阅读说明：本技术 电流测量装置和方法 (Current measuring device and method ) 是由 孙衍翀 周鹏 于 2021-07-27 设计创作，主要内容包括：本申请涉及一种电流测量装置和方法。所述装置包括：多个采样电阻串联形成的测量支路、与多个采样电阻一一对应的多个开关、第一运算放大器、第二运算放大器、第一模数转换器、第二模数转换器以及处理器。通过与采样电阻一一对应的开关来选择测量支路中的哪些采样电阻接入测量电路。通过更换闭合的开关,来改变测量支路的电阻值,进而切换电流测量的量程。处理器根据待测信号切换闭合的开关,在切换闭合的开关的过程中,根据第一模数转换器的测量值,确定待测电流值。该装置能够根据待测信号自动切换测量的量程,并且在切换量程的过程中保持对电流信号的测量。(The present application relates to a current measuring device and method. The device comprises: the device comprises a measuring branch formed by connecting a plurality of sampling resistors in series, a plurality of switches in one-to-one correspondence with the plurality of sampling resistors, a first operational amplifier, a second operational amplifier, a first analog-to-digital converter, a second analog-to-digital converter and a processor. And selecting which sampling resistors in the measuring branch are connected into the measuring circuit through switches in one-to-one correspondence with the sampling resistors. The resistance value of the measuring branch is changed by replacing the closed switch, and the measuring range of the current measurement is further switched. The processor switches the closed switch according to the signal to be measured, and determines the current value to be measured according to the measured value of the first analog-to-digital converter in the process of switching the closed switch. The device can automatically switch the measuring range according to the signal to be measured, and keeps the measurement of the current signal in the process of switching the measuring range.)

1. A current measuring device, characterized in that the device comprises:

the range switching circuit comprises a plurality of sampling resistors (10) and a plurality of range selection switches (20) which correspond to one another one by one; the sampling resistors (10) are connected in series, the sampling resistors (10) at two ends are respectively a first resistor (11) and a second resistor (12), and one end, close to the first resistor (11) or far away from the second resistor (12), of each sampling resistor (10) is a first end; a first end of each range selection switch (20) is connected with a second end of the corresponding sampling resistor (10), and second ends of the plurality of range selection switches (20) are connected together; at least one of the plurality of range selection switches (20) is closed, and the first end of the first resistor (11) and the second ends of the plurality of range selection switches (20) are the input end and the output end of the current signal to be measured in the range switching circuit;

a maximum measuring range measuring unit comprising a first operational amplifier (30) and a first analog-to-digital converter (40) connected; the first operational amplifier (30) is respectively connected with the first end and the second end of the first resistor (11) and is used for measuring the voltage formed by the current signal to be measured on the first resistor (11), generating a voltage measurement signal and scaling the voltage measurement signal; the first analog-to-digital converter (40) is used for measuring the voltage measurement signal after the first operational amplifier (30) is scaled, so as to obtain a first voltage value;

the adjustable range measuring unit comprises a second operational amplifier (31) and a second analog-to-digital converter (41) which are connected; the second operational amplifier (31) is respectively connected with the first end of the first resistor (11) and the second end of the second resistor (12) and is used for measuring the voltage formed by the current signal to be measured on the plurality of sampling resistors (10), generating a voltage measurement signal and scaling the voltage measurement signal; the second analog-to-digital converter (41) is used for measuring the voltage measurement signal obtained by scaling the second operational amplifier (31) to obtain a second voltage value;

a processor (50) respectively connected to the first analog-to-digital converter (40), the control terminals of the plurality of range selection switches (20), and the second analog-to-digital converter (41), and configured to determine a target range of the adjustable range measurement unit based on the first voltage value when the range selection switch (20) corresponding to the first resistor (11) is closed, where the target range corresponds to one of the plurality of range selection switches (20), and a measurement range of the adjustable range measurement unit when the range selection switch (20) corresponding to the target range is closed is the target range; within a first set time length after the target measuring range is determined, closing a measuring range selection switch (20) corresponding to the target measuring range; disconnecting all range selection switches (20) except the range selection switch (20) corresponding to the target range between the first set time length and the second set time length after the target range is determined; and determining a first current value corresponding to the current signal to be measured and outputting the first current value based on the first voltage value in a second set time length after the target measuring range is determined.

2. The apparatus of claim 1 wherein the processor (50) is configured to determine a proportion of the first current value in each measurement range of the adjustable range measurement unit; screening out the proportion which is smaller than the upper limit of the proportion and larger than the lower limit of the proportion; determining the measuring range corresponding to the maximum proportion in the screened proportions as the target range; the upper proportional limit is a judgment reference for determining whether a second current value exceeds the upper measuring range limit of the adjustable measuring range measuring unit, the lower proportional limit is a judgment reference for determining whether the second current value is lower than the lower measuring range limit of the adjustable measuring range measuring unit, and the second current value is a current value corresponding to the current signal to be measured and determined based on the second voltage value.

3. The apparatus of claim 1 wherein the processor (50) is configured to determine a target range of the adjustable range measurement unit based on the first voltage value when the first current value is within a second large measurement range of the adjustable range measurement unit.

4. The apparatus of claim 1 wherein the processor (50) is configured to output the first current value determined at a first time when the first current value determined at the first time is outside the second wide-measurement range of the adjustable-range measurement unit; judging whether the first current value determined at the second moment is out of the second large measuring range of the adjustable measuring range measuring unit or not; wherein the second time is after the first time.

5. The device according to claim 3 or 4, wherein the processor (50) is configured to determine whether the first current value is greater than an upper value of the second large measurement range of the adjustable range measurement unit or less than a lower value of the second large measurement range of the adjustable range measurement unit; if the first current value is larger than the upper limit value of the second large measuring range of the adjustable measuring range measuring unit or smaller than the lower limit value of the second large measuring range of the adjustable measuring range measuring unit, determining that the first current value is out of the second large measuring range of the adjustable measuring range measuring unit; and if the first current value is smaller than the upper limit value of the second large measuring range of the adjustable measuring range measuring unit and larger than the lower limit value of the second large measuring range of the adjustable measuring range measuring unit, determining that the first current value is in the second large measuring range of the adjustable measuring range measuring unit.

6. The device according to any one of claims 1 to 4, wherein the processor (50) is configured to determine a second current value corresponding to the current signal to be measured based on the second voltage value for a second set time period after the target measuring range is determined; when the second current value determined at the first moment is within the target range and the target range is the minimum measuring range of all measuring ranges of the second current value determined at the first moment, outputting the second current value determined at the first moment; judging whether the second current value determined at the second moment is within the target range and whether the target range is the minimum measurement range in all measurement ranges of the second current value determined at the second moment; wherein the second time is after the first time.

7. The device of claim 6, wherein the processor (50) is configured to close the range selection switch (20) associated with the first resistor (11) when the second current value is outside the target range, or the target range is not a minimum measurement range of all measurement ranges of the second current value.

8. The apparatus of claim 6, wherein the processor (50) is configured to determine a proportion of the second voltage value in a measurement range of the second analog-to-digital converter (41); when the proportion of the second voltage value in the measuring range of the second analog-to-digital converter (41) is between a proportion upper limit and a proportion lower limit, determining that the second current value is in the measuring range of the adjustable range measuring unit; and when the proportion of the second voltage value in the current measuring range of the second analog-to-digital converter (41) is larger than the upper proportion limit or smaller than the lower proportion limit, determining that the second current value is out of the measuring range of the adjustable range measuring unit.

9. The apparatus of claim 8, wherein the processor (50) is configured to, when the second voltage value increases gradually, take a first upper scale limit as the upper scale limit and a first lower scale limit as the lower scale limit; and when the second voltage value is gradually reduced, taking a second proportion upper limit as the proportion upper limit, taking a second proportion lower limit as the proportion lower limit, wherein the second proportion upper limit is smaller than the first proportion upper limit, and the second proportion lower limit is smaller than the first proportion lower limit.

10. A method of measuring current, the method comprising:

the current signal to be measured passes through the pass switching circuit; the range switching circuit comprises a plurality of sampling resistors and a plurality of range selection switches which are in one-to-one correspondence; the sampling resistors are connected in series, the sampling resistors at two ends are respectively a first resistor and a second resistor, and one end of each sampling resistor, which is close to the first resistor or far away from the second resistor, is a first end; the first end of each range selection switch is connected with the second end of the corresponding sampling resistor, and the second ends of the plurality of range selection switches are connected together; the first end of the first resistor and the second ends of the plurality of range selection switches are input ends and output ends of current signals to be measured in the range switching circuit;

closing at least one of the plurality of span select switches;

measuring the voltage formed by the current signal to be measured on the first resistor through a first operational amplifier, generating a voltage measurement signal and scaling;

measuring the voltage measurement signal obtained by scaling the first operational amplifier through a first analog-to-digital converter to obtain a first voltage value; the first operational amplifier and the first analog-to-digital converter are connected to form a maximum measuring range measuring unit;

measuring the voltage formed by the current signal to be measured on the plurality of sampling resistors through a second operational amplifier, generating a voltage measurement signal and scaling;

measuring the amplified voltage signal of the second operational amplifier after being zoomed through a second analog-to-digital converter to obtain a second voltage value; the second operational amplifier and the second analog-to-digital converter are connected to form an adjustable range measuring unit;

when the range selection switch corresponding to the first resistor is closed, determining a target range of the adjustable range measurement unit based on the first voltage value, wherein the target range corresponds to one of the range selection switches, and the measurement range of the adjustable range measurement unit when the range selection switch corresponding to the target range is closed is the target range;

within a first set time length after the target range is determined, closing a range selection switch corresponding to the target range;

disconnecting all the range selection switches except the range selection switch corresponding to the target range between the first set time length and the second set time length after the target range is determined;

and determining a first current value corresponding to the current signal to be measured and outputting the first current value based on the first voltage value in a second set time length after the target measuring range is determined.

Technical Field

The present disclosure relates to circuit measurement technologies, and in particular, to a current measurement device and method.

Background

With the development of electronic circuit technology, the requirements for the continuity and accuracy of the measured current are higher and higher. For different current signals, different measuring ranges are required to be used for measurement, so that the measurement accuracy is improved.

In the conventional technology, the measuring range of the current measuring device is adjusted manually by controlling the action of a selection switch according to a current signal to be measured.

However, the conventional scheme for adjusting the range cannot automatically switch the range of the current measuring device. In addition, because the action of the selection switch requires a certain time, the scheme in the conventional technology can cause the measurement channel of the current to be broken in the action process of the selection switch, thereby causing interruption and missing measurement of the current measurement and causing inaccurate measurement.

Disclosure of Invention

In view of the above, it is desirable to provide a current measuring device and method capable of automatically switching a range according to a signal to be measured and maintaining accurate measurement of a current during switching of the range.

A current measurement device, the device comprising: the range switching circuit comprises a plurality of sampling resistors and a plurality of range selection switches which correspond to one another one by one; the sampling resistors are connected in series, the sampling resistors at two ends are respectively a first resistor and a second resistor, and one end of each sampling resistor, which is close to the first resistor or far away from the second resistor, is a first end; the first end of each range selection switch is connected with the second end of the corresponding sampling resistor, and the second ends of the plurality of range selection switches are connected together; at least one of the plurality of range selection switches is closed, and the first end of the first resistor and the second ends of the plurality of range selection switches are the input end and the output end of the current signal to be measured in the range switching circuit; the maximum measuring range measuring unit comprises a first operational amplifier and a first analog-to-digital converter which are connected; the first operational amplifier is respectively connected with the first end and the second end of the first resistor and is used for measuring the voltage formed by the current signal to be measured on the first resistor, generating a voltage measurement signal and scaling the voltage measurement signal; the first analog-to-digital converter is used for measuring the voltage measurement signal obtained by scaling the first operational amplifier to obtain a first voltage value; the adjustable measuring range measuring unit comprises a second operational amplifier and a second analog-to-digital converter which are connected; the second operational amplifier is respectively connected with the first end of the first resistor and the second end of the second resistor and is used for measuring the voltage formed by the current signal to be measured on the plurality of sampling resistors, generating a voltage measurement signal and scaling the voltage measurement signal; the second analog-to-digital converter is used for measuring the voltage measurement signal obtained by scaling the second operational amplifier to obtain a second voltage value; a processor, connected to the first analog-to-digital converter, the control terminals of the multiple range selection switches, and the second analog-to-digital converter, respectively, and configured to determine a target range of the adjustable range measurement unit based on the first voltage value when the range selection switch corresponding to the first resistor is turned off, where the target range corresponds to one of the multiple range selection switches, and a measurement range of the adjustable range measurement unit when the range selection switch corresponding to the target range is turned off is the target range; within a first set time length after the target range is determined, closing a range selection switch corresponding to the target range; disconnecting all the range selection switches except the range selection switch corresponding to the target range between the first set time length and the second set time length after the target range is determined; and determining a first current value corresponding to the current signal to be measured and outputting the first current value based on the first voltage value in a second set time length after the target measuring range is determined.

In one embodiment, the processor is configured to determine a proportion of the first current value in each measurement range of the adjustable range measurement unit; screening out the proportion which is smaller than the upper limit of the proportion and larger than the lower limit of the proportion; determining the measuring range corresponding to the maximum proportion in the screened proportions as the target range; the upper proportional limit is a judgment reference for determining whether a second current value exceeds the upper measuring range limit of the adjustable measuring range measuring unit, the lower proportional limit is a judgment reference for determining whether the second current value is lower than the lower measuring range limit of the adjustable measuring range measuring unit, and the second current value is a current value corresponding to the current signal to be measured and determined based on the second voltage value.

In one embodiment, the processor is configured to determine a target range of the adjustable range measurement unit based on the first voltage value when the first current value is within a second large measurement range of the adjustable range measurement unit.

In one embodiment, the processor is configured to output the first current value determined at the first time when the first current value determined at the first time is outside the second large measurement range of the adjustable range measurement unit; judging whether the first current value determined at the second moment is out of the second large measuring range of the adjustable measuring range measuring unit or not; wherein the second time is after the first time.

In one embodiment, the processor is configured to determine whether the first current value is greater than an upper value of the second large measurement range of the adjustable range measurement unit or less than a lower value of the second large measurement range of the adjustable range measurement unit; if the first current value is larger than the upper limit value of the second large measuring range of the adjustable measuring range measuring unit or smaller than the lower limit value of the second large measuring range of the adjustable measuring range measuring unit, determining that the first current value is out of the second large measuring range of the adjustable measuring range measuring unit; if the first current value is smaller than the upper limit value of the second large measuring range of the adjustable measuring range measuring unit and larger than the lower limit value of the second large measuring range of the adjustable measuring range measuring unit, determining that the first current value is in the second large measuring range of the adjustable measuring range measuring unit

In one embodiment, the processor is used for determining a second current value corresponding to the current signal to be measured based on the second voltage value outside a second set time length after the target measuring range is determined; when the second current value determined at the first moment is within the target range and the target range is the minimum measurement range in all measurement ranges of the second current value at the first moment, outputting the second current value determined at the first moment; judging whether the second current value determined at the second moment is out of the target range or not, or whether the target range is the minimum measurement range in all measurement ranges of the second current value at the second moment; wherein the second time is after the first time.

In one embodiment, the processor is configured to close the range selection switch corresponding to the first resistor when the second current value is outside the target range, or the target range is not the minimum measurement range of all measurement ranges of the second current value.

In one embodiment, the processor is configured to determine a proportion of the second voltage value in a measurement range of the second analog-to-digital converter; when the proportion of the second voltage value in the measurement range of the second analog-to-digital converter is between the upper proportion limit and the lower proportion limit, determining that the second current value is in the measurement range of the adjustable range measurement unit; and when the proportion of the second voltage value in the measurement range of the second analog-to-digital converter is greater than the upper proportion limit or less than the lower proportion limit, determining that the second current value is out of the measurement range of the adjustable range measurement unit.

In one embodiment, the processor is configured to, when the second voltage value gradually increases, take a first upper ratio limit as the upper ratio limit and a first lower ratio limit as the lower ratio limit; and when the second voltage value is gradually reduced, taking a second proportion upper limit as the proportion upper limit, taking a second proportion lower limit as the proportion lower limit, wherein the second proportion upper limit is smaller than the first proportion upper limit, and the second proportion lower limit is smaller than the first proportion lower limit.

A method of current measurement, the method comprising: the current signal to be measured passes through the pass switching circuit; the range switching circuit comprises a plurality of sampling resistors and a plurality of range selection switches which are in one-to-one correspondence; the sampling resistors are connected in series, the sampling resistors at two ends are respectively a first resistor and a second resistor, and one end of each sampling resistor, which is close to the first resistor or far away from the second resistor, is a first end; the first end of each range selection switch is connected with the second end of the corresponding sampling resistor, and the second ends of the plurality of range selection switches are connected together; the first end of the first resistor and the second ends of the plurality of range selection switches are input ends and output ends of current signals to be measured in the range switching circuit;

closing at least one of the plurality of span select switches;

measuring the voltage formed by the current signal to be measured on the first resistor through a first operational amplifier, generating a voltage measurement signal and scaling;

measuring the voltage measurement signal obtained by scaling the first operational amplifier through a first analog-to-digital converter to obtain a first voltage value; the first operational amplifier and the first analog-to-digital converter are connected to form a maximum measuring range measuring unit;

measuring the voltage formed by the current signal to be measured on the plurality of sampling resistors through a second operational amplifier, generating a voltage measurement signal and scaling;

measuring the amplified voltage signal of the second operational amplifier after being zoomed through a second analog-to-digital converter to obtain a second voltage value; the second operational amplifier and the second analog-to-digital converter are connected to form an adjustable range measuring unit;

when the range selection switch corresponding to the first resistor is closed, determining a target range of the adjustable range measurement unit based on the first voltage value, wherein the target range corresponds to one of the range selection switches, and the measurement range of the adjustable range measurement unit when the range selection switch corresponding to the target range is closed is the target range;

within a first set time length after the target range is determined, closing a range selection switch corresponding to the target range;

disconnecting all the range selection switches except the range selection switch corresponding to the target range between the first set time length and the second set time length after the target range is determined;

and determining a first current value corresponding to the current signal to be measured and outputting the first current value based on the first voltage value in a second set time length after the target measuring range is determined.

The current measuring device and the method form a range switching circuit by a plurality of sampling resistors and a plurality of range selection switches which are in one-to-one correspondence, the sampling resistors are connected in series, the sampling resistors at two ends are respectively a first resistor and a second resistor, one end of each sampling resistor, which is close to the first resistor or far away from the second resistor, is a first end, the first end of each range selection switch is connected with the second end of the corresponding sampling resistor, the second ends of the range selection switches are connected together, at least one of the range selection switches is closed, and the first end of the first resistor and the second ends of the range selection switches are input ends and output ends of current signals to be measured. In this way, the current signal to be measured only passes through the sampling resistor between the first resistor and the sampling resistor corresponding to the closed range selection switch, and the sampling resistor between the sampling resistor corresponding to the closed range selection switch and the second resistor is short-circuited. The quantity of sampling resistors through which current signals to be measured pass can be changed by selecting different range selection switches to be closed, so that the size of the resistor through which the current signals to be measured pass is changed, and the voltage formed by the current signals to be measured on the sampling resistors is controlled within the measuring range of the measuring unit under the condition that the current signals to be measured are different in size, so that the measuring unit can accurately measure the voltage.

The method comprises the steps of connecting a first operational amplifier and a first analog-to-digital converter to form a maximum measuring range measuring unit, connecting the first operational amplifier to a first end and a second end of a first resistor respectively, measuring the voltage formed by a current signal to be measured on the first resistor, generating a voltage measuring signal and scaling the voltage measuring signal, and measuring the scaled voltage measuring signal of the first operational amplifier by the first analog-to-digital converter to obtain a first voltage value. Since the maximum range measuring unit measures only the voltage formed on one resistor of the first resistor, the maximum range measuring unit can realize measurement within the maximum range.

And the second analog-to-digital converter measures the voltage measurement signal of the second operational amplifier after being scaled to obtain a second voltage value. Because the voltage formed on the sampling resistors is determined by the closed range selection switch, and the closed range selection switch can be selected according to the size of the current signal to be measured so as to control the voltage formed on the sampling resistors within the measurement range of the measurement unit, the measurement range of the adjustable range measurement unit can be adjusted to be matched with the current signal to be measured, and the accurate measurement within a small range is realized.

When the range selection switch corresponding to the first resistor is closed, the target range of the adjustable range measuring unit is determined according to the first voltage value, the range selection switch corresponding to the target range is closed within the first set duration after the target range is determined, all range selection switches except the range selection switch corresponding to the target range are opened between the first set duration and the second set duration after the target range is determined, automatic switching of the measuring range of the adjustable range measuring unit can be achieved, at least one of the range switching switches is closed in the range switching process in the measuring range switching process, and the maximum range measuring unit can perform accurate measurement. In the process of switching the measuring range, the second voltage value measured by the adjustable measuring range measuring unit is inaccurate. And in a second set time length after the target range is determined, determining and outputting a first current value corresponding to the current signal to be measured based on the first voltage value, so that the continuity and the accuracy of the current measurement can be still maintained under the condition that the measurement result of the adjustable range measurement unit is inaccurate.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments or the conventional technologies of the present application, the drawings used in the descriptions of the embodiments or the conventional technologies will be briefly introduced below, it is obvious that the drawings in the following descriptions are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic diagram of a current measuring device according to an embodiment;

FIG. 2 is a flow chart of the operation of the current measuring device in one embodiment;

FIG. 3 is a flow diagram of current output during span switching in one embodiment;

FIG. 4 is a schematic diagram of a gradual voltage change in one embodiment;

FIG. 5 is a schematic structural diagram of a current measuring device according to another embodiment;

FIG. 6 is a flow chart illustrating a current measurement method according to an embodiment.

Description of reference numerals:

10-sampling resistor, 11-first resistor, 12-second resistor, 20-switch, 21-first short-circuit switch, 30-first operational amplifier, 40-first analog-digital converter, 31-second operational amplifier, 41-second analog-digital converter and 50-processor.

Detailed Description

To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Embodiments of the present application are set forth in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

It will be understood that, as used herein, the terms "first," "second," and the like may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another.

It will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element or be connected to the other element through intervening elements. Further, "connection" in the following embodiments is understood to mean "electrical connection", "communication connection", or the like, if there is a transfer of electrical signals or data between the connected objects.

As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises/comprising," "includes" or "including," etc., specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

The current measuring method in the current measuring device usually adopts a mode of precisely detecting a resistor and an operational amplifier, the resistance value of the resistor is known, the actual current value can be measured by measuring the voltage of the current flowing through two ends of the resistor and then by using the ohm law I as U/R. The measuring method has the advantages of low cost, high precision and small volume. By adopting the method, the influence of power parameters, design cost and other factors on the detection resistor is considered, so different detection resistors need to be selected according to the magnitude of the measurement current to form different measurement channels to switch different ranges. If the current measuring range is not matched with the current signal to be measured, the measuring precision is not high; or inaccurate measurement may occur during the switching of the range. For the reasons, the current measuring device and the method can automatically switch the measuring range and still keep accurate measurement of the current in the process of switching the measuring range.

In one embodiment, as shown in fig. 1, a current measuring device is provided, which includes a plurality of sampling resistors 10 and a plurality of range selection switches 20 in a one-to-one correspondence, a first operational amplifier 30, a first analog-to-digital converter 40, a second operational amplifier 31, a second analog-to-digital converter 41, and a processor 50. The range switching circuit comprises a plurality of sampling resistors 10 and a plurality of range selection switches 20 which correspond to one another one by one; the sampling resistors 10 are connected in series, the sampling resistors 10 at two ends are respectively a first resistor 11 and a second resistor 12, and one end of each sampling resistor 10 close to the first resistor 11 or far away from the second resistor 12 is a first end; the first end of each range selection switch 20 is connected with the second end of the corresponding sampling resistor 10, and the second ends of the range selection switches 20 are connected together; at least one of the plurality of range selection switches 20 is closed, and the first end of the first resistor 11 and the second end of the plurality of range selection switches 20 are the input end and the output end of the current signal to be measured in the range switching circuit; a maximum measurement range measuring unit including a first operational amplifier 30 and a first analog-to-digital converter 40 connected; the first operational amplifier 30 is respectively connected to the first end and the second end of the first resistor 11, and is configured to measure a voltage formed by the current signal to be measured on the first resistor 11, generate a voltage measurement signal, and perform scaling; the first analog-to-digital converter 40 is configured to measure the scaled voltage measurement signal of the first operational amplifier 30 to obtain a first voltage value; the adjustable range measuring unit comprises a second operational amplifier 31 and a second analog-to-digital converter 41 which are connected; the second operational amplifier 31 is respectively connected to the first end of the first resistor 11 and the second end of the second resistor 12, and is configured to measure a voltage formed by the current signal to be measured on the plurality of sampling resistors 10, generate a voltage measurement signal, and perform scaling; the second analog-to-digital converter 41 is configured to measure the voltage measurement signal scaled by the second operational amplifier 31 to obtain a second voltage value; and the processor 50 is respectively connected with the first analog-to-digital converter 40, the control ends of the plurality of range selection switches 20 and the second analog-to-digital converter 41.

As shown in fig. 2, the processor 50 is configured to perform the following steps:

and S200, when the range selection switch corresponding to the first resistor is closed, determining the target range of the adjustable range measuring unit based on the first voltage value.

Specifically, the target range corresponds to one of the range selection switches, and the measurement range of the adjustable range measurement unit when the range selection switch corresponding to the target range is closed is the target range.

And S210, within the first set time length after the target range is determined, closing the range selection switch corresponding to the target range.

And S220, disconnecting all the range selection switches except the range selection switch corresponding to the target range between the first set time length and the second set time length after the target range is determined.

And S230, determining a first current value corresponding to the current signal to be measured based on the first voltage value within a second set time length after the target measuring range is determined, and outputting the first current value.

Illustratively, in the plurality of sampling resistors 10, the resistance values increase in order from the first resistor 11 to the second resistor 12, the resistance value of the first resistor 11 is the smallest, and the resistance value of the second resistor 12 is the largest.

Illustratively, the range selection switch 20 may be one of a switch tube, a relay switch, and a single pole switch.

Illustratively, the first operational amplifier 30 and the second operational amplifier 31 may be one of general operational amplifiers F003, F007, F030, a high speed operational amplifier F051B, a high precision operational amplifier F714, a high impedance operational amplifier CF072, and a low power operational amplifier F010.

Illustratively, the first analog-to-digital converter 40 and the second analog-to-digital converter 41 may be one of ADCs 0808, AD7678, AD9221, AD9223, and AD 9220.

Illustratively, the Processor 50 may be a Central Processing Unit (CPU), and may be one of other general purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field-Programmable Gate arrays (FPGAs) or other Programmable logic devices, discrete Gate or transistor logic devices, discrete hardware components, and the like. The general purpose processor may be a microprocessor or any conventional processor.

In this embodiment, a range switching circuit is composed of a plurality of sampling resistors and a plurality of range selection switches in one-to-one correspondence, the plurality of sampling resistors are connected in series, the sampling resistors at two ends are respectively a first resistor and a second resistor, one end of each sampling resistor, which is close to the first resistor or is far away from the second resistor, is a first end, the first end of each range selection switch is connected with the second end of the corresponding sampling resistor, the second ends of the plurality of range selection switches are connected together, at least one of the plurality of range selection switches is closed, and the first end of the first resistor and the second ends of the plurality of range selection switches are input ends and output ends of current signals to be measured. In this way, the current signal to be measured only passes through the sampling resistor between the first resistor and the sampling resistor corresponding to the closed range selection switch, and the sampling resistor between the sampling resistor corresponding to the closed range selection switch and the second resistor is short-circuited. The quantity of sampling resistors through which current signals to be measured pass can be changed by selecting different range selection switches to be closed, so that the size of the resistor through which the current signals to be measured pass is changed, and the voltage formed by the current signals to be measured on the sampling resistors is controlled within the measuring range of the measuring unit under the condition that the current signals to be measured are different in size, so that the measuring unit can accurately measure the voltage.

The method comprises the steps of connecting a first operational amplifier and a first analog-to-digital converter to form a maximum measuring range measuring unit, connecting the first operational amplifier to a first end and a second end of a first resistor respectively, measuring the voltage formed by a current signal to be measured on the first resistor, generating a voltage measuring signal and scaling the voltage measuring signal, and measuring the scaled voltage measuring signal of the first operational amplifier by the first analog-to-digital converter to obtain a first voltage value. Since the maximum range measuring unit measures only the voltage formed on one resistor of the first resistor, the maximum range measuring unit can realize measurement within the maximum range.

And the second analog-to-digital converter measures the voltage measurement signal of the second operational amplifier after being scaled to obtain a second voltage value. Because the voltage formed on the sampling resistors is determined by the closed range selection switch, and the closed range selection switch can be selected according to the size of the current signal to be measured so as to control the voltage formed on the sampling resistors within the measurement range of the measurement unit, the measurement range of the adjustable range measurement unit can be adjusted to be matched with the current signal to be measured, and the accurate measurement within a small range is realized.

When the range selection switch corresponding to the first resistor is closed, the target range of the adjustable range measuring unit is determined according to the first voltage value, the range selection switch corresponding to the target range is closed within the first set duration after the target range is determined, all range selection switches except the range selection switch corresponding to the target range are opened between the first set duration and the second set duration after the target range is determined, automatic switching of the measuring range of the adjustable range measuring unit can be achieved, at least one of the range switching switches is closed in the range switching process in the measuring range switching process, and the maximum range measuring unit can perform accurate measurement. In the process of switching the measuring range, the second voltage value measured by the adjustable measuring range measuring unit is inaccurate. And in a second set time length after the target range is determined, determining and outputting a first current value corresponding to the current signal to be measured based on the first voltage value, so that the continuity and the accuracy of the current measurement can be still maintained under the condition that the measurement result of the adjustable range measurement unit is inaccurate.

In one embodiment, as shown in FIG. 3, processor 50 is configured to perform the following steps:

and S300, closing the range selection switch corresponding to the first resistor.

Specifically, after the range selection switch corresponding to the first resistor is closed, the maximum range measurement unit can accurately measure the current signal to be measured, and determine a first current value corresponding to the current signal to be measured based on the obtained first voltage value.

S310, determining a first current value corresponding to the current signal to be measured based on the first voltage value, and judging whether the first current value is in the second large measuring range of the adjustable measuring range measuring unit. If the first current value is within the second large measuring range of the adjustable measuring range measuring unit, executing step S330; if the first current value is outside the second large measuring range of the adjustable-range measuring unit, step S320 is executed.

Specifically, the processor 50 is configured to determine whether the first current value is greater than an upper limit value of the second large measurement range of the adjustable-range measurement unit or less than a lower limit value of the second large measurement range of the adjustable-range measurement unit; if the first current value is larger than the upper limit value of the second large measuring range of the adjustable measuring range measuring unit or smaller than the lower limit value of the second large measuring range of the adjustable measuring range measuring unit, determining that the first current value is outside the second large measuring range of the adjustable measuring range measuring unit; and if the first current value is smaller than the upper limit value of the second large measuring range of the adjustable measuring range measuring unit and larger than the lower limit value of the second large measuring range of the adjustable measuring range measuring unit, determining that the first current value is in the second large measuring range of the adjustable measuring range measuring unit.

S320, outputting a first current value.

Specifically, after step S320 is performed, step S310 is performed. After the first current value determined at the first moment is output, judging whether the first current value determined at the second moment is out of the second large measuring range of the adjustable measuring range measuring unit or not; wherein the second time is after the first time.

Specifically, after the first current value is output, a new signal to be measured is received, and at this time, it may be determined again whether the first current value measured by the current maximum measurement range measuring unit is within the second large measurement range of the adjustable measurement range measuring unit, that is, after step S320 is executed, step S310 is executed again.

Specifically, if the first current value is outside the second large measurement range of the adjustable range measurement unit, it represents that the first current value can be measured only by using the maximum measurement range measurement unit or the maximum measurement range of the adjustable range measurement unit, and the first current value at this time is the most accurate value that can be measured by the current measurement device, and the first current value at this time is output without determining the target range.

And S330, determining the target range of the adjustable range measuring unit based on the first voltage value.

Specifically, the processor 50 is configured to determine a ratio of the first current value in each measurement range of the adjustable-range measurement unit; screening out the proportion smaller than the upper limit of the proportion and larger than the lower limit of the proportion; determining the measuring range corresponding to the maximum proportion in the screened proportions as a target range; the upper proportional limit is a judgment reference for determining whether the second current value exceeds the upper measuring range limit of the adjustable measuring range measuring unit, the lower proportional limit is a judgment reference for determining whether the second current value is lower than the lower measuring range limit of the adjustable measuring range measuring unit, and the second current value is a current value corresponding to the current signal to be measured and determined based on the second voltage value.

And S340, closing the range selection switch corresponding to the target range within the first set time length after the target range is determined.

And S350, disconnecting all the range selection switches except the range selection switch corresponding to the target range between the first set time length and the second set time length after the target range is determined.

And S360, determining a first current value corresponding to the current signal to be measured and outputting the first current value based on the first voltage value within a second set time length after the target measuring range is determined.

Specifically, the second set duration is longer than the first set duration, so that the range selection switches before and after switching are simultaneously closed between the first set duration and the second set duration, and the continuity of current measurement is ensured. By setting the first set time length and the second set time length, at least one range selection switch is ensured to be closed at any time, so that the current measurement is not interrupted. Meanwhile, the second set duration also ensures that the switching action of the range selection switch is completely finished.

And S370, determining a second current value corresponding to the current signal to be measured based on the second voltage value outside the second set time length after the target range of the adjustable range measuring unit is determined, and judging whether the second current value is in the target range of the adjustable range measuring unit and whether the target range is the minimum measuring range of all measuring ranges of the second current value. If the second current value is outside the target range of the adjustable range measuring unit, or the target range is not the minimum measuring range of all measuring ranges of the second current value, executing step S300; if the second current value is within the target range of the adjustable-range measuring unit and the target range is the minimum measuring range of all measuring ranges of the second current value, step S380 is executed.

Specifically, the step of judging whether the second current value is out of the target range of the adjustable range measuring unit includes the following steps: dividing the difference value between the second current value and the minimum value of the measuring range of the adjustable range measuring unit by the difference value between the maximum value and the minimum value of the measuring range of the adjustable range measuring unit to obtain the proportion of the second current value in the measuring range of the adjustable range measuring unit; when the proportion of the second current value in the measuring range of the adjustable range measuring unit is between the upper proportion limit and the lower proportion limit, determining that the second current value is in the measuring range of the adjustable range measuring unit; and when the proportion of the second current value in the measuring range of the adjustable range measuring unit is greater than the upper limit of the proportion or less than the lower limit of the proportion, determining that the second current value is outside the measuring range of the adjustable range measuring unit.

Judging whether the target measuring range is the minimum measuring range in all measuring ranges of the second current value or not, comprising the following steps: dividing the difference value between the second current value and the minimum value of the measuring range of each measurable second current value of the adjustable range measuring unit by the difference value between the corresponding maximum value and the corresponding minimum value of the measuring range respectively, and determining the proportion of the second current value in the measuring range of each measurable second current value of the adjustable range measuring unit; if the measuring range corresponding to the maximum proportion of the second current value in the proportion occupied in the measuring ranges of the second current values measurable by the adjustable range measuring unit is not the target range, determining that the target range is not the minimum measuring range in all measuring ranges of the second current value; and if the measuring range corresponding to the maximum proportion of the second current value in the proportion occupied in the measuring ranges of the second current values measurable by the adjustable range measuring unit is the target range, determining that the target range is the minimum measuring range in all the measuring ranges of the second current value.

Specifically, in the measurement range of the adjustable range measurement unit, in which the second current value can be measured, the measurement range with the largest proportion of the second current value is the minimum measurement range in which the second current value can be measured. The measured second current value is already the most accurate value that can be measured by the current measuring device.

And S380, outputting a second current value.

Specifically, after step S380 is executed, step S370 is executed. After the second current value determined at the first moment is output, whether the second current value determined at the second moment is within the target range or not and whether the target range is the minimum measurement range of all measurement ranges of the second current value measured at the second moment or not are judged.

In this embodiment, first, the range selection switch corresponding to the first resistor is closed, and at this time, the maximum range measurement unit is used to measure the current signal to be measured, so as to obtain the first voltage value. And then determining a first current value corresponding to the current signal to be measured based on the first voltage value, and judging whether the first current value is in the second large measuring range of the adjustable measuring range measuring unit. If the first current value is not in the second large measuring range of the adjustable range measuring unit, the first current value represents that the first current value can be measured only by using the maximum measuring range measuring unit or the maximum measuring range of the adjustable range measuring unit, the first current value at the moment is the most accurate value which can be measured by the current measuring device, the target range does not need to be determined, and the first current value at the moment is output. And then receiving the current signal to be measured at the next moment, and judging whether the current signal to be measured at the next moment is in the second large measuring range of the adjustable measuring range measuring unit again.

And if the first current value is within the second large measuring range of the adjustable measuring range measuring unit, determining the target measuring range of the adjustable measuring range measuring unit based on the first current value. The target range is the minimum range which can measure the first current value and does not exceed the range in all measuring ranges of the adjustable range measuring unit. Thereby achieving the most accurate measurement of the first current value.

And in a first set time length after the target range is determined, controlling a range selection switch corresponding to the target range to be closed, between the first set time length and a second set time length, disconnecting all range selection switches except the range selection switch corresponding to the target range, and in the second set time length after the target range is determined, determining and outputting a first current value corresponding to the current signal to be measured based on the first voltage value. Therefore, at any moment, at least one range selection switch is closed, so that the current measurement is not interrupted, and the continuity of the current measurement is ensured. And the switching action of the range selection switch is completely finished by setting the second time length. And in the process of switching the range selection switch, a first current value is output, so that the current measurement is ensured to be uninterrupted.

And then determining a second current value corresponding to the current signal to be measured based on the second voltage value outside a second set time length after the target measuring range is determined. And judging whether the second current value is in the target range of the adjustable range measuring unit or not, and whether the target range is the minimum measuring range of all measuring ranges of the second current value or not. If the second current value is outside the target range of the adjustable range measuring unit, or the target range is not the minimum measuring range of all measuring ranges of the second current value, it represents that the second current value at this time is inaccurate, or the second current value can be measured by using a smaller measuring range of the adjustable range measuring unit, so as to obtain a more accurate value, so that the second current value at this time is not output, but the range selection switch corresponding to the first resistor is closed again.

If the second current value is within the target range of the adjustable range measuring unit and the target range is the minimum measuring range of all measuring ranges of the second current value, the second current value is output because the second current value measured at the moment is the most accurate value which can be measured by the current measuring device.

The device can automatically switch the measuring range according to the current signal to be measured, the current signal to be measured does not exceed the minimum measuring range of the measuring range, and the device can measure the most accurate measuring range of the current signal to be measured. Therefore, the measuring range can be automatically switched to the optimal measuring range according to the current signal to be measured, the measuring accuracy is guaranteed, when the plurality of range selection switches are switched to the closed range selection switches, the second voltage value measured by the adjustable range measuring unit is inaccurate, at the moment, the processor determines and outputs the current value corresponding to the current signal to be measured according to the first voltage value, and the continuity and the accuracy of the current measurement can be still maintained under the condition that the measuring result of the adjustable range measuring unit is inaccurate.

Illustratively, the maximum measuring range of the adjustable-range measuring unit is equal to the measuring range of the maximum measuring range measuring unit, and the second maximum measuring range of the adjustable-range measuring unit is the measuring range next to the maximum measuring range from the plurality of measuring ranges of the adjustable-range measuring unit.

Taking fig. 1 as an example, the range changeover switch 20 corresponding to the measurement range of the maximum range measurement unit is the same as the range changeover switch 20 corresponding to the first resistor 11. When the range switch 20 corresponding to the first resistor 11 is closed, the adjustable range measuring unit only measures the voltage formed on the first resistor 11, and the current value corresponding to the current signal to be measured can reach the maximum value, that is, the measuring range of the adjustable range measuring unit is the maximum measuring range at this time.

The range change-over switch 20 corresponding to the second large measuring range of the adjustable range measuring unit is the same as the range change-over switch 20 corresponding to the sampling resistor 10 connected with the first resistor 11. When the range switch 20 corresponding to the sampling resistor 10 connected to the first resistor 11 is closed, the adjustable range measuring unit measures the voltage formed on the sampling resistor 10 connected to the first resistor 11 and the first resistor 11, and the current value corresponding to the current signal to be measured can reach the second maximum value, that is, the measurement range of the adjustable range measuring unit is the second maximum measurement range.

Assuming that the measuring range of the maximum measuring range measuring unit is 5A, and the measuring range of the adjustable measuring range measuring unit includes 5A grade, 3A grade, 1.5A grade and the like, the measuring range of the adjustable measuring range measuring unit is 5A grade, and the measuring range of the adjustable measuring range measuring unit is the second large measuring range which is 3A grade.

In one embodiment, the processor 50 is further configured to, when the second voltage value gradually increases, take the first upper scale limit as the upper scale limit and the first lower scale limit as the lower scale limit; and when the second voltage value is gradually reduced, taking the second proportion upper limit as the proportion upper limit, taking the second proportion lower limit as the proportion lower limit, wherein the second proportion upper limit is smaller than the first proportion upper limit, and the second proportion lower limit is smaller than the first proportion lower limit.

Taking fig. 4 as an example, Vth1+ represents a first upper ratio limit, Vth0+ represents a second upper ratio limit, Vth 0-represents a first lower ratio limit, and Vth 1-represents a second lower ratio limit. As shown in fig. 4, the first upper ratio limit Vth1+ is greater than the second upper ratio limit Vth0+, and the first lower ratio limit Vth 0-is greater than the second lower ratio limit Vth 1-.

The arrows in fig. 4 represent the trend of the voltage change, and the solid line indicates the selected upper or lower proportional limit.

When the second voltage value gradually increases, the first upper scale limit Vth1+ is selected as the upper scale limit as shown in the upper left diagram in fig. 4, and the first lower scale limit Vth 0-is selected as the lower scale limit as shown in the lower right diagram in fig. 4.

When the second voltage value gradually decreases, as shown in the upper right diagram in fig. 4, the second upper scale limit Vth0+ is selected as the upper scale limit, and as shown in the lower left diagram in fig. 4, the second lower scale limit Vth 1-is selected as the lower scale limit.

Specifically, the second voltage value gradually increases, that is, the second voltage value at the next time is greater than the second voltage value at the previous time within the set time period. The second voltage value gradually decreases, that is, the second voltage value at the next moment is smaller than the second voltage value at the previous moment in the set time length.

Illustratively, the processor 50 includes a hysteresis comparator for changing the upper scale limit of the processor 50 to a first upper scale limit and the lower scale limit to a first lower scale limit when the voltage value is gradually increased, and changing the upper scale limit of the processor 50 to a second upper scale limit and the lower scale limit to a second lower scale limit when the voltage value is gradually decreased.

Illustratively, the first upper proportion limit, the first lower proportion limit, the second upper proportion limit and the second lower proportion limit are determined according to an actual noise value of the current signal to be measured.

In this embodiment, when the voltage value gradually increases, the upper proportional limit and the lower proportional limit of the processor are changed to the first upper proportional limit and the first lower proportional limit, and when the voltage value gradually decreases, the upper proportional limit and the lower proportional limit of the processor are changed to the second upper proportional limit and the second lower proportional limit, respectively. The first upper proportion limit, the first lower proportion limit, the second upper proportion limit and the second lower proportion limit are determined according to an actual noise value. Therefore, when the voltage value acquired by the analog-to-digital converter is noisy, the voltage fluctuation caused by the noise can be covered by the hysteresis width, so that the influence of the noise on the judgment of the processor on whether the second analog-to-digital converter exceeds the measuring range is avoided, the current value output by the processor is frequently replaced and selected due to the influence of the noise, and the current value output by the processor is more stable.

In one embodiment, as shown in fig. 5, the device further comprises at least one short-circuit switch 21. At least one short-circuit switch 21 is in one-to-one correspondence with the sampling resistors 10, the first end of the short-circuit switch is connected with the first end of the corresponding sampling resistor 10, and the second end of the short-circuit switch is connected with the input end of the second operational amplifier 31 connected with the second end of the second resistor 12, and is used for being closed when the corresponding range selection switch 20 is closed.

In this embodiment, by setting the short-circuit switch, when the corresponding sampling resistor is not connected to the measurement branch, the sampling resistor is short-circuited. Therefore, the phenomenon that the line parasitic capacitance of the sampling resistor reduces the line bandwidth of the measuring branch circuit is avoided, and the measuring sensitivity is higher.

In one embodiment, as shown in fig. 6, there is provided a current measuring method including the steps of:

s502, the current signal to be measured passes through the pass switching circuit.

Specifically, the range switching circuit comprises a plurality of sampling resistors and a plurality of range selection switches which are in one-to-one correspondence; the sampling resistors are connected in series, the sampling resistors at two ends are respectively a first resistor and a second resistor, and one end of each sampling resistor, which is close to the first resistor or far away from the second resistor, is a first end; the first end of each range selection switch is connected with the second end of the corresponding sampling resistor, and the second ends of the range selection switches are connected together; the first end of the first resistor and the second ends of the plurality of range selection switches are the input end and the output end of the current signal to be measured in the range switching circuit.

S504, at least one of the plurality of span select switches is closed.

S506, measuring the voltage formed by the current signal to be measured on the first resistor through the first operational amplifier, generating a voltage measurement signal and scaling the voltage measurement signal.

And S508, measuring the voltage measurement signal obtained by scaling the first operational amplifier through the first analog-to-digital converter to obtain a first voltage value. The first operational amplifier and the first analog-to-digital converter are connected to form a maximum measuring range measuring unit.

And S510, measuring the voltage formed by the current signal to be measured on the plurality of sampling resistors through a second operational amplifier, generating a voltage measurement signal and scaling the voltage measurement signal.

And S512, measuring the amplified voltage signal of the second operational amplifier after being scaled through the second analog-to-digital converter to obtain a second voltage value. The second operational amplifier and the second analog-to-digital converter are connected to form an adjustable range measuring unit

And S514, when the range selection switch corresponding to the first resistor is closed, determining a target range of the adjustable range measuring unit based on the first voltage value, wherein the target range corresponds to one of the range selection switches, and the measuring range of the adjustable range measuring unit when the range selection switch corresponding to the target range is closed is the target range.

S516, within the first set duration after the target range is determined, the range selection switch corresponding to the target range is closed.

S518, between the first set time length and the second set time length after the target range is determined, all the range selection switches except the range selection switch corresponding to the target range are turned off.

And S520, determining a first current value corresponding to the current signal to be measured and outputting the first current value based on the first voltage value in a second set time length after the target measuring range is determined.

In this embodiment, a range switching circuit is composed of a plurality of sampling resistors and a plurality of range selection switches in one-to-one correspondence, the plurality of sampling resistors are connected in series, the sampling resistors at two ends are respectively a first resistor and a second resistor, one end of each sampling resistor, which is close to the first resistor or is far away from the second resistor, is a first end, the first end of each range selection switch is connected with the second end of the corresponding sampling resistor, the second ends of the plurality of range selection switches are connected together, at least one of the plurality of range selection switches is closed, and the first end of the first resistor and the second ends of the plurality of range selection switches are input ends and output ends of current signals to be measured. In this way, the current signal to be measured only passes through the sampling resistor between the first resistor and the sampling resistor corresponding to the closed range selection switch, and the sampling resistor between the sampling resistor corresponding to the closed range selection switch and the second resistor is short-circuited. The quantity of sampling resistors through which current signals to be measured pass can be changed by selecting different range selection switches to be closed, so that the size of the resistor through which the current signals to be measured pass is changed, and the voltage formed by the current signals to be measured on the sampling resistors is controlled within the measuring range of the measuring unit under the condition that the current signals to be measured are different in size, so that the measuring unit can accurately measure the voltage.

The method comprises the steps of connecting a first operational amplifier and a first analog-to-digital converter to form a maximum measuring range measuring unit, connecting the first operational amplifier to a first end and a second end of a first resistor respectively, measuring the voltage formed by a current signal to be measured on the first resistor, generating a voltage measuring signal and scaling the voltage measuring signal, and measuring the scaled voltage measuring signal of the first operational amplifier by the first analog-to-digital converter to obtain a first voltage value. Since the maximum range measuring unit measures only the voltage formed on one resistor of the first resistor, the maximum range measuring unit can realize measurement within the maximum range.

And the second analog-to-digital converter measures the voltage measurement signal of the second operational amplifier after being scaled to obtain a second voltage value. Because the voltage formed on the sampling resistors is determined by the closed range selection switch, and the closed range selection switch can be selected according to the size of the current signal to be measured so as to control the voltage formed on the sampling resistors within the measurement range of the measurement unit, the measurement range of the adjustable range measurement unit can be adjusted to be matched with the current signal to be measured, and the accurate measurement within a small range is realized.

When the range selection switch corresponding to the first resistor is closed, the target range of the adjustable range measuring unit is determined according to the first voltage value, the range selection switch corresponding to the target range is closed within the first set duration after the target range is determined, all range selection switches except the range selection switch corresponding to the target range are opened between the first set duration and the second set duration after the target range is determined, automatic switching of the measuring range of the adjustable range measuring unit can be achieved, at least one of the range switching switches is closed in the range switching process in the measuring range switching process, and the maximum range measuring unit can perform accurate measurement. In the process of switching the measuring range, the second voltage value measured by the adjustable measuring range measuring unit is inaccurate. And in a second set time length after the target range is determined, determining and outputting a first current value corresponding to the current signal to be measured based on the first voltage value, so that the continuity and the accuracy of the current measurement can be still maintained under the condition that the measurement result of the adjustable range measurement unit is inaccurate.

It should be understood that, although the steps in the flowcharts of fig. 2, 3 and 6 are shown in sequence as indicated by the arrows, the steps are not necessarily performed in sequence as indicated by the arrows. The steps are not performed in the exact order shown and described, and may be performed in other orders, unless explicitly stated otherwise. Moreover, at least a portion of the steps in fig. 2, 3, and 6 may include multiple steps or multiple stages, which are not necessarily performed at the same time, but may be performed at different times, which are not necessarily performed in sequence, but may be performed alternately or alternately with other steps or at least a portion of the steps or stages in other steps.

It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by hardware instructions of a computer program, which can be stored in a non-volatile computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. Any reference to memory, storage, database or other medium used in the embodiments provided herein can include at least one of non-volatile and volatile memory. Non-volatile Memory may include Read-Only Memory (ROM), magnetic tape, floppy disk, flash Memory, optical storage, or the like. Volatile Memory can include Random Access Memory (RAM) or external cache Memory. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM), among others.

In the description herein, references to the description of "some embodiments," "other embodiments," "desired embodiments," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, a schematic description of the above terminology may not necessarily refer to the same embodiment or example.

The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.