CN208795797U - A kind of harmonic measuring device - Google Patents
A kind of harmonic measuring device Download PDFInfo
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- CN208795797U CN208795797U CN201821476780.7U CN201821476780U CN208795797U CN 208795797 U CN208795797 U CN 208795797U CN 201821476780 U CN201821476780 U CN 201821476780U CN 208795797 U CN208795797 U CN 208795797U
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- measuring device
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Abstract
The utility model discloses a kind of harmonic measuring devices, including sequentially connected current transformer, voltage conversion circuit, analog to digital conversion circuit, single-chip microcontroller and display screen.According to electromagnetic induction principle, end signal to be measured is acquired using current transformer, it is non-contacting between measurement end and end to be measured, realize non-intrusion measurement to measured signal, so as to avoid the influence of the electrical characteristic frequency spectrum to measured signal of measuring device, obtained measurement data is more accurate compared with the prior art.And carry out obtaining harmonic frequency by Digital Signal Analysis by selecting the single-chip microcontroller of different sample rates according to different frequency measurement ranges, further improve the accuracy of frequency measurement.Therefore harmonic measuring device disclosed by the utility model improves the accuracy of harmonic measure compared with the prior art.
Description
Technical field
The utility model relates to signal detection technique field, in particular to a kind of harmonic measuring device.
Background technique
A kind of important parameter of the frequency spectrum as signal plays an important role in signal analysis.For the frequency of electric signal
Spectrum harmonic measure is widely used in the analysis of the parameters such as signal distortion, frequency stability.
In the prior art, to the measurement of signal spectrum, the measuring devices such as oscillograph, spectrum analyzer are all that load is being believed
Number output end, and the electrical characteristic of measuring device to measured signal where circuit have it is certain influence, cause the change of circuit parameter
Change, and then causes measurement data inaccurate.
Therefore, how to improve the accuracy of harmonic measuring device measurement result is that those skilled in the art need to solve at present
The technical issues of.
Utility model content
The purpose of the utility model is to provide a kind of harmonic measuring devices, are improved compared with the prior art to harmonic measure
Accuracy.
In order to solve the above-mentioned technical problem, the utility model provides a kind of harmonic measuring device, comprising:
Current transformer, for obtaining measuring signal；
The voltage conversion circuit being connect with the current transformer and the analog-to-digital conversion being connect with the voltage conversion circuit
Circuit, for the measuring signal to be converted to digital signal；
The single-chip microcontroller being connect with analog-digital conversion circuit as described, for according to frequency measurement range, using it is preset with it is described
The digital signal is converted to harmonic frequency by the corresponding sample rate of frequency measurement range；
The display screen being connect with the single-chip microcontroller, for showing the harmonic frequency.
Optionally, the current transformer is specifically MH803CT current transformer.
Optionally, the voltage conversion circuit specifically includes OP07 chip.
Optionally, the voltage conversion circuit specifically includes voltage order one and follows circuit, input terminal and the voltage order one
What the level shift circuit and input terminal for following the output end of circuit to connect were connect with the output end of the level shift circuit
Secondary voltage follows circuit.
It optionally, further include the voltage-stabiliser tube that the output end of circuit is followed set on the secondary voltage.
Optionally, analog-digital conversion circuit as described specifically includes MAX197 chip.
Optionally, the single-chip microcontroller is specially MCS-51 single-chip microcontroller.
Optionally, the single-chip microcontroller is specially ARM Cortex-M kernel single-chip microcontroller.
It optionally, further include the LM7805 Voltage stabilizing module for being set to the power input of the single-chip microcontroller.
Optionally, the display screen is specially LCD display.
Harmonic measuring device provided by the utility model, including sequentially connected current transformer, voltage conversion circuit, mould
Number conversion circuit, single-chip microcontroller and display screen.According to electromagnetic induction principle, end signal to be measured is adopted using current transformer
Collection, be between measurement end and end to be measured it is non-contacting, non-intrusion measurement to measured signal is realized, so as to avoid measurement
The influence of the electrical characteristic of equipment frequency spectrum to measured signal, obtained measurement data are more accurate compared with the prior art.And lead to
It crosses and selects the single-chip microcontroller of different sample rates to carry out obtaining harmonic wave frequency by Digital Signal Analysis according to different frequency measurement ranges
Rate further improves the accuracy of frequency measurement.Therefore harmonic measuring device provided by the utility model is compared to existing skill
Art improves the accuracy of harmonic measure.
Detailed description of the invention
In order to illustrate more clearly of the utility model embodiment, letter will be done to attached drawing needed in the embodiment below
Single introduction, it should be apparent that, the drawings in the following description are merely some embodiments of the present invention, general for this field
For logical technical staff, without creative efforts, it can also be obtained according to these attached drawings other accompanying drawings.
Fig. 1 is a kind of structural schematic diagram of harmonic measuring device provided by the embodiment of the utility model；
Fig. 2 is a kind of schematic diagram of voltage conversion circuit provided by the embodiment of the utility model；
Fig. 3 is a kind of schematic diagram of analog to digital conversion circuit provided by the embodiment of the utility model；
Fig. 4 is the schematic diagram of a kind of single-chip microcontroller and display screen circuit provided by the embodiment of the utility model.
Specific embodiment
The core of the utility model is to provide a kind of harmonic measuring device, is improved compared with the prior art to harmonic measure
Accuracy.
The following will be combined with the drawings in the embodiments of the present invention, carries out the technical scheme in the embodiment of the utility model
It clearly and completely describes, it is clear that the described embodiments are only a part of the embodiments of the utility model, rather than all real
Apply example.Based on the embodiments of the present invention, those of ordinary skill in the art are under the premise of making the creative labor,
Every other embodiment obtained, belongs to scope of protection of the utility model.
Fig. 1 is a kind of structural schematic diagram of harmonic measuring device provided by the embodiment of the utility model.As shown in Fig. 1, this
Utility model embodiment provide harmonic measuring device include:
Current transformer 1, for obtaining measuring signal；
The voltage conversion circuit 2 being connect with current transformer 1 and the analog to digital conversion circuit 3 being connect with voltage conversion circuit,
For measuring signal to be converted to digital signal；
The single-chip microcontroller 4 being connect with analog to digital conversion circuit 3, for according to frequency measurement range, using preset and frequency from
The corresponding sample rate of measurement range converts digital signals into harmonic frequency；
The display screen 5 being connect with single-chip microcontroller 4, for showing harmonic frequency.
The measuring devices such as oscillograph in the prior art, spectrum analyzer are all that load is being believed in measuring signal frequency spectrum
Number output end, electrical characteristic to measured signal where circuit have it is certain influence, cause the variation of circuit parameter, and then cause
Measurement data inaccuracy.And harmonic measuring device provided by the embodiment of the utility model, measurement letter is obtained by current transformer 1
Number, be between measurement end and end to be measured it is non-contacting, non-intrusion measurement to measured signal is realized, so as to avoid measurement
The influence of the electrical characteristic of equipment frequency spectrum to measured signal, therefore obtained measurement data is more accurate compared with the prior art.
In specific implementation, the primary side of current transformer 1 is series at end to be measured, the secondary side of current transformer 1 is
Measurement end.According to electromagnetic induction principle, current transformer 1 is by the distortionless transmitting according to a certain percentage of the current signal at end to be measured
To measurement end.Current transformer transmits current signal according to following formula:
I1N1=I2N2 (1)
Wherein, I1It is end electric current to be measured, I2It is measurement end electric current, N1It is end-coil the number of turns to be measured, N2It is measurement end coil turn
Number.Resistance is accessed in measurement end, then ohmically voltage is directly proportional to the electric current at end to be measured, according to the ohmically electricity of measurement end
The current signal at end to be measured can be obtained in pressure signal.
Translation circuit corresponding with current transformer 1 uses transformer, and principle is that the primary impedance of transformer and secondary side hinder
The ratio between anti-square for being equal to the ratio between primary side the number of turns and secondary side the number of turns, it may be assumed that
Due to the impedance Z on measurement end (i.e. secondary side)2It is smaller, while turn ratio is also smaller, then it is (i.e. former to transform to end to be measured
Side) impedance Z1Can be smaller, the influence to primary circuit can be ignored substantially.
After the measurement end of current transformer 1, voltage conversion circuit 2, analog to digital conversion circuit 3, single-chip microcontroller 4 and display screen
5 are sequentially connected with.The measured signal at end to be measured is converted to measuring signal and exported in measurement end by current transformer 1, is become by voltage
Circuit 2 is changed by after measuring signal progress voltage transformation, is input in analog to digital conversion circuit 3 and voltage signal is converted into digital letter
Number, then be input in single-chip microcontroller 4.
Signal is transformed to frequency domain by time domain by FFT transform after sampling according to preset sample rate by single-chip microcontroller 4,
The maximum point of numerical value is found from frequency domain as fundamental frequency (i.e. fundamental frequency), is sampled according to the fundamental frequency size modification of this detection
Rate re-starts sampling and FFT transform, obtains a more accurate fundamental frequency and first harmonic magnitude.Since harmonic frequency is fundamental frequency
Integral multiple, local amplitude maximum point is found near the integral multiple of fundamental frequency, obtains corresponding harmonic frequency and its harmonic amplitude,
Obtain accurate harmonic frequency.
If single-chip microcontroller is with fsFor sample rate, by modulus conversion chip to N point of voltage signal acquisition of measurement end, so
The FFT transform for carrying out N point to it afterwards, obtains spectrum intervalsFrequency spectrum, at this
The corresponding frequency of the maximum numerical point of amplitude is found out on frequency spectrum as fundamental frequency.Meeting Nyquist (Nyquist)
Fundamental frequency is analyzed under the premise of sampling thheorem, if fundamental frequency is less thanIt then can be by reducing sample rate fsTo obtain more
Accurate measurement fundamental frequency.
After single-chip microcontroller 4 is converted to the final result of harmonic frequency, final harmonic frequency is shown in display screen 5.
Harmonic measuring device provided by the embodiment of the utility model, including sequentially connected current transformer, voltage transformation
Circuit, analog to digital conversion circuit, single-chip microcontroller and display screen.According to electromagnetic induction principle, using current transformer to end signal to be measured
Be acquired, be between measurement end and end to be measured it is non-contacting, non-intrusion measurement to measured signal is realized, to avoid
The influence of the electrical characteristic of measuring device frequency spectrum to measured signal, obtained measurement data are more quasi- compared with the prior art
Really.And by being selected the single-chip microcontroller of different sample rates obtained by Digital Signal Analysis according to different frequency measurement ranges
Harmonic frequency further improves the accuracy of frequency measurement.Therefore harmonic measuring device provided by the embodiment of the utility model
The accuracy of harmonic measure is improved compared with the prior art.
Fig. 2 is a kind of schematic diagram of voltage conversion circuit provided by the embodiment of the utility model.Fig. 3 is that the utility model is real
A kind of schematic diagram of analog to digital conversion circuit of example offer is provided.Fig. 4 is a kind of single-chip microcontroller provided by the embodiment of the utility model and shows
The schematic diagram of display screen circuit.
On the basis of the above embodiments, the utility model embodiment provides the specific type selecting of each section element.It needs
Illustrate, the type selecting in the utility model embodiment is not limited to for the type selecting of each section element, based on the above embodiment
Thought does adaptable adjustment to the type selecting of harmonic measuring device each section element, belongs to the protection scope of the utility model.
In specific implementation, current transformer 1 is specially MH803CT current transformer.MH803CT current transformer is
Specified input current is the accurate AC current transformer of 5A, and the turn ratio of this current transformer is 1000:1.
As shown in Fig. 2, specifically voltage conversion circuit 2 can be constructed based on OP07 chip.Further, voltage conversion circuit
2, which specifically include voltage order one, follows circuit, the level shift circuit that input terminal follows the output end of circuit to connect with voltage order one,
And the secondary voltage of the output end connection of input terminal and level shift circuit follows circuit.
The input off-set voltage and bias current of OP07 chip are smaller, and open-loop gain is bigger.Positive supply+Vs passes through
R1 and R2 partial pressure generates a bias voltage Vr in negative-phase input, and using amplifier void, short, resolution compares positive in output end
The direct current biasing of the more 2Vr of input terminal.
In order to realize impedance matching and improve load capacity, level shift circuit front stage devise a voltage with
With device, i.e. voltage order one follows circuit and secondary voltage to follow circuit.It, will by the voltage conversion circuit 2 based on OP07 chip
The voltage signal of input is transformed to the voltage signal of 0~5V, carries out analog-to-digital conversion to be sent into analog to digital conversion circuit 3.
Further, output voltage is excessive in order to prevent burns single-chip microcontroller, and harmonic measuring device can also include being set to two
Step voltage follows the voltage-stabiliser tube D of the output end of circuit, for controlling the size of output voltage.
As shown in figure 3, analog to digital conversion circuit 3 is specifically as follows the analog to digital conversion circuit based on MAX197 chip.MAX197
The output end of the level shift circuit of the analog input end and prime of chip is connected, the I/O port of data output end and single-chip microcontroller 4
It is connected.Chip select terminal CS, read strobe signal RD, write gate end WR are connected with single-chip I/O mouth respectively, controlled by single-chip microcontroller 4
System is communicated with MAX197 chip.
By realizing non-intrusion measurement and single-chip microcontroller 4 according to frequency measurement range, using default with current transformer 1
Sample rate corresponding with the frequency measurement range digital signal is converted into harmonic frequency, it is provided by the utility model
For the harmonic measuring device of harmonic measuring device compared to the prior art, high requirement is not necessarily to for the operational capability of single-chip microcontroller
Can be obtained more accurate measurement result, therefore the type selecting of single-chip microcontroller 4 is without excessive limitation, as single-chip microcontroller 4 can using cost compared with
Low MCS-51 single-chip microcontroller, as this system uses STC15W4K48S4.In order to further increase conversion accuracy, property can also be used
It can higher ARM Cortex-M kernel single-chip microcontroller.
Display screen 5 is specifically as follows LCD display, further, selects LCD12864 display screen in practical applications
(12864 be the dot matrix number of 128 × 64 lattice lcd modules).The connection of single-chip microcontroller 4 and display screen 5 is as shown in figure 4, LCD12864
The serial data R/W and serial synchronization clock E of display screen are connected with the I/O port of single-chip microcontroller 4, by single-chip microcontroller 4 control realize with
The communication of LCD12864 display screen, the parameters such as the peak-to-peak value of the current signal of reading and frequency are shown in LCD12864 display screen
On.
Previous measurement only uses single sample rate, and the measurement error that will result in certain frequency ranges in this way is larger.And
Circuit based on Fig. 2 into Fig. 4 under the premise of being 256 point FFT, is segmented frequency spectrum by the way of frequency spectrum refinement,
Every section of specific sample rate of setting, can make whole worst error less than 2% in this way.
Further, harmonic measuring device can also include the LM7805 pressure stabilizing mould of the power input set on single-chip microcontroller 4
Block.
Harmonic measuring device provided by the utility model is described in detail above.Each embodiment in specification
Be described in a progressive manner, each embodiment stress be with other embodiments do not have to place, each embodiment it
Between same and similar part may refer to each other.
It should be pointed out that for those skilled in the art, before not departing from the utility model principle
It puts, several improvements and modifications can be made to this utility model, these improvement and modification also fall into the utility model right
It is required that protection scope in.
It should also be noted that, in the present specification, such as first and second etc relational terms are used merely to one
A entity or operation are perhaps operated with another entity and are distinguished without necessarily requiring or implying these entities or behaviour
There are any actual relationship or orders between work.Moreover, the terms "include", "comprise" or its any variant are intended to
Cover non-exclusive inclusion, so that the process, method, article or equipment for including a series of element not only includes that
A little elements, but also other elements including being not explicitly listed either further include for this process, method, article or setting
Standby intrinsic element.In the absence of more restrictions, the element limited by sentence "including a ...", it is not excluded that
There is also other identical elements in the process, method, article or apparatus that includes the element.
Claims (10)
1. a kind of harmonic measuring device characterized by comprising
Current transformer, for obtaining measuring signal；
The voltage conversion circuit being connect with the current transformer and the analog to digital conversion circuit being connect with the voltage conversion circuit,
For the measuring signal to be converted to digital signal；
The single-chip microcontroller connecting with analog-digital conversion circuit as described is used for according to frequency measurement range, using the preset and frequency
The digital signal is converted to harmonic frequency by the corresponding sample rate of measurement range；
The display screen being connect with the single-chip microcontroller, for showing the harmonic frequency.
2. harmonic measuring device according to claim 1, which is characterized in that the current transformer is specifically MH803CT
Current transformer.
3. harmonic measuring device according to claim 1, which is characterized in that the voltage conversion circuit specifically includes OP07
Chip.
4. harmonic measuring device according to claim 3, which is characterized in that the voltage conversion circuit specifically includes level-one
Voltage follower circuit, the level shift circuit that input terminal follows the output end of circuit to connect with the voltage order one, and input
The secondary voltage connecting with the output end of the level shift circuit is held to follow circuit.
5. harmonic measuring device according to claim 4, which is characterized in that further include being set to the secondary voltage to follow electricity
The voltage-stabiliser tube of the output end on road.
6. harmonic measuring device according to claim 1, which is characterized in that analog-digital conversion circuit as described specifically includes
MAX197 chip.
7. harmonic measuring device according to claim 1, which is characterized in that the single-chip microcontroller is specially MCS-51 monolithic
Machine.
8. harmonic measuring device according to claim 1, which is characterized in that the single-chip microcontroller is specially ARM Cortex-M
Kernel single-chip microcontroller.
9. harmonic measuring device according to claim 1, which is characterized in that further include set on the single-chip microcontroller power supply it is defeated
Enter the LM7805 Voltage stabilizing module at end.
10. harmonic measuring device according to claim 1, which is characterized in that the display screen is specially LCD display.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201821476780.7U CN208795797U (en) | 2018-09-10 | 2018-09-10 | A kind of harmonic measuring device |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201821476780.7U CN208795797U (en) | 2018-09-10 | 2018-09-10 | A kind of harmonic measuring device |
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| CN208795797U true CN208795797U (en) | 2019-04-26 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110187176A (en) * | 2019-05-31 | 2019-08-30 | 中国电力科学研究院有限公司 | A kind of mains by harmonics measuring device and method |
-
2018
- 2018-09-10 CN CN201821476780.7U patent/CN208795797U/en active Active
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110187176A (en) * | 2019-05-31 | 2019-08-30 | 中国电力科学研究院有限公司 | A kind of mains by harmonics measuring device and method |
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