CN114062764A - Direct current small current measuring system and method based on standard current - Google Patents
Direct current small current measuring system and method based on standard current Download PDFInfo
- Publication number
- CN114062764A CN114062764A CN202111369983.2A CN202111369983A CN114062764A CN 114062764 A CN114062764 A CN 114062764A CN 202111369983 A CN202111369983 A CN 202111369983A CN 114062764 A CN114062764 A CN 114062764A
- Authority
- CN
- China
- Prior art keywords
- signal
- current
- output
- resistor
- standard
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Measurement Of Current Or Voltage (AREA)
Abstract
The invention discloses a standard current-based direct current small current measuring system and method, wherein a digital processing circuit, a voltage conversion circuit and a sampling resistor are added on the basis of the existing single-magnetic-core magnetic modulation type leakage current detection, and the digital processing circuit is used for summing V generated by a following output circuit1/V1TThe analog voltage signal is subjected to digital calculation processing, and the output can reflect the measured current signal IP. The digital processing circuit outputs a standard voltage signal VTVoltage conversion circuit for VTConverting to output standard current signal IT，ITPassing through a current transformer and a measured current signal IPCurrent superposition, following the output voltage signal V by summation1TTo a digital processing circuit while I is being suppliedTOutputting to a sampling resistor; the sampling resistor is used for pair ITSampling and converting into a voltage signal V2And returning to the digital processing circuit. The invention can realize direct current leakage current signal by using a standard current signal feedback modeAnd (5) detecting with high precision.
Description
Technical Field
The invention relates to the technical field of current detection, in particular to a direct current small current measuring system and method based on standard current.
Background
In modern electronic power equipment, the condition of direct current insulation needs to be monitored in real time, and the leakage current of the insulation direct current is generally dozens of mA to hundreds of mA. There are many methods for detecting the dc leakage current, including an electromagnetic induction method, a hall effect method, a magneto-optical effect, a photoelectric effect method, and the like. However, since the dc leakage current to be measured is a small dc difference signal, for the purpose of accurate measurement, an electromagnetic induction method is usually used for the measurement, and a common test method is based on a magnetic modulation principle, such as: phase difference magnetic modulation, frequency doubling magnetic modulation, and the like. There are also a variety of test methods for leakage current testing on the magnetic modulation principle, including: based on double iron cores and single iron cores, the single iron core structure is relatively easy to manufacture and low in cost, and is suitable for batch popularization.
However, in the existing system and method for measuring a direct current signal based on a magnetic modulation and demodulation technology, because the test current is small, the test accuracy of the direct current leakage current is not high due to the influences of the installation position, the environmental temperature, the geomagnetic field and the like, the output change is large, and the field test requirements cannot be met.
Disclosure of Invention
The invention aims to solve the technical problems that the existing direct current signal measuring system and method based on the magnetic modulation and demodulation technology has low direct current leakage current measuring precision and large output change due to the influence of a mounting position, environmental temperature, a geomagnetic field and the like because of small measuring current, and can not meet the field test requirement.
The invention aims to provide a direct current small current measuring system and a direct current small current measuring method based on standard current, and the direct current small current measuring system and the direct current small current measuring method mainly aim at direct current small current measurement, and the measuring range is dozens of mA-hundreds of mA; the invention adds a standard current generating circuit on the basis of the existing single-magnetic-core magnetic modulation type leakage current detection, relates to a voltage conversion circuit, a digital processing circuit, a high-precision resistor and zero point correction, is used for compensating the product zero point and rated output change caused by the change of position, environment, geomagnetic field and the like, and finally realizes stable high-precision detection of direct current leakage current signals.
The invention is realized by the following technical scheme:
in a first aspect, the present inventionThe measuring system comprises a current transformer, a square-wave oscillator, an infinite gain filter, a proportional amplifier and a summation following output circuit which are connected in sequence, wherein the current transformer is connected with a current signal (a measured direct current signal I)pAnd a standard current signal IT) (ii) a DC signal I to be measuredpAnd a standard current signal ITThe current transformer is connected into a square wave oscillator for modulation to obtain a modulation signal, the modulation signal is demodulated and amplified through an infinite gain filter and proportional amplification, and then the modulation signal is sent to a summation following output circuit to generate V1/V1TSimulating a voltage signal; the system also comprises a digital processing circuit, a voltage conversion circuit and a sampling resistor, wherein the output end of the summation following output circuit is connected with the digital processing circuit, the digital processing circuit is connected with the voltage conversion circuit, the voltage conversion circuit outputs a standard current signal to pass through the current transformer, the output standard current signal is subjected to voltage sampling through the sampling resistor, and the sampled voltage is fed back to the digital processing circuit;
the digital processing circuit has three functions: first, it generates the standard voltage signal VT，VTGenerating a standard current signal I by a voltage conversion circuitT，ITIs sampled and converted into a voltage signal V by a sampling resistor R2Is sent back to the digital processing circuit, passes through and VTComparing and judging the standard current signal ITThe accuracy of (2); secondly, the voltage signal V containing the detected current signal output by the summation following output circuit1And a voltage signal V containing the measured current signal and the standard current1TCalculating and processing to finally output a signal I capable of reflecting the measured currentPThe output signal of (1); thirdly, the zero correction algorithm processing is contained in the product, and a user can carry out output zero correction on the product under the condition of no external input signal through a zero correction external interface;
the voltage conversion circuit is used for converting the standard voltage signal V generated by the digital processing circuitTConverting to output standard current signal IT，ITOn the one hand with the measured current signal IPSuperposed and fed into current transformer to make summation follow-up output become V1T(ii) a On the other hand ITSampling and converting the voltage signal into a voltage signal V through a sampling resistor2Returning to the digital processing circuit;
the sampling resistor is used for sampling a standard current signal ITSampling and converting into a voltage signal V2And returning to the digital processing circuit to judge the accuracy of the standard current signal.
The invention mainly aims at the direct current small current measurement, and the measurement range is dozens of mA-hundreds of mA; on the basis of the existing single-magnetic-core magnetic modulation type leakage current detection, the invention adds a standard current generation circuit, relates to a voltage conversion circuit, a digital processing circuit and zero point correction, is used for compensating product zero point and rated output changes caused by changes of positions, environments, geomagnetic fields and the like, and finally realizes stable high-precision detection of a direct current leakage current signal. Specifically, the method comprises the following steps: on the one hand, the DC signal I to be measuredpThe current transformer is connected into a square wave oscillator for modulation, then the modulated signal is demodulated and amplified through an infinite gain filter and proportional amplification, and then the modulated signal is sent to a summation following output circuit to generate V1The analog voltage signal is sent to the AD port of the CPU of the digital processing circuit. On the other hand, the digital processing circuit itself outputs a standard voltage signal VTConverting the voltage V into the current I through the voltage conversion to output the standard current IT，ITSent into a current transformer and a measured current signal IPPerforming superposition to change the input DC current signal to Ip+IT(ii) a At the same time ITConversion to V by high-precision sampling resistor R2Returning to the digital processing circuit, the digital processing circuit CPU internally passing through and VTThe standard comparison monitors the accuracy of the output standard voltage. Superimposed direct current signal Ip+ITThe voltage signal is processed by a current transformer, a square wave oscillator is connected again, and the voltage signal is processed into V through circuits such as modulation, demodulation amplification, summation following and the like1TAnd the signal is sent to an AD port of a CPU of the digital processing circuit. Voltage value V is output twice before and after current standard is increased in digital processing circuit1、VITSolving quadratic equationVarious influences are eliminated through final calculation, and the output can reflect the measured direct current signal IPMagnitude output signal.
Further, the digital processing circuit is used for summing a voltage signal V containing the measured current signal output by the following output circuit1And a voltage signal V containing the measured current signal and the standard current1TCalculating and processing to finally output a signal I capable of reflecting the measured currentPThe output signal of (1); during calculation, the integral gain K of the digital processing circuit before and after the current standard is increased, and the influence delta T of the environment, the position and the electromagnetic field are unchanged; measured direct current signal IPThe calculation formula is as follows:
V1＝IP*K*(1+ΔT) (1)
V1T＝(IP+IT)*K*(1+ΔT) (2)
in the formula, K is the integral gain of the proportional amplifying circuit, and delta T is the influence factors of environment, position and electromagnetic field;
V1、V1T、ITare known numbers, and the direct current I to be measured can be calculated by combining the formulas (1) and (2)PMagnitude of, measured current signal IPThe calculation formula is as follows:
IP＝V1IT/(V1T-V1) (3)
where the measured current signal I is outputPIs not affected by Δ T.
Further, the output signal can realize accurate measurement of the measured direct current signal, but the direct current signal superposes a zero point error, so that the output changes along with the change of the zero point. Therefore, the system is additionally provided with a zero point correction circuit, the zero point correction circuit is connected with the output end of the digital processing circuit, the deviation under the condition that the detected current signal is not added is calculated through the digital processing circuit, the zero point correction circuit carries out processing through a zero point correction algorithm, the output zero point is corrected, and the final output signal can accurately reflect the size of the input detected direct current signal.
Further, the main purpose of the voltage conversion circuit is to generate a standard voltage signal V to the CPU of the digital processing circuitTPerforming V/I conversion to obtain standard current signal ITOn one hand, the standard current signal is sent into a current transformer for current superposition, and on the other hand, the standard current signal is sampled and converted into a voltage signal V through a high-precision sampling resistor R2And returning to the CPU of the digital processing circuit for judging the accuracy of the output standard voltage signal. The voltage conversion circuit is shown in fig. 2. In the figure, in order to ensure the accuracy of the standard voltage signal, the sampling resistor R needs to adopt a high-precision low-temperature drift resistor.
The voltage conversion circuit comprises a power supply VCC, an amplifier NIA, an amplifier NIB, a resistor R1, a resistor R2, a resistor R3, a resistor R4 and a resistor R5; compared with the traditional V/I conversion circuit, the circuit can stably output the current I by introducing positive and negative feedbackTMoreover, the anti-interference capability of the whole circuit can be improved by introducing the operational amplifier N1B;
one end of the resistor R1 is connected with a standard voltage signal VTThe other end of the resistor R2 is connected with the first input end of an amplifier NIA, the second input end of the amplifier NIA is connected with one end of a resistor R2, and the other end of the resistor R2 is grounded; the output end of the amplifier NIA is connected with one end of the resistor R4/R5, the other end of the resistor R4 is connected with the first input end of the amplifier NIB, the second input end of the amplifier NIB is connected with one end of the resistor R3, the output end of the amplifier NIB is also connected with one end of the resistor R3, and the other end of the resistor R3 is connected with the common end of the resistor R1 and the first input end of the amplifier NIA;
the positive electrode of the power supply VCC is connected with the first input end of the amplifier NIA, the negative electrode of the power supply VCC is connected with the second input end of the amplifier NIA, and the positive electrode and the negative electrode of the power supply VCC are grounded through capacitors;
one end of the resistor R5 is connected with the common end of the resistor R2 and the second input end of the amplifier NIA, and the other end is connected with the output end of the amplifier NIA and the common end of the resistor R4; the output end of the resistor R4 is used as an output standard current signal IT(ii) a The output standard current signal ITIs converted into V by sampling through a high-precision sampling resistor R2And returning to the digital processing circuit.
Furthermore, the sampling resistor is a high-precision low-temperature drift resistor.
Furthermore, the measuring system adopts positive and negative feedback and the operational amplifier N1B to follow the output, and compared with the traditional voltage conversion circuit, the measuring system can quickly generate a stable standard current signal ITAnd the circuit stability and reliability are high.
In a second aspect, the present invention further provides a dc small current measuring method based on standard current, which is applied to the dc small current measuring system based on standard current, and the method includes:
DC signal I to be measuredpA current transformer is connected into a square wave oscillator for modulation to obtain a modulation signal;
demodulating and amplifying the modulation signal by using an infinite gain filter and proportional amplification, and then sending the demodulation amplified modulation signal to a summation following output circuit to generate V1Simulating a voltage signal;
generating a reference voltage signal V using a digital processing circuitTConverted into standard current signal I by voltage conversion circuitTSent to a current transformer to be measured with a DC current signal IPPerforming superposition to superpose the standard current signal ITThe output waveform of the square wave oscillator is changed by the current transformer, so that the voltage signal output by the final summation follower is changed into V1T；
Using digital processing circuit to sum voltage signal V generated by following output circuit1/V1TCarrying out digital calculation processing, wherein the finally output signal can reflect the magnitude of the measured current signal;
meanwhile, a sampling resistor R is adopted to carry out comparison on a reference current signal ITSampling and converting into a voltage signal V2Returning to the digital processing circuit to output standard current signal ITAnd (6) judging the accuracy.
Further, the voltage signal V generated by the summing following output circuit is processed by a digital processing circuit1/V1TCarrying out digital calculation processing, wherein the finally output signal can reflect the magnitude of the measured current signal; when calculating, the current is increasedThe integral gain K of the proportional amplifying circuit before and after the standard and the influence delta T of the environment, the position and the electromagnetic field are unchanged; measured direct current signal IPThe calculation formula is as follows:
V1＝IP*K*(1+ΔT) (1)
V1T＝(IP+IT)*K*(1+ΔT) (2)
in the formula, K is the integral gain of the proportional amplifying circuit, and delta T is the influence factors of environment, position and electromagnetic field;
V1、V1T、ITare known numbers, and the direct current I to be measured can be calculated by combining the formulas (1) and (2)PSee the following equation (3):
IP＝V1IT/(V1T-V1) (3)
in the formula IPIs the measured current signal.
Where the measured current signal I is outputPIs not affected by Δ T.
And furthermore, the method also comprises zero point correction, and the measurement method corrects the output zero point through the output end of the digital processing circuit before the test, so that the influence of factors such as installation, environment and the like is completely eliminated, and the final output signal can accurately reflect the size of the input tested direct current signal.
Furthermore, the sampling resistor is a high-precision low-temperature drift resistor.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. compared with the traditional magnetic modulation type leakage current detection system and method, the invention innovatively introduces the voltage conversion circuit, the digital processing circuit and the zero correction circuit, realizes that the output does not change along with the changes of the installation position of a product, the environmental temperature, the geomagnetic field and the like, and can truly reflect the magnitude of the detected direct current.
2. Compared with the traditional magnetic modulation type leakage current detection system and method, the invention can greatly improve the response time of the product by introducing the standard current and the digital processing scheme.
3. Compared with the traditional magnetic modulation type leakage current detection system and method, the invention has no strict requirements on the size and direction of the introduced standard current signal and has stronger operability.
4. Compared with the traditional magnetic modulation type leakage current detection system and method, the invention realizes the generation of the standard signal by introducing the CPU (central processing unit) of the digital processing circuit, reduces the requirement on the output capability of the circuit, and has higher accuracy and stronger stability of the output voltage signal.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:
fig. 1 is a schematic structural diagram of a dc small current measurement system based on a standard current according to the present invention.
FIG. 2 is a schematic diagram of a voltage conversion circuit according to the present invention.
Detailed Description
Hereinafter, the term "comprising" or "may include" used in various embodiments of the present invention indicates the presence of the invented function, operation or element, and does not limit the addition of one or more functions, operations or elements. Furthermore, as used in various embodiments of the present invention, the terms "comprises," "comprising," "includes," "including," "has," "having" and their derivatives are intended to mean that the specified features, numbers, steps, operations, elements, components, or combinations of the foregoing, are only meant to indicate that a particular feature, number, step, operation, element, component, or combination of the foregoing, and should not be construed as first excluding the existence of, or adding to the possibility of, one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing.
In various embodiments of the invention, the expression "or" at least one of a or/and B "includes any or all combinations of the words listed simultaneously. For example, the expression "a or B" or "at least one of a or/and B" may include a, may include B, or may include both a and B.
Expressions (such as "first", "second", and the like) used in various embodiments of the present invention may modify various constituent elements in various embodiments, but may not limit the respective constituent elements. For example, the above description does not limit the order and/or importance of the elements described. The foregoing description is for the purpose of distinguishing one element from another. For example, the first user device and the second user device indicate different user devices, although both are user devices. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of various embodiments of the present invention.
It should be noted that: if it is described that one constituent element is "connected" to another constituent element, the first constituent element may be directly connected to the second constituent element, and a third constituent element may be "connected" between the first constituent element and the second constituent element. In contrast, when one constituent element is "directly connected" to another constituent element, it is understood that there is no third constituent element between the first constituent element and the second constituent element.
The terminology used in the various embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the various embodiments of the invention. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments of the present invention belong. The terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning that is consistent with their contextual meaning in the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein in various embodiments of the present invention.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
Example 1
As shown in figures 1 and 2, the direct current small current measuring system based on the standard current comprises a current transformer, a square wave oscillator, an infinite gain filter, a proportional amplifier and a summation following output circuit which are connected in sequence, wherein the current transformer is connected to a direct current signal I to be measuredp(ii) a DC signal I to be measuredpThe current transformer is connected into a square wave oscillator for modulation to obtain a modulation signal, the modulation signal is demodulated and amplified through an infinite gain filter and proportional amplification, and then the modulation signal is sent to a summation following output circuit to generate V1Simulating a voltage signal; the system also comprises a digital processing circuit, a voltage conversion circuit and a sampling resistor, wherein the output end of the summation following output circuit is connected with the digital processing circuit, and the digital processing circuit outputs a standard voltage signal VTConnected with a voltage conversion circuit which outputs a standard current signal I by V/I conversionTPassing through a current transformer; standard current signal ITAnd is converted into voltage V by resistance sampling via sampling resistor2Returning to the digital processing circuit;
the digital processing circuit internally generates a standard voltage signal VT(ii) a The standard voltage signal V is converted by a voltage conversion circuitTConversion into a standard current signal ITSent into a current transformer and a measured current signal IpPerforming superposition to change the input DC current signal to Ip+IT. Superimposed direct current signal Ip+ITThe voltage signal is processed by a current transformer, a square wave oscillator is connected again, and the voltage signal is processed into V through circuits such as modulation, demodulation amplification, summation following and the like1TSending the data to a digital processing circuit; and V generated by summing following output circuit1/V1TThe analog voltage signal is subjected to digital calculation processing, and is subjected to combined solution to output and measured direct current signal IPAn equivalent output signal;
the voltage conversion circuit is used for converting the standard voltage signal V generated by the digital processing circuitTConverting voltage to current to output standard current signalITOn the one hand, the standard current signal ITPassing through a current transformer and a measured current signal IPCurrent superposition is carried out, and finally the summation follows the output voltage signal V1TTo a digital processing circuit; on the other hand the standard current signal ITSampling and converting the voltage signal into a voltage signal V through a sampling resistor2Returning to the digital processing circuit;
the sampling resistor is used for sampling a standard current signal ITSampling and converting into a voltage signal V2And returning to the digital processing circuit for judging the accuracy of the output standard current signal.
In this embodiment, the digital processing circuit is used for summing the voltage signal V containing the measured current signal output by the following output circuit1And a voltage signal V containing the measured current signal and the standard current1TCalculating and processing to finally output a signal I capable of reflecting the measured currentPThe output signal of (1); during calculation, the integral gain K of the digital processing circuit before and after the current standard is increased, and the influence delta T of the environment, the position and the electromagnetic field are unchanged; measured direct current signal IPThe calculation formula is as follows:
V1＝IP*K*(1+ΔT) (1)
V1T＝(IP+IT)*K*(1+ΔT) (2)
in the formula, K is the integral gain of the proportional amplifying circuit, and delta T is the influence factors of environment, position and electromagnetic field;
V1、V1T、ITare known numbers, and the direct current I to be measured can be calculated by combining the formulas (1) and (2)PMagnitude of, measured current signal IPThe calculation formula is as follows:
IP＝V1IT/(V1T-V1) (3)
where the measured current signal I is outputPIs not affected by Δ T.
In this embodiment, the output signal can realize accurate measurement of the dc signal to be measured, but the dc signal itself is superimposed with a zero point error, which results in that the output changes with the change of the zero point. Therefore, the system is additionally provided with a zero point correction circuit, the zero point correction circuit is connected with the output end of the digital processing circuit, the deviation under the condition that the detected current signal is not added is calculated through the digital processing circuit, the zero point correction circuit carries out processing through a zero point correction algorithm, the output zero point is corrected, and the final output signal can accurately reflect the size of the input detected direct current signal.
The zero point correction circuit is mainly designed to eliminate output change caused by zero point change in output signals, and the zero point correction method is realized through digital processing circuit software design. Finally, through the current standard, digital processing and zero correction, the output signal can accurately and effectively reflect the measured direct current signal IPThe size of (2).
In this embodiment, the main purpose of the voltage conversion circuit is to generate a standard voltage signal V for the CPU of the digital processing circuitTPerforming V/I conversion to obtain standard current signal ITOn one hand, the standard current signal is sent into a current transformer for current superposition, and on the other hand, the standard current signal is sampled and converted into a voltage signal V through a sampling resistor R2And returning to the CPU of the digital processing circuit for judging the accuracy of the output standard voltage signal. The voltage conversion circuit is shown in fig. 2. In the figure, in order to ensure the accuracy of the standard current signal, the sampling resistor R needs to adopt a high-precision low-temperature drift resistor. The voltage conversion circuit comprises a power supply VCC, an amplifier NIA, an amplifier NIB, a resistor R1, a resistor R2, a resistor R3, a resistor R4 and a resistor R5; compared with the traditional V/I conversion circuit, the circuit can stably output the current I by introducing positive and negative feedbackTMoreover, the anti-interference capability of the whole circuit can be improved by introducing the operational amplifier N1B;
one end of the resistor R1 is connected with a standard voltage signal VTThe other end of the resistor R2 is connected with the first input end of an amplifier NIA, the second input end of the amplifier NIA is connected with one end of a resistor R2, and the other end of the resistor R2 is grounded; the output end of the amplifier NIA is connected with one end of the resistor R4/R5, the other end of the resistor R4 is connected with the first input end of the amplifier NIB, and the amplifierThe second input end of the NIB is connected with one end of the resistor R3, the output end of the amplifier NIB is also connected with one end of the resistor R3, and the other end of the resistor R3 is connected with the common end of the resistor R1 and the first input end of the amplifier NIA;
the positive electrode of the power supply VCC is connected with the first input end of the amplifier NIA, the negative electrode of the power supply VCC is connected with the second input end of the amplifier NIA, and the positive electrode and the negative electrode of the power supply VCC are grounded through capacitors;
one end of the resistor R5 is connected with the common end of the resistor R2 and the second input end of the amplifier NIA, and the other end is connected with the output end of the amplifier NIA and the common end of the resistor R4; the output end of the resistor R4 is used as an output standard current signal IT(ii) a The output ITIs converted into V by sampling through a sampling resistor R2And returning to the digital processing circuit.
The working principle is as follows: the invention mainly aims at the direct current small current measurement, and the measurement range is dozens of mA-hundreds of mA; the invention adds a standard current generating circuit on the basis of the existing single-magnetic-core magnetic modulation type leakage current detection, relates to a voltage conversion circuit, a digital processing circuit and a zero point correction circuit, and is used for compensating the product zero point and rated output change caused by the change of position, environment, geomagnetic field and the like, and finally realizing stable high-precision detection of a direct current leakage current signal. Specifically, the method comprises the following steps: on the one hand, the DC signal I to be measuredpThe current transformer is connected into a square wave oscillator for modulation, then the modulated signal is demodulated and amplified through an infinite gain filter and proportional amplification, and then the modulated signal is sent to a summation following output circuit to generate V1The analog voltage signal is sent to the AD port of the CPU of the digital processing circuit. On the other hand, the digital processing circuit itself outputs a standard voltage signal VTConverting the voltage V into the current I through the voltage conversion to output the standard current IT，ITSending into a current transformer to change the input DC signal to Ip+IT(ii) a At the same time ITConversion to V by high-precision sampling resistor R2Returning to the digital processing circuit, the digital processing circuit CPU internally passing through and VTThe standard comparison monitors the accuracy of the output standard voltage. Superimposed direct current signal Ip+ITPasses through the electricity againThe current transformer is connected into a square wave oscillator, and output voltage signals are processed into V through circuits such as modulation, demodulation amplification, summation following and the like1TAnd the signal is sent to an AD port of a CPU of the digital processing circuit. Voltage value V is output twice before and after current standard is increased in digital processing circuit1、VITSolving a quadratic equation, eliminating various influences through final calculation, and outputting a direct current signal I capable of reflecting the measured direct currentPMagnitude output signal.
The invention has the following innovation points:
1) compared with the traditional magnetic modulation type leakage current detection system and method, the invention innovatively introduces the voltage conversion circuit, the digital processing circuit and the zero correction circuit, realizes that the output does not change along with the changes of the installation position of a product, the environmental temperature, the geomagnetic field and the like, and can truly reflect the magnitude of the detected direct current.
2) Compared with the traditional magnetic modulation type leakage current detection system and method, the invention can greatly improve the response time of the product by introducing the standard current and the digital processing scheme.
3) Compared with the traditional magnetic modulation type leakage current detection system and method, the invention has no strict requirements on the size and direction of the introduced standard current signal and has stronger operability.
4) Compared with the traditional magnetic modulation type leakage current detection system and method, the invention realizes the generation of the standard signal by introducing the CPU (central processing unit) of the digital processing circuit, reduces the requirement on the output capability of the circuit, and has higher accuracy and stronger stability of the output voltage signal.
Example 2
As shown in fig. 1 and fig. 2, the present embodiment is different from embodiment 1 in that the present embodiment provides a method for measuring a small direct current based on a standard current, which is applied to a system for measuring a small direct current based on a standard current described in embodiment 1, and the method includes:
DC signal I to be measuredpA current transformer is connected into a square wave oscillator for modulation to obtain a modulation signal;
applying the modulated signal using an infinite gain filter and proportional amplificationThe line demodulation, amplification, summation and following output circuit generates V1Simulating a voltage signal;
generating a reference voltage signal V using a digital processing circuitTConverted into standard current signal I by voltage conversion circuitTSent to a current transformer to be measured with a DC current signal IPPerforming superposition to superpose the standard current signal ITThe output waveform of the square wave oscillator is changed by the current transformer, so that the voltage signal output by the final summation follower is changed into V1T；
Using digital processing circuit to sum voltage signal V generated by following output circuit1/V1TCarrying out digital calculation processing, wherein the finally output signal can reflect the magnitude of the measured current signal;
meanwhile, a sampling resistor R is adopted to carry out comparison on a reference current signal ITSampling and converting into a voltage signal V2Returning to the digital processing circuit to output standard current signal ITAnd (6) judging the accuracy.
In this embodiment, the voltage signal V generated by the summing follower output circuit is processed by a digital processing circuit1/V1TCarrying out digital calculation processing, wherein the finally output signal can reflect the magnitude of the measured current signal; during calculation, the integral gain K of the proportional amplifying circuit before and after the current standard is increased, and the influence delta T of the environment, the position and the electromagnetic field are unchanged; measured direct current signal IPThe calculation formula is as follows:
V1＝IP*K*(1+ΔT) (1)
V1T＝(IP+IT)*K*(1+ΔT) (2)
in the formula, K is the integral gain of the proportional amplifying circuit, and delta T is the influence factors of environment, position and electromagnetic field;
V1、V1T、ITare known numbers, and the direct current I to be measured can be calculated by combining the formulas (1) and (2)PSee the following equation (3):
IP＝V1IT/(V1T-V1) (3)
in the formula IPIs the measured current signal.
Where the measured current signal I is outputPIs not affected by Δ T.
In the embodiment, the method also comprises zero point correction, and the measurement method corrects the output zero point through the output end of the digital processing circuit before the test, so that the influence of factors such as installation, environment and the like is completely eliminated, and the final output signal can accurately reflect the size of the input direct current signal to be measured.
The method mainly aims at direct current small current measurement, and the measurement range is dozens of mA-hundreds of mA; on the basis of the existing single-magnetic-core magnetic modulation type leakage current detection, the invention adds a standard current generation circuit, relates to a voltage conversion circuit, a digital processing circuit and zero point correction, and is used for compensating product zero point and rated output changes caused by changes of positions, environments, geomagnetic fields and the like, and finally realizing stable high-precision detection of a direct current leakage current signal.
The working process is as follows: on the one hand, the DC signal I to be measuredpThe current transformer is connected into a square wave oscillator for modulation, then the modulated signal is demodulated and amplified through an infinite gain filter and proportional amplification, and then the modulated signal is sent to a summation following output circuit to generate V1The analog voltage signal is sent to the AD port of the CPU of the digital processing circuit. On the other hand, the digital processing circuit itself outputs a standard voltage signal VTConverting the voltage V into the current I through the voltage conversion to output the standard current IT，ITSent into a current transformer and a measured current signal IPPerforming superposition to change the input DC current signal to Ip+IT(ii) a At the same time ITConversion to V by high-precision sampling resistor R2Returning to the digital processing circuit, the digital processing circuit CPU internally passing through and VTThe standard comparison monitors the accuracy of the output standard voltage. Superimposed direct current signal Ip+ITThe voltage signal is processed by a current transformer, a square wave oscillator is connected again, and the voltage signal is processed into V through circuits such as modulation, demodulation amplification, summation following and the like1TAnd the signal is sent to an AD port of a CPU of the digital processing circuit. Voltage value V is output twice before and after current standard is increased in digital processing circuit1、VITSolving a quadratic equation, eliminating various influences through final calculation, and outputting a direct current signal I capable of reflecting the measured direct currentPMagnitude output signal.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A direct current small current measuring system based on standard current comprises a current transformer, a square wave oscillator, an infinite gain filter, a proportional amplifier and a summation following output circuit which are connected in sequence, and is characterized in that the current transformer is connected with a current signal, the system also comprises a digital processing circuit, a voltage conversion circuit and a sampling resistor, the output end of the summation following output circuit is connected with the digital processing circuit, the digital processing circuit is connected with the voltage conversion circuit, the voltage conversion circuit outputs a standard current signal to pass through the current transformer, the output standard current signal also carries out voltage sampling through the sampling resistor, and the sampled voltage is fed back to the digital processing circuit;
the digital processing circuit is used for internally generating a standard voltage signal VT，VTGenerating a standard current signal I by a voltage conversion circuitT，ITIs sampled and converted into a voltage signal V by a sampling resistor R2Is sent back to the digital processing circuit, passes through and VTComparing and judging the standard current signal ITThe accuracy of (2); and a voltage signal V containing the current signal to be measured for the summation following output circuit1And a voltage signal V containing the measured current signal and the standard current1TCalculating and processing to finally output a signal I capable of reflecting the measured currentPThe output signal of (1);
the voltage conversion circuit is used for converting the standard voltage signal V generated by the digital processing circuitTConverting to output standard current signal IT，ITOn the one hand with the measured current signal IPSuperposed into a current transformer, on the other hand ITSampling and converting the voltage signal into a voltage signal V through a sampling resistor2Returning to the digital processing circuit;
the sampling resistor is used for sampling a standard current signal ITSampling and converting into a voltage signal V2And returning to the digital processing circuit to judge the accuracy of the standard current signal.
2. The standard current-based direct current small current measuring system according to claim 1, wherein the digital processing circuit is used for summing voltage signals V including measured current signals output by the following output circuit1And a voltage signal V containing the measured current signal and the standard current1TCalculating and processing to finally output a signal I capable of reflecting the measured currentPThe output signal of (1); wherein:
V1＝IP*K*(1+ΔT)
V1T＝(IP+IT)*K*(1+ΔT)
in the formula, K is the integral gain of the proportional amplifying circuit, and delta T is the influence factors of environment, position and electromagnetic field;
the magnitude of the measured direct current signal is calculated by combining the two formulas, and the calculation formula of the measured direct current signal is as follows:
IP＝V1IT/(V1T-V1)
in the formula IPIs the measured current signal.
3. The direct current small current measuring system based on the standard current as claimed in claim 1, further comprising a zero point calibration circuit, wherein the zero point calibration circuit is connected to the output end of the digital processing circuit, the deviation under the condition of no external measured current signal is calculated through the digital processing circuit, the zero point calibration algorithm is used for processing, the output zero point is calibrated, and the final output signal can accurately reflect the magnitude of the input measured direct current signal.
4. The standard current based DC small current measurement system according to claim 1, wherein the voltage conversion circuit comprises a power supply VCC, an amplifier NIA, an amplifier NIB, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5;
one end of the resistor R1 is connected with a standard voltage signal VTThe other end of the resistor R2 is connected with the first input end of an amplifier NIA, the second input end of the amplifier NIA is connected with one end of a resistor R2, and the other end of the resistor R2 is grounded; the output end of the amplifier NIA is connected with one end of a resistor R4, the other end of the resistor R4 is connected with the first input end of the amplifier NIB, the second input end of the amplifier NIB is connected with one end of a resistor R3, the output end of the amplifier NIB is also connected with one end of a resistor R3, and the other end of the resistor R3 is connected with the common end of the resistor R1 and the first input end of the amplifier NIA;
the positive electrode of the power supply VCC is connected with the first input end of the amplifier NIA, the negative electrode of the power supply VCC is connected with the second input end of the amplifier NIA, and the positive electrode and the negative electrode of the power supply VCC are grounded through capacitors;
one end of the resistor R5 is connected with the common end of the resistor R2 and the second input end of the amplifier NIA, and the other end is connected with the output end of the amplifier NIA and the common end of the resistor R4; the output end of the resistor R4 is used as an output standard current signal IT。
5. The standard current based DC undercurrent measurement system of claim 1, wherein the voltage signal V2Is less than or equal to the highest supply voltage of the voltage conversion circuit.
6. The standard current based small direct current measurement system according to claim 1, wherein the sampling resistor is a high precision, low temperature drift resistor.
7. A method for measuring a standard current-based dc small current, which is applied to a standard current-based dc small current measuring system according to any one of claims 1 to 6, the method comprising:
DC signal I to be measuredpA current transformer is connected into a square wave oscillator for modulation to obtain a modulation signal;
demodulating and amplifying the modulation signal by using an infinite gain filter and proportional amplification, and then sending the demodulation amplified modulation signal to a summation following output circuit to generate V1Simulating a voltage signal;
generating a reference voltage signal V using a digital processing circuitTConverted into standard current signal I by voltage conversion circuitTSent to a current transformer to be measured with a DC current signal IPPerforming superposition to superpose the standard current signal ITThe output waveform of the square wave oscillator is changed by the current transformer, so that the voltage signal output by the final summation follower is changed into V1T；
Using digital processing circuit to sum voltage signal V generated by following output circuit1/V1TCarrying out digital calculation processing, wherein the finally output signal can reflect the magnitude of the measured current signal;
meanwhile, a sampling resistor R is adopted to carry out comparison on a reference current signal ITSampling and converting into a voltage signal V2Returning to the digital processing circuit to output standard current signal ITAnd (6) judging the accuracy.
8. The method of claim 7, wherein the voltage signal V generated by the summing follower output circuit is processed by a digital processing circuit1/V1TCarrying out digital calculation processing, wherein the finally output signal can reflect the magnitude of the measured current signal; wherein:
V1＝IP*K*(1+ΔT)
V1T＝(IP+IT)*K*(1+ΔT)
in the formula, K is the integral gain of the proportional amplifying circuit, and delta T is the influence factors of environment, position and electromagnetic field;
the magnitude of the measured direct current is calculated by combining the two formulas, and the calculation formula of the measured current signal is as follows:
IP＝V1IT/(V1T-V1)
in the formula IPIs the measured current signal.
9. The method of claim 7, further comprising zero point calibration, wherein the method corrects the output zero point through the output of the digital processing circuit before the test, so that the final output signal accurately reflects the magnitude of the input dc current signal to be tested.
10. The method according to claim 7, wherein the sampling resistor is a high-precision low-temperature drift resistor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111369983.2A CN114062764A (en) | 2021-11-18 | 2021-11-18 | Direct current small current measuring system and method based on standard current |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111369983.2A CN114062764A (en) | 2021-11-18 | 2021-11-18 | Direct current small current measuring system and method based on standard current |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN114062764A true CN114062764A (en) | 2022-02-18 |
Family
ID=80277848
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111369983.2A Pending CN114062764A (en) | 2021-11-18 | 2021-11-18 | Direct current small current measuring system and method based on standard current |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114062764A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114994388A (en) * | 2022-05-25 | 2022-09-02 | 北京中联太信科技有限公司 | Method and system for magnetic superconducting micro-direct current detection and analysis |
-
2021
- 2021-11-18 CN CN202111369983.2A patent/CN114062764A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114994388A (en) * | 2022-05-25 | 2022-09-02 | 北京中联太信科技有限公司 | Method and system for magnetic superconducting micro-direct current detection and analysis |
| CN114994388B (en) * | 2022-05-25 | 2023-05-12 | 北京中联太信科技有限公司 | Method and system for detecting and analyzing magnetic superconducting micro direct current |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN107328980B (en) | Multi-core cable non-invasive current measuring method and measuring device | |
| CN108732404B (en) | Current sensor and multi-flux balance control circuit thereof | |
| CN110988430B (en) | Fluxgate heavy current sensor based on digital second harmonic detection and ripple compensation | |
| JP7070969B2 (en) | Crosstalk calibration for multi-channel systems | |
| JP2011528109A (en) | Input circuit for dielectric measurement of conductivity of fluid medium | |
| CN112362941B (en) | Annular current transformer and current measuring method thereof | |
| KR101952063B1 (en) | Leakage current detection device | |
| Entler et al. | Signal conditioning and processing for metallic Hall sensors | |
| CN114062764A (en) | Direct current small current measuring system and method based on standard current | |
| CN205826736U (en) | A kind of high accuracy single-turn cored structure formula electric current Online Transaction Processing | |
| GB2408808A (en) | Electric power meter with phase shift compensation | |
| CN113820645A (en) | Universal mutual inductor calibration equipment and mutual inductor calibration method | |
| CN116930589A (en) | AC/DC multi-air gap magnetic resistance current sensor and current measuring method | |
| CN109581265B (en) | Method for detecting direct current resistance of current transformer based on power error | |
| CN104897944A (en) | Method for measuring direct current greater than 50A | |
| CN114814330A (en) | Iron core-annular array multi-ring magnetic-sensitive current sensor and current measuring method | |
| CN103134981A (en) | Method for performing power detection, and associated apparatus | |
| CN116500533B (en) | Automatic error measurement method and system for current transformer | |
| JP3283986B2 (en) | Impedance measuring device | |
| Pascal et al. | Electronic front end for Rogowski coil current transducers with online accuracy self monitoring | |
| So et al. | A new current-comparator-based high-voltage low-power-factor wattmeter | |
| JP5877262B1 (en) | Calibrator for electromagnetic flowmeter | |
| CN114814512A (en) | Detection system for obtaining thyristor-level impedance of converter valve | |
| CN112904261B (en) | Harmonic calibration system and method, error harmonic component coefficient calculation system and method | |
| Houtzager et al. | Calibration systems for analogue non-conventional voltage and current transducers |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |