distribution current at a construction site and a measurement method thereof. Background Art

[0002] There are a wide variety of electrical equipment at construction sites, which not only have a wide operating power range, covering watt-level LED lighting equipment, hundred-watt-level fans, kilowatt-level indoor air conditioners, electric welders, tens of kilowatt-level elevators, tower cranes and hundred-kilowatt-level pile drivers, but also have the characteristics of temporary and frequent start and stop. Due to the above characteristics, the equipment at construction sites has an extremely large range of distribution current variations, and due to the existence of many nonlinear loads, the current distortion is serious; therefore, how to achieve a large-scale and high-precision measurement of the distribution current at construction sites is a key issue that needs to be solved to ensure the protection of distribution current at construction sites.

[0003] At present, there are two main ways to implement current detection. One is to connect the shunt resistor in series in the current loop, and the voltage across the shunt resistor carries the current information. The other is to use the current transformer CT based on the Hall principle to attenuate the current in the power line to be measured by N times and then output it from the secondary coil, and convert the current signal into a voltage signal through the resistor connected to the two ends of the secondary coil. If the resistance value of the former is too large, although the accuracy of small current can be guaranteed, the resistance heats up seriously when the current is large, which may cause safety accidents. In addition, high temperature will cause excessive temperature drift of the active and passive components of the entire measurement system, as well as the temperature drift of the shunt resistor itself, reducing the measurement accuracy. In order to meet the demand for measuring large currents, the number of turns of the secondary winding of the CT must be very large to reduce the secondary output current, suppress the temperature rise of the CT core, and avoid the demagnetization of the CT core, which will lead to a reduction in the linear range of the CT. The large number of turns of the secondary winding of the CT is conducive to measurement in large current situations, but when the distribution current at the construction site is small, in order to improve the measurement accuracy, the matching resistance of the CT output coil must be very large, so that high voltage will appear when measuring large currents, which is insufficient. Summary of the invention

[0004] The purpose of the present invention is to provide a large-range measurement circuit and a measurement method for distribution current at a construction site. The present invention uses a current-to-voltage circuit with adjustable multiples and a voltage amplifier circuit to amplify the current signal in the required proportion, thereby achieving accurate measurement of the current.

[0005] The technical solution provided by the present invention is as follows: a large-range measurement circuit for power distribution current at a construction site, comprising a current-to-voltage circuit, a voltage amplification circuit and a current range control module; a first resistance switching module is provided in the current-to-voltage circuit, and the first resistance switching module adjusts the multiple conversion between input current and output voltage by switching resistance; the voltage amplification circuit is provided with a second resistance switching module, and the second resistance switching module adjusts the amplification multiple of the output voltage by switching resistance; the input end of the current-to-voltage circuit is externally connected to the power distribution current at the construction site, and the output end of the current-to-voltage circuit is connected to the input end of the voltage amplification circuit; the input end of the current range control module is connected to the output end of the voltage amplification circuit; the output end of the current range control module is connected to the first resistance switching module and the second resistance switching module.

[0006] In the above-mentioned construction site power distribution current large-range measurement circuit, the voltage amplification circuit includes an operational amplifier OP1, a resistor R4, a resistor R5, a resistor R6 and a resistor R7, and the second resistor switching module includes a resistor R A1 , resistor R A2 , resistor R A3 , resistor R F1 , resistor R F2 , resistor R F3 、NMOS tube Q A1 、NMOS tube Q A2 、NMOS tube Q A3 、NMOS tube Q F1 、NMOS tube Q F2 And NMOS tube Q F3 The in-phase input terminal of the operational amplifier OP1 is connected to the voltage output terminal of the current-to-voltage circuit via the resistor R4, and the inverting input terminal of the operational amplifier OP1 is grounded via the resistor R5; one end of the resistor R6 is connected to the in-phase input terminal of the operational amplifier OP1, and the other end of the resistor R6 is connected in series with the resistors R A1 , resistor R A2 and resistor R A3 , resistor R A3 Connect the reference voltage; the resistor R A1 , resistor R A2 and resistor R A3 NMOS tube Q is connected in parallel A1 、NMOS tube Q A2 、NMOS tube Q A3 The output end of the operational amplifier OP1 is connected in series with a resistor R F3 , resistor R F2 , resistor R F1 and a resistor R7, the resistor R7 is connected to the inverting input terminal of the operational amplifier OP1, the resistor R F1 , resistor RF2 and resistor R F3 NMOS tube Q is connected in parallel F1 、NMOS tube Q F2 And NMOS tube Q F3 The current range control module includes an MCU, which has a PA1 output terminal, a PA2 output terminal and a PA3 output terminal, and the PA1 output terminal is connected to the NMOS tube Q A1 And NMOS tube Q F1 The gate of PA2 is connected to the NMOS tube Q A2 And NMOS tube Q F2 , the output of PA3 is connected to NMOS tube Q A3 And NMOS tube Q F3 ; The output end of the operational amplifier OP1 is connected to the input end of the current range control module.

[0007] In the above-mentioned large-range measurement circuit of power distribution current at construction sites, the resistance values ​​of the resistors R4, R5, R6 and R7 are equal; A1 and resistor R F1 The resistance value is equal, the resistor R A2 and resistor R F2 The resistance value is equal, the resistor R A3 and resistor R F3 The resistance value is equal; the resistor R A1 The resistance is a times the resistance of resistor R4. A2 The resistance is R A1 b times the resistance value, resistance R A3 The resistance is R A2 c times the resistance value, where a, b and c are all integers greater than zero.

[0008] In the aforementioned construction site power distribution current large range measurement circuit, the current-to-voltage circuit includes a current transformer CT, and the first resistance switching module includes a resistor R1, a resistor R2, a resistor R3, a relay KA1, a relay KA2 and a relay KA3; one end of the current transformer CT is connected to one end of the resistor R1, one end of the resistor R2, one end of the resistor R3 and the voltage amplification circuit; the other end of the resistor R1 is connected to one end of the relay KA1, the other end of the resistor R2 is connected to one end of the relay KA2, and the other end of the resistor R3 is connected to one end of the relay KA3; the other end of the relay KA1, the other end of the relay KA2 and the other end of the relay KA3 are connected to the other end of the current transformer CT; the control ends of the relay KA1, the relay KA2 and the relay KA3 are connected to the current range control module.

[0009] In the above-mentioned construction site power distribution current large range measurement circuit, the current range control module includes MCU, PNP transistor T1, PNP transistor T2, PNP transistor T3, resistor R T1 , resistor R T2 and resistor R T3 The MCU has a PB1 output terminal, a PB2 output terminal and a PB3 output terminal; the PB1 output terminal is connected to the resistor R T1 Connect the base of PNP transistor T1, and the output of PB2 is connected through resistor R T2 Connect the base of PNP transistor T2, and the output of PB3 is connected to the resistor R T3 The base of the PNP transistor T3 is connected, the collector of the PNP transistor T1 is connected to the control end of the relay KA1, the collector of the PNP transistor T2 is connected to the control end of the relay KA2, and the collector of the PNP transistor T3 is connected to the control end of the relay KA3; the emitters of the PNP transistor T1, the PNP transistor T2 and the PNP transistor T3 are all connected to the power supply voltage.

[0010] The aforementioned large-range measurement circuit for power distribution current at a construction site also includes a filter circuit, the input end of the filter circuit is connected to the output end of the voltage amplifier circuit, and the output end of the filter circuit is connected to the input end of the current range control module.

[0011] The measurement method of the above-mentioned construction site distribution current large-range measurement circuit is carried out according to the following steps:

[0012] Step S1: the current range control module controls the first resistance switching module and the second resistance switching module to adjust to an initialization resistance value;

[0013] Step S2: The distribution current of the construction site is converted into a voltage signal by the current-to-voltage circuit, and the voltage signal is amplified by the voltage amplifier circuit and then received and detected by the current range control module;

[0014] Step S3: the current range control module calculates the amplification factor according to the received voltage signal and controls the first resistance switching module and the second resistance switching module to switch to matching resistance values, so as to amplify the current signal by a corresponding factor.

[0015] Compared with the prior art, the current-to-voltage circuit of the present invention receives the signal of the current range control module to switch into the corresponding resistor to convert the input current i ac Converted into a voltage signal v of corresponding magnitude ac The voltage amplifier circuit receives the signal of the current range control module to cut into the corresponding resistor to convert the voltage signal v ac Amplified to a voltage signal v of corresponding magnitude o ; The current range control module obtains the voltage signal v oAnd match the corresponding control signal to switch the cut-in resistor of the current-to-voltage circuit and the voltage amplifier circuit; the present invention achieves i by adjusting the amplification factor of the current-to-voltage circuit and the voltage amplifier circuit ac Accurate proportional conversion is achieved to achieve reliable measurement of currents of various sizes. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a circuit diagram of the present invention;

[0017] Figure 2 It is a schematic diagram of the working process of the MCU of the present invention.

[0018] The markings in the attached drawings are: 1. current-to-voltage circuit; 2. voltage amplification circuit; 3. current range control module; 4. filtering circuit; 5. first resistance switching module; 6. second resistance switching module. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with the embodiments and drawings, but they are not intended to limit the present invention.

[0020] Embodiment: A large-range measurement circuit for power distribution current at a construction site, as shown in the attached Figure 1 As shown, it includes a current-to-voltage circuit 1, a voltage amplifier circuit 2 and a current range control module 3; the current-to-voltage circuit 1 is provided with a first resistance switching module 5, and the first resistance switching module 5 adjusts the multiple conversion between the input current and the output voltage by switching the resistance value; the voltage amplifier circuit 2 is provided with a second resistance switching module 6, and the second resistance switching module 6 adjusts the amplification multiple of the output voltage by switching the resistance value; the input end of the current-to-voltage circuit 1 is externally connected to the power distribution current of the construction site, and the output end of the current-to-voltage circuit 1 is connected to the input end of the voltage amplifier circuit 2; the input end of the current range control module 3 is connected to the output end of the voltage amplifier circuit 2; the output end of the current range control module 3 is connected to the first resistance switching module 5 and the second resistance switching module 6.

[0021] The voltage amplifying circuit 2 includes an operational amplifier OP1, a resistor R4, a resistor R5, a resistor R6 and a resistor R7. The second resistor switching module 6 includes a resistor R A1 , resistor R A2 , resistor R A3 , resistor R F1 , resistor R F2 , resistor R F3 、NMOS tube Q A1 、NMOS tube Q A2 、NMOS tube Q A3 、NMOS tube Q F1 、NMOS tube QF2 And NMOS tube Q F3 The in-phase input terminal of the operational amplifier OP1 is connected to the voltage output terminal of the current-to-voltage circuit via the resistor R4, and the inverting input terminal of the operational amplifier OP1 is grounded via the resistor R5; one end of the resistor R6 is connected to the in-phase input terminal of the operational amplifier OP1, and the other end of the resistor R6 is connected in series with the resistors R A1 , resistor R A2 and resistor R A3 , resistor R A3 Connect 1.024V reference voltage V ref The resistor R A1 , resistor R A2 and resistor R A3 NMOS tube Q is connected in parallel A1 、NMOS tube Q A2 、NMOS tube Q A3 The output end of the operational amplifier OP1 is connected in series with a resistor R F3 , resistor R F2 , resistor R F1 and a resistor R7, the resistor R7 is connected to the inverting input terminal of the operational amplifier OP1, the resistor R F1 , resistor R F2 and resistor R F3 NMOS tube Q is connected in parallel F1 、NMOS tube Q F2 And NMOS tube Q F3 The current range control module includes an MCU, whose reference voltage is 2.048V, and the MCU has a PA1 output terminal, a PA2 output terminal and a PA3 output terminal, and the PA1 output terminal is connected to the NMOS tube Q A1 And NMOS tube Q F1 The gate of PA2 is connected to the NMOS tube Q A2 And NMOS tube Q F2 , the output of PA3 is connected to NMOS tube Q A3 And NMOS tube Q F3 The output end of the operational amplifier OP1 is connected to the input end of the current range control module; the resistance values ​​of the resistors R4, R5, R6 and R7 are equal; the resistor R A1 and resistor R F1 The resistance value is equal, the resistor R A2 and resistor R F2 The resistance value is equal, the resistor R A3 and resistor R F3 The resistance value is equal; the resistor R A1 The resistance is 9 times the resistance of resistor R4. A2 The resistance is R A190 times the resistance value, resistor R A3 The resistance is R A2 900 times the resistance, NMOS tube Q A1 、NMOS tube Q A2 、NMOS tube Q A3 、NMOS tube Q F1 、NMOS tube Q F2 And NMOS tube Q F3 The saturated on-resistance is 20 milliohms;

[0022] When PA1=PA2=PA3=1 (i.e., PA1 output terminal, PA2 output terminal, and PA3 output terminal output high level), NMOS tube Q A1 、NMOS tube Q A2 、NMOS tube Q A3 、NMOS tube Q F1 、NMOS tube Q F2 And NMOS tube Q F3 Saturation conduction, connected between the inverting input terminal of the operational amplifier OP1 and the output terminal v o The resistor R7 is connected between the non-inverting input terminal of the operational amplifier OP1 and V ref The resistor R6 is between them. According to the knowledge of electrical engineering, we know that the voltage signal v o With v ac The relationship within operational amplifier OP1 is:

[0023] v o =V ref +v ac R6 / R4=V ref +v ac ;

[0024] Similarly, when PA1=0 (i.e. output low level), PA2=PA3=1, NMOS tube Q A2 、NMOS tube Q A3 、NMOS tube Q F2 And NMOS tube Q F3 Saturation conduction, NMOS tube Q A1 And NMOS tube Q F1 Therefore, the inverting input terminal of the operational amplifier OP1 and the output terminal v of the operational amplifier OP1 are connected. o The resistance between the resistors is 10 times that of the resistor R4, and is connected between the non-inverting input terminal of the operational amplifier OP1 and V ref The resistance between them is 10 times that of resistor R4. o With v ac Satisfies the following formula:

[0025] v o =Vref +v ac 10R4 / R4=V ref +10v ac ;

[0026] By analogy, when PA3=1, PA1=PA2=0, v o With v ac Satisfies the following formula:

[0027] v o =V ref +v ac 100R4 / R4=V ref +100v ac ;

[0028] When PA1=PA2=PA3=0, v o With v ac Satisfies the following formula:

[0029] v o =V ref +v ac 1000R4 / R4=V ref +1000v ac ;

[0030] Realize the adjustment of magnification.

[0031] The current-to-voltage circuit 1 includes a current transformer CT, and the first resistance switching module 5 includes a resistor R1, a resistor R2, a resistor R3, a relay KA1, a relay KA2 and a relay KA3; one end of the current transformer CT is connected to one end of the resistor R1, one end of the resistor R2, one end of the resistor R3 and a voltage amplifier circuit; the other end of the resistor R1 is connected to one end of the relay KA1, the other end of the resistor R2 is connected to one end of the relay KA2, and the other end of the resistor R3 is connected to one end of the relay KA3; the other end of the relay KA1, the other end of the relay KA2 and the other end of the relay KA3 are connected to the other end of the current transformer CT; the control ends of the relay KA1, the relay KA2 and the relay KA3 are connected to the current range control module; the transformation ratio N of the current transformer CT is 5000, the resistance value of the resistor R1 is 5Ω, the resistance value of the resistor R2 is 50Ω, and the resistance value of the resistor R3 is 1kΩ; the current range control module includes an MCU, a PNP transistor T1, a PNP transistor T2, a PNP transistor T3, a resistor R T1 , resistor R T2 and resistor R T3 The MCU has a PB1 output terminal, a PB2 output terminal and a PB3 output terminal; the PB1 output terminal is connected to the resistor R T1 Connect the base of PNP transistor T1, and the output of PB2 is connected through resistor RT2 Connect the base of PNP transistor T2, and the output of PB3 is connected to the resistor R T3 The base of the PNP transistor T3 is connected, the collector of the PNP transistor T1 is connected to the control end of the relay KA1, the collector of the PNP transistor T2 is connected to the control end of the relay KA2, and the collector of the PNP transistor T3 is connected to the control end of the relay KA3; the emitters of the PNP transistors T1, T2 and T3 are all connected to a 5V power supply voltage, and the output ends output signals of different levels to control the conduction of the transistors, thereby controlling the relay to close or open; when the output ends PB1, PB2 and PB3 output signals of different levels, v ac and i ac The following relations are satisfied:

[0032]

[0033] Realize the adjustment of magnification.

[0034] The filter circuit 4 includes a filter circuit, the input end of the filter circuit is connected to the output end of the voltage amplifier circuit, and the output end of the filter circuit is connected to the input end of the current range control module. The filter circuit is composed of an active filter circuit or a passive filter circuit, which is a technical means well known and mastered by those skilled in the art. The circuit composition is not repeated here. The output end signal v of the voltage amplifier circuit is o Perform high frequency and anti-aliasing filtering to filter out v o The interference gets the sampled voltage v samp , and output it to the AD sampling port of MCU;

[0035] As attached Figure 2 As shown, the MCU needs to initialize the port before working, and the initial values ​​are PB1=PB2=1, PB3=0, PA1=PA2=PA3=1, that is, relay KA3 is turned on, relay KA1 and relay KA2 are turned off; NMOS tube Q A1 、NMOS tube Q A2 、NMOS tube Q A3 、NMOS tube Q F1 、NMOS tube Q F2 And NMOS tube Q F3 The resistor R3 is connected to both ends of the output coil of the current transformer CT. The resistors R6 and R7 are the cut-in resistors of the voltage amplifier circuit. At this time, the output voltage signal v of the voltage amplifier circuit is o with i ac Satisfy: v o =V ref +i ac / 5;

[0036] MCU gets v sampAnd calculate the current i ac The effective value of I RMS , the relationship is as follows:

[0037] I RMS =K amp (V-1.024);

[0038] Where K amp The initialization value of is 0.2 (coefficient value);

[0039] MCU based on I RMS The size of the lookup table determines the amplification factor of the current-to-voltage circuit and the voltage amplifier circuit, and then controls the level signal at the output end.

[0040] In summary, the current range control module of the present invention obtains v samp Calculate i ac The effective value of I RMS The amplification factor of the current-to-voltage circuit and the voltage amplifier circuit is obtained by looking up the table, and then the relay KA1, relay KA2, relay KA3 and NMOS tube Q are controlled. A1 、NMOS tube Q A2 、NMOS tube Q A3 、NMOS tube Q F1 、NMOS tube Q F2 And NMOS tube Q F3 The on-off state; when the current i ac When the current is very small, a large matching resistor and amplification factor of the voltage amplifier circuit can be selected to achieve high-resolution measurement of tiny currents. ac When the current is too large, a small matching resistor and amplification factor of the voltage amplifier circuit should be selected to achieve high-precision detection of the current and prevent excessive matching resistors and amplification factors from causing V samp Exceeded sampling range.

Claims

1. A large-range measurement circuit for power distribution current at a construction site, characterized in that: The invention comprises a current-to-voltage circuit (1), a voltage amplifying circuit (2) and a current range control module (3); the current-to-voltage circuit (1) is provided with a first resistance switching module (5), the first resistance switching module (5) adjusts the multiple conversion between input current and output voltage by switching resistance value; the voltage amplifying circuit (2) is provided with a second resistance switching module (6), the second resistance switching module (6) adjusts the amplification multiple of the output voltage by switching resistance value; the input end of the current-to-voltage circuit (1) is externally connected to the distribution current of the construction site, the output end of the current-to-voltage circuit (1) is connected to the input end of the voltage amplifying circuit (2); the input end of the current range control module (3) is connected to the output end of the voltage amplifying circuit (2); the output end of the current range control module (3) is connected to the first resistance switching module (5) and the second resistance switching module (6).

2. The large-range measurement circuit for power distribution current at a construction site according to claim 1, characterized in that: The voltage amplification circuit (2) comprises an operational amplifier OP1, a resistor R4, a resistor R5, a resistor R6 and a resistor R7, and the second resistor switching module (6) comprises a resistor R A1 , resistor R A2 , resistor R A3 , resistor R F1 , resistor R F2 , resistor R F3 、NMOS tube Q A1 、NMOS tube Q A2 、NMOS tube Q A3 、NMOS tube Q F1 、NMOS tube Q F2 And NMOS tube Q F3 The in-phase input terminal of the operational amplifier OP1 is connected to the voltage output terminal of the current-to-voltage circuit (1) via the resistor R4, and the inverting input terminal of the operational amplifier OP1 is grounded via the resistor R5; one end of the resistor R6 is connected to the in-phase input terminal of the operational amplifier OP1, and the other end of the resistor R6 is connected in series with the resistors R A1 , resistor R A2 and resistor R A3 , resistor R A3 Connect the reference voltage; the resistor R A1 , resistor R A2 and resistor R A3 NMOS tube Q is connected in parallel A1 、NMOS tube Q A2 、NMOS tube Q A3 The output end of the operational amplifier OP1 is connected in series with a resistor R F3 , resistor R F2 , resistor R F1 and a resistor R7, the resistor R7 is connected to the inverting input terminal of the operational amplifier OP1, the resistor R F1 , resistor R F2 and resistor R F3 NMOS tube Q is connected in parallel F1 、NMOS tube Q F2 And NMOS tube Q F3 The current range control module (3) includes an MCU, which has a PA1 output terminal, a PA2 output terminal and a PA3 output terminal, and the PA1 output terminal is connected to the NMOS tube Q A1 And NMOS tube Q F1 The gate of PA2 is connected to the NMOS tube Q A2 And NMOS tube Q F2 , the output of PA3 is connected to NMOS tube Q A3 And NMOS tube Q F3 The output end of the operational amplifier OP1 is connected to the input end of the current range control module (3).

3. The large-range measurement circuit for power distribution current at a construction site according to claim 2, characterized in that: The resistance values ​​of the resistors R4, R5, R6 and R7 are equal; A1 and resistor R F1 The resistance value is equal, the resistor R A2 and resistor R F2 The resistance value is equal, the resistor R A3 and resistor R F3 The resistance value is equal; the resistor R A1 The resistance is a times the resistance of resistor R4. A2 The resistance is R A1 b times the resistance value, resistance R A3 The resistance is R A2 c times the resistance value, where a, b and c are all integers greater than zero.

4. The large-range measurement circuit for power distribution current at a construction site according to claim 1 is characterized in that: The current-to-voltage circuit (1) comprises a current transformer CT, and the first resistance switching module (5) comprises a resistor R1, a resistor R2, a resistor R3, a relay KA1, a relay KA2 and a relay KA3; one end of the current transformer CT is connected to one end of the resistor R1, one end of the resistor R2, one end of the resistor R3 and a voltage amplification circuit (2); the other end of the resistor R1 is connected to one end of the relay KA1, the other end of the resistor R2 is connected to one end of the relay KA2, and the other end of the resistor R3 is connected to one end of the relay KA3; the other end of the relay KA1, the other end of the relay KA2 and the other end of the relay KA3 are connected to the other end of the current transformer CT; and the control ends of the relays KA1, KA2 and KA3 are connected to the current range control module (3).

5. The large-range measurement circuit for power distribution current at a construction site according to claim 4, characterized in that: The current range control module (3) comprises an MCU, a PNP transistor T1, a PNP transistor T2, a PNP transistor T3, a resistor R T1 , resistor R T2 and resistor R T3 , the MCU has a PB1 output terminal, a PB2 output terminal and a PB3 output terminal; The PB1 output terminal is connected to the resistor R T1 Connect the base of PNP transistor T1, and the output of PB2 is connected through resistor R T2 Connect the base of PNP transistor T2, and the output of PB3 is connected to the resistor R T3 The base of the PNP transistor T3 is connected, the collector of the PNP transistor T1 is connected to the control end of the relay KA1, the collector of the PNP transistor T2 is connected to the control end of the relay KA2, and the collector of the PNP transistor T3 is connected to the control end of the relay KA3; the emitters of the PNP transistor T1, the PNP transistor T2 and the PNP transistor T3 are all connected to the power supply voltage.

6. The large-range measurement circuit for power distribution current at a construction site according to claim 1, characterized in that: It also includes a filter circuit (4), wherein the input end of the filter circuit (4) is connected to the output end of the voltage amplifier circuit (2), and the output end of the filter circuit (4) is connected to the input end of the current range control module (3).

7. The method for measuring a large-range measurement circuit for power distribution current at a construction site according to any one of claims 1 to 6, characterized in that: Follow these steps: Step S1: the current range control module (3) controls the first resistance switching module (5) and the second resistance switching module (6) to adjust to an initialization resistance value; Step S2: the distribution current of the construction site is converted into a voltage signal by the current-to-voltage circuit (1), the voltage signal is amplified by the voltage amplifier circuit (2), and then received and detected by the current range control module (3); Step S3: the current range control module (3) calculates the amplification factor based on the received voltage signal and controls the first resistance switching module (5) and the second resistance switching module (6) to switch to matching resistance values, thereby achieving amplification of the current signal by a corresponding factor.

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