CN110672915A - Direct current measuring method based on open type structure - Google Patents
Direct current measuring method based on open type structure Download PDFInfo
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- CN110672915A CN110672915A CN201911005147.9A CN201911005147A CN110672915A CN 110672915 A CN110672915 A CN 110672915A CN 201911005147 A CN201911005147 A CN 201911005147A CN 110672915 A CN110672915 A CN 110672915A
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- direct current
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- method based
- current transformer
- square wave
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- 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
- G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
- G01R19/2506—Arrangements for conditioning or analysing measured signals, e.g. for indicating peak values ; Details concerning sampling, digitizing or waveform capturing
- G01R19/2509—Details concerning sampling, digitizing or waveform capturing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
- G01R1/02—General constructional details
- G01R1/18—Screening arrangements against electric or magnetic fields, e.g. against earth's field
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
- G01R1/30—Structural combination of electric measuring instruments with basic electronic circuits, e.g. with amplifier
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/20—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using galvano-magnetic devices, e.g. Hall-effect devices, i.e. measuring a magnetic field via the interaction between a current and a magnetic field, e.g. magneto resistive or Hall effect devices
Abstract
The invention discloses a direct current measuring method based on an open-type structure, which comprises the following steps: step 1: building a direct current measuring device; step 2: passing the direct current to be measured through the middle of a current transformer of the direct current measuring device; and step 3: turning on an auxiliary power supply of the device, measuring the measured current by using the turned-on direct current measuring device, and sending a test result in the direct current measuring device to an upper computer through 485; and 4, step 4: and the upper computer generates a measurement report based on the measurement result. The method can realize uninterrupted measurement of the direct current small current signal under the condition of ensuring that the performance is not reduced, and is easy to implement.
Description
Technical Field
The invention relates to the technical field of current detection, in particular to a direct current measuring method based on an open type structure.
Background
The invention is mainly based on direct current small current measurement, the measurement range is dozens of mA-hundreds of mA, the measurement aiming at the direct current signals is generally based on the magnetic modulation technology, and is mostly based on a closed loop structure, the installation and the maintenance are inconvenient, and the cost is high.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a direct current measuring method based on an open structure, which can realize uninterrupted measurement of direct current small current (dozens of mA-hundreds of mA) signals under the condition of ensuring that the performance is not reduced, and is easy to realize.
In order to achieve the above object, the present invention provides a dc current measuring method based on an open-type structure, the method comprising:
step 1: building a direct current measuring device;
step 2: passing the direct current to be measured through the middle of a current transformer of the direct current measuring device;
and step 3: turning on an auxiliary power supply of the device, measuring the measured current by using the turned-on direct current measuring device, and sending a test result in the direct current measuring device to an upper computer through 485;
and 4, step 4: and the upper computer generates a measurement report based on the measurement result.
Furthermore, the range of the direct current to be measured is 50 mA-900 mA.
Further, the dc current measuring device includes:
the device comprises a power supply module, a square wave oscillator, a current transformer, a filter, an amplifier, a voltage conversion module, a summation follower, a digital conversion circuit and a zero point and rated value compensation module; wherein, power module is used for supplying power to square wave oscillator and voltage conversion module, voltage conversion module is connected with the follower of summing, the direct current of surveying passes current transformer's magnetic core, current transformer's output is connected with square wave oscillator's input, square wave oscillator's output and current transformer's input and amplifier input are all connected, the output of amplifier is connected with the input of the follower of summing, the analog voltage signal of the follower output of summing directly sends into digital conversion circuit, realize zero point and rated value compensation through inside calibration software and handle, digital conversion circuit outputs the RS485 digital communication signal that accords with rated specification.
Further, the square wave oscillator modulates the input direct current signal to be detected, the modulated signal is demodulated through a filter, the filtered signal is amplified through an amplifier, the amplified signal is transmitted to a digital conversion circuit through a summation follower, and the amplified signal is converted into a digital communication signal capable of realizing RS485 communication through digital processing.
Further, current transformer is open-type current transformer, and open-type current transformer is used for as the component that has the energy storage time delay effect, and the direct current signal of being surveyed modulates through square wave oscillator, specifically embodies: when the detected direct current signal does not exist, the square wave oscillator outputs a standard square wave signal with the duty ratio of 1: 1; when a direct current signal to be measured with a certain amplitude exists, the output duty ratio of the square-wave oscillator changes, and a certain linear relation exists between the output duty ratio and the input signal.
Furthermore, the magnetic core of the current transformer is processed and manufactured in a stamping, staggered, laminated and riveting mode.
Further, the magnetic core material of the current transformer is permalloy.
Furthermore, a magnetic core of the current transformer is processed into a magnetic ring assembly through winding, and the exterior of the magnetic ring assembly is packaged by adopting permalloy.
Furthermore, the filter is an infinite gain filter and is used for solving the average value of the signal and demodulating the detected direct current signal; the digital conversion circuit is used for processing the acquired analog signals, converting the analog signals into digital signals suitable for RS485 communication, and performing zero point and rated value compensation on the analog signals output by the front end based on the zero point and rated value compensation module, so that signals with the size meeting the requirements are obtained later, and the zero point and the rated value of the device are calibrated.
Furthermore, the summation follower is used for raising the analog signal which is demodulated and amplified by a certain amplitude for processing by the digital conversion circuit.
One or more technical schemes provided by the invention at least have the following technical effects or advantages:
the method can realize uninterrupted measurement of the signal with small direct current (dozens of mA-hundreds of mA) under the condition of ensuring that the product performance is not reduced, and the product is convenient to install and maintain. In addition, the device in the method has an RS485 communication function and can return the acquired signals to the acquisition system in real time.
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 embodiments of the invention and together with the description serve to explain the principles of the invention;
FIG. 1 is a schematic flow chart of the DC current measurement method based on the open-type structure in the present application;
FIG. 2 is a schematic diagram of an open-ended digital DC current measurement device according to the present application;
FIG. 3 is a schematic circuit diagram of a power module of the present application;
FIG. 4 is a schematic diagram of a square wave oscillator, filter, scaling up, voltage conversion and summing follower circuit of the present application;
FIG. 5 is a diagram of a digital processing output and port protection circuit according to the present application.
Detailed Description
In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings. It should be noted that the embodiments and features of the embodiments of the present application may be combined with each other without conflicting with each other.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described and thus the scope of the present invention is not limited by the specific embodiments disclosed below.
Referring to fig. 1, an embodiment of the present application provides a method for measuring a direct current based on an open structure, including:
step 1: building a direct current measuring device;
step 2: passing the direct current to be measured through the middle of a current transformer of the direct current measuring device;
and step 3: turning on an auxiliary power supply of the device, measuring the measured current by using the turned-on direct current measuring device, and sending a test result in the direct current measuring device to an upper computer through 485;
and 4, step 4: and the upper computer generates a measurement report based on the measurement result.
Referring to fig. 2, an embodiment of the present application provides an on-type digital dc current measuring apparatus, including:
the device comprises a power supply module, a square wave oscillator, a current transformer, a filter, an amplifier, a voltage conversion module, a summation follower, a digital conversion circuit and a zero point and rated value compensation module; wherein, power module is used for supplying power to square wave oscillator and voltage conversion module, voltage conversion module is connected with the follower of summing, the direct current of surveying passes current transformer's magnetic core, current transformer's output is connected with square wave oscillator's input, square wave oscillator's output and current transformer's input and amplifier input are all connected, the output of amplifier is connected with the input of the follower of summing, the analog voltage signal of the follower output of summing directly sends into digital conversion circuit, realize zero point and rated value compensation through inside calibration software and handle, digital conversion circuit outputs the RS485 digital communication signal that accords with rated specification.
The detection principle is shown in figure 2, a power supply outside the sensor is converted into power supply +/-VR required by a square wave oscillator through proper processing, the input detected direct current signal is modulated through the square wave oscillator, the signal is demodulated and amplified through infinite gain filtering and amplification, and then the signal is converted into a digital communication signal capable of realizing RS485 communication through digital processing.
To be able to start oscillation, the oscillator circuit must satisfy two basic conditions of phase and amplitude. In addition, in terms of circuit structure, positive feedback and elements with energy storage delay function are required to exist, and meanwhile, in order to obtain stable oscillation amplitude finally, a negative feedback link cannot be completely absent, so that the oscillation amplitude is stable when positive and negative feedback is balanced. In fig. 2, the main function of the open-type current transformer is to provide an element with an energy storage delay function.
The measured direct current signal is modulated through a square wave oscillator, and the method is specifically embodied as follows: when the detected direct current signal does not exist, the square wave oscillator outputs a standard square wave signal with the duty ratio of 1: 1; when a direct current signal to be measured with a certain amplitude exists, the output duty ratio of the square-wave oscillator changes, and a certain linear relation exists between the output duty ratio and the input signal. The sensor realizes effective detection of the detected direct current signal based on the magnetic modulation principle. Specifically, the following description is provided: the size of the measured direct current signal is mainly related to the designed current transformer, and the detection precision is influenced when the measured direct current signal exceeds a certain measurement range. In addition, in order to ensure the modulation precision, the positive and negative power supplies are required to be stable and should not be too large.
The inductance L of the open-type current transformer serving as an energy storage element cannot be too small, because the smaller L is, the faster the current increasing or decreasing speed of the open-type current transformer is, the shorter the time from one turnover to the next turnover of the operational amplifier is, the shorter the oscillation period is, and once the time is shorter than the minimum response time of the operational amplifier, the operational amplifier loses response and does not turn over any more, so that the oscillation cannot be realized. On the other hand, the circuit needs to store energy by an inductor during oscillation, and the smaller the inductor, the less energy is stored, and less than a certain amount is not enough to start the circuit.
Magnetic core structure: the open-type current transformer is used as a signal modulation link, and key parameters of performance modulation performance are inductance L, saturation magnetic induction Br and the like. The inductor L is only dependent on the number of turns of a coil, the magnetic permeability of a magnetic core and the size, the structure and the shape of the coil, and the magnetic core is machined in a stamping, staggered, laminated and riveting mode in order to ensure that the open-type current transformer has the same performance parameters of a closed loop.
Selecting a magnetic core material: the magnetic properties are highly uniform and the permeability is high enough to be two of the most basic main requirements for the transformer core, and of course, in practical implementation, attention is paid to the effects of hysteresis and eddy currents, so that the core also has soft enough magnetic properties and high enough resistivity. In this case, a permalloy of a highly magnetic conductive material is selected in view of processing.
Shielding a magnetic ring assembly: the magnetic core is processed into a magnetic ring assembly through a certain required winding. Because the direct current signal to be measured is less, in order to reduce low-frequency magnetic field interference, the outside of the magnetic ring component is packaged by adopting permalloy, and the shielding layer mainly plays a role in shielding low-frequency size interference and positioning and fixing.
An infinite gain filter: the infinite gain filter has the main functions of solving the average value of signals and demodulating the direct current signals to be detected. Because the waveform output by the square wave oscillator cannot be absolutely symmetrical, the zero of the infinite gain filter cannot be completely zero. In order to ensure the demodulation precision, a digital conversion circuit at the rear end designs corresponding zero point compensation through software.
A digital conversion circuit: the digital conversion circuit is mainly used for processing the acquired analog signals and converting the analog signals into digital signals suitable for RS485 communication. In order to ensure the detection precision, software is adopted to carry out zero point and rated value compensation on the analog signal output by the front end, so that a signal with proper size is obtained later, and the zero point and the rated value of the sensor are calibrated. A summation follower: the summation follower is mainly used for raising the analog signal amplified by demodulation by a certain amplitude for processing by the digital conversion circuit.
Fig. 3-5 show circuit diagrams of specific implementations of the apparatus.
The method has the following characteristics:
1. the uninterrupted measurement of the direct current small current signal under small volume is realized by adopting an open type structure design method;
2. the magnetic performance of the magnetic ring assembly is not reduced by adopting a punching sheet staggered lamination riveting method;
3. the digital processing method is adopted, and the offset and sensitivity error compensation is realized through software;
4. and the interference of the ground and the surrounding magnetic field is effectively reduced by adopting a mode of shielding and grounding invalid signals.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. A direct current measurement method based on an open structure is characterized by comprising the following steps:
step 1: building a direct current measuring device;
step 2: passing the direct current to be measured through the middle of a current transformer of the direct current measuring device;
and step 3: turning on an auxiliary power supply of the device, measuring the measured current by using the turned-on direct current measuring device, and sending a test result in the direct current measuring device to an upper computer through 485;
and 4, step 4: and the upper computer generates a measurement report based on the measurement result.
2. The direct current measurement method based on the open structure according to claim 1, wherein the magnitude of the direct current to be measured is in a range of 50 mA-900 mA.
3. The direct current measurement method based on the open structure according to claim 1, wherein the direct current measurement device comprises:
the device comprises a power supply module, a square wave oscillator, a current transformer, a filter, an amplifier, a voltage conversion module, a summation follower, a digital conversion circuit and a zero point and rated value compensation module; wherein, power module is used for supplying power to square wave oscillator and voltage conversion module, voltage conversion module is connected with the follower of summing, the direct current of surveying passes current transformer's magnetic core, current transformer's output is connected with square wave oscillator's input, square wave oscillator's output and current transformer's input and amplifier input are all connected, the output of amplifier is connected with the input of the follower of summing, the analog voltage signal of the follower output of summing directly sends into digital conversion circuit, realize zero point and rated value compensation through inside calibration software and handle, digital conversion circuit outputs the RS485 digital communication signal that accords with rated specification.
4. The direct current measurement method based on the open-type structure, according to claim 3, characterized in that a square wave oscillator modulates an input direct current signal to be measured, the modulated signal is demodulated through a filter, the filtered signal is amplified through an amplifier, the amplified signal is transmitted to a digital conversion circuit through a summation follower, and the digital conversion circuit is digitally processed and converted into a digital communication signal capable of realizing RS485 communication.
5. The direct current measurement method based on the open structure according to claim 3, wherein the current transformer is an open current transformer, the open current transformer is used as an element with energy storage delay function, and the measured direct current signal is modulated by a square wave oscillator, which is specifically embodied as follows: when the detected direct current signal does not exist, the square wave oscillator outputs a standard square wave signal with the duty ratio of 1: 1; when a direct current signal to be measured with a certain amplitude exists, the output duty ratio of the square-wave oscillator changes, and a certain linear relation exists between the output duty ratio and the input signal.
6. The direct current measurement method based on the open structure according to claim 3, wherein the magnetic core of the current transformer is manufactured by stamping, cross-lamination and riveting.
7. The open-structure-based direct current measurement method according to claim 3, wherein the magnetic core material of the current transformer is permalloy.
8. The direct current measuring method based on the open structure according to claim 3, wherein the magnetic core of the current transformer is wound to form a magnetic ring assembly, and the magnetic ring assembly is externally encapsulated by permalloy.
9. The direct current measurement method based on the open structure as claimed in claim 3, wherein the filter is an infinite gain filter for averaging the signal and demodulating the measured direct current signal; the digital conversion circuit is used for processing the acquired analog signals, converting the analog signals into digital signals suitable for RS485 communication, and performing zero point and rated value compensation on the analog signals output by the front end based on the zero point and rated value compensation module, so that signals with the size meeting the requirements are obtained later, and the zero point and the rated value of the device are calibrated.
10. The direct current measurement method based on the open structure as claimed in claim 3, wherein the summation follower is implemented to raise the demodulated and amplified analog signal by a certain amplitude for the digital conversion circuit to process.
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| CN201911005147.9A CN110672915A (en) | 2019-10-22 | 2019-10-22 | Direct current measuring method based on open type structure |
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| CN109212304A (en) * | 2018-11-01 | 2019-01-15 | 东北电力大学 | The detection method of digital Weak current alternating current-direct current sensor based on direct current carrier communication technology |
| CN208833894U (en) * | 2018-04-27 | 2019-05-07 | 江苏诺森特电子科技有限公司 | A kind of automatic zero set calibration circuit of resistance welding current monitor |
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2019
- 2019-10-22 CN CN201911005147.9A patent/CN110672915A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN201397357Y (en) * | 2009-04-07 | 2010-02-03 | 绵阳市维博电子有限责任公司 | Wide-aperture direct current leakage current detection sensor |
| CN206684224U (en) * | 2017-04-10 | 2017-11-28 | 比亚迪股份有限公司 | Vehicle and the current sensor for vehicle |
| CN108387860A (en) * | 2018-04-03 | 2018-08-10 | 山东浩特电气有限公司 | A kind of electromagnetic current transducer and its error compensating method |
| CN208833894U (en) * | 2018-04-27 | 2019-05-07 | 江苏诺森特电子科技有限公司 | A kind of automatic zero set calibration circuit of resistance welding current monitor |
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Application publication date: 20200110 |