Measuring method for frequencies of low-frequency signals

A frequency measurement, low frequency technology, applied in the field of frequency measurement, can solve problems such as weak anti-interference ability, inability to use civil single-phase AC frequency measurement, complex calculations, etc.

Inactive Publication Date: 2010-08-18
NANJING UNIV OF POSTS & TELECOMM
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Problems solved by technology

Although the measuring device has strong anti-interference ability, its disadvantage is that it needs a lot of complicated calculations when using the rotational vector angular velocity to convert the frequency, and the measuring device is dedicated to the frequency measurement of three-phase AC power, and cannot be used for the frequency measurement of civil single-phase AC power, let alone For frequency measurement of common non-three-phase low-frequency signals
[0004] Existing technology 2: Chinese patent application number 200510009292 discloses an AC frequency detection method, which is essentially a traditional zero-crossing detection method, but the anti-interference ability of this method is weak

Method used

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  • Measuring method for frequencies of low-frequency signals
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  • Measuring method for frequencies of low-frequency signals

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Embodiment Construction

[0038] The technical scheme of the present invention is described in detail below in conjunction with accompanying drawing:

[0039] The essence of the present invention is to fit a straight line by several sampling points, and the sampling points selected should not be too many. If there are more sampling points selected, the calculation will be complicated; If the number of sampling points is small, it is easily affected by interference. Therefore, users can select a reasonable combination and number of sampling points for calculation according to their needs.

[0040] In order to obtain more accurate measurement results, the suggested selection scheme of sampling points is: the number of positive sampling points is equal or approximately equal to the number of negative sampling points, and the number of sampling points can be determined according to the actual situation.

[0041] The principle of the present invention is illustrated by measuring the frequency of the two cy...

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Abstract

The invention provides a measuring method for frequencies of low-frequency signals. The method is characterized by comprising the following steps: sampling for tested electric signals; selecting a plurality of sampling points around the signal null point to fit a straight line which intersects with the time axis at the ZCP (zero crossing point) according to sampling values. The cycles or the frequencies of the tested signals can be calculated according to the ZCP. The method of the invention does not require the transformation of low-frequency signals into square waves, and is particularly suitable for the frequency measurement of low-frequency sinusoidal signals. The measuring system is easy to be tested and the cost of the equipment is low. The measuring system also boosts a good anti-interference capability and easy operation. The data obtained by this method is precise and reliable.

Description

technical field [0001] The invention relates to a frequency measurement technology for low-frequency signals, and the low-frequency signals include but not limited to civil alternating current. Background technique [0002] In daily life and production process, it is often necessary to monitor the frequency of the signal. The more accurate the measured frequency, the better the application effect. In the existing frequency measurement methods for low-frequency signals, the low-frequency signal is first formed into a square wave by a shaping circuit, and the time interval T between two adjacent rising or falling edges of the square wave is detected, and the frequency is obtained by calculating the reciprocal. In addition, there are some methods for measuring frequency by software, such as: zero-crossing method, analytical method, error minimization principle algorithm, DFT algorithm, quadrature demodulation method, etc. However, some of these algorithms are easy to implement...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R23/02
Inventor 戴尔晗赵元正孙海安林玲
Owner NANJING UNIV OF POSTS & TELECOMM
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