CN110672916A - Open-type digital direct current measuring device - Google Patents
Open-type digital direct current measuring device Download PDFInfo
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- CN110672916A CN110672916A CN201911005411.9A CN201911005411A CN110672916A CN 110672916 A CN110672916 A CN 110672916A CN 201911005411 A CN201911005411 A CN 201911005411A CN 110672916 A CN110672916 A CN 110672916A
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- direct current
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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
-
- 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
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Measurement Of Current Or Voltage (AREA)
- Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)
Abstract
The invention discloses an open-type digital direct current measuring device, which comprises: the 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 quilt survey 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 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 quantity communication signal that accords with rated specification. The device can realize uninterrupted measurement of the direct current low current signal under the condition of ensuring that the performance is not reduced, and is convenient to install and maintain.
Description
Technical Field
The invention relates to the technical field of current detection, in particular to an open-type digital direct current measuring device.
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 the open-type digital direct current measuring device which can realize uninterrupted measurement of direct current signals (dozens of mA-hundreds of mA) under the condition of ensuring that the performance is not reduced and is convenient to install and maintain.
In order to achieve the above object, the present invention provides an open-type digital dc current measuring device, comprising:
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. Preferably, the square wave oscillator modulates an 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 the digital conversion circuit through the summing follower, and the amplified signal is converted into a digital communication signal capable of realizing RS485 communication through digital processing.
Preferably, the DC current of the measured DC current ranges from 50mA to 900 mA.
Preferably, 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.
Preferably, the magnetic core of the current transformer is manufactured by stamping, staggered, laminated and riveting.
Preferably, the magnetic core material of the current transformer is permalloy.
Preferably, the magnetic core of the current transformer is processed into a magnetic ring assembly through winding, and the exterior of the magnetic ring assembly is encapsulated by permalloy.
Preferably, the filter is an infinite gain filter, and is used for averaging signals and demodulating the detected direct current signal.
Preferably, 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 sizes meeting requirements are obtained later, and the zero point and the rated value of the device are calibrated.
Preferably, the summation follower is used for raising the analog signal amplified by demodulation 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 device can realize uninterrupted measurement of a signal with small direct current (dozens of mA-hundreds of mA) under the condition of ensuring that the performance of a product is not reduced, and the product is convenient to install and maintain. In addition, the sensor 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 diagram of an open-ended digital DC current measurement device according to the present application;
FIG. 2 is a schematic diagram of a power supply module of the present application;
FIG. 3 is a schematic diagram of a square wave oscillator, filter, scaling up, voltage conversion and summing follower circuit of the present application;
FIG. 4 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, the present application provides an on-state digital dc current measuring device, comprising:
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 1, 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. 1, 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. 2-4 are circuit diagrams for implementing the apparatus.
Wherein, this device is specifically as follows characteristics:
(1) the device has small volume and an open structure, and is convenient for on-site wiring and installation;
(2) the magnetic ring in the device adopts a customized structure, so that the magnetic performance is ensured not to be reduced;
(3) the device adopts a digital processing method and realizes the offset and sensitivity error compensation through software;
(4) the output of the device adopts RS485 output, and the interconnection and communication with an external system can be realized;
(5) the internal components and the output of the device adopt the modes of grounding, shielding and the like, thereby effectively reducing the interference of the ground and the surrounding magnetic field.
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. An open-ended digital dc current measuring device, said device comprising:
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.
2. The on-off digital DC current measuring device according to claim 1, wherein the square wave oscillator modulates the input DC current signal to be measured, the modulated signal is demodulated and amplified by the filter and the proportional amplifier, the amplified signal is transmitted to the digital conversion circuit by the summation follower, and the digital signal is converted into a digital communication signal capable of realizing RS485 communication by digital processing.
3. The open-type digital direct current measuring device according to claim 1, wherein the direct current of the measured direct current has a magnitude ranging from 50mA to 900 mA.
4. The on-off digital direct current measuring device according to claim 1, wherein the current transformer is an on-off current transformer, the on-off current transformer is used as an element having an energy storage delay function, and the measured direct current signal is modulated by a square wave oscillator, specifically: 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.
5. The open-type digital DC current measuring device according to claim 1, wherein the magnetic core of the current transformer is manufactured by stamping, cross-lamination and riveting.
6. The open-ended digital direct current measuring device according to claim 1, wherein the magnetic core material of the current transformer is permalloy.
7. The open-type digital direct current measuring device according to claim 1, 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.
8. The on-duty digital dc current measuring device according to claim 1, wherein the filter is an infinite gain filter for averaging signals and demodulating the measured dc current signal.
9. The on-off digital direct current measuring device according to claim 1, wherein the digital conversion circuit is configured to process the acquired analog signal, convert the processed analog signal into a digital signal suitable for RS485 communication, perform zero-point and rated value compensation on the analog signal output from the front end based on the zero-point and rated value compensation module, obtain a signal with a size meeting a requirement later, and calibrate the zero-point and rated value of the device.
10. The on-resistance digital DC current measuring device according to claim 1, wherein the summation follower is implemented to raise the demodulated and amplified analog signal by a certain amplitude for processing by the digital conversion circuit.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201911005411.9A CN110672916A (en) | 2019-10-22 | 2019-10-22 | Open-type digital direct current measuring device |
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| CN201911005411.9A CN110672916A (en) | 2019-10-22 | 2019-10-22 | Open-type digital direct current measuring device |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112260666A (en) * | 2020-10-10 | 2021-01-22 | 浙江巨磁智能技术有限公司 | Fluxgate circuit implementation method in low-frequency closed loop and high-frequency open loop |
| CN112763938A (en) * | 2020-12-24 | 2021-05-07 | 唐新颖 | Residual leakage detection method based on fluxgate |
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