JPH0720182A - Method for measuring noise on low voltage cable way - Google Patents

Abstract

PURPOSE:To easily obtain a solution to low frequency noise by constituting an apparatus for accurately measuring a frequency and a level of noise in a low voltage cable way of private electricity receiving equipment. CONSTITUTION:A noise measuring apparatus 10 is placed on a low voltage cable way 3 of private electricity receiving equipment, wherein the noise measuring apparatus 10 is designed to sense a noise level against a frequency set in a fo-variable type bandpass filter 20 by using noise information on the cable way input via a signal preprocessing circuit 12 and a control signal from a control operation part 25. The control operation part 25 can not only sense a level of noise against one specified frequency but also can measure levels of noise against respective frequencies over a frequency band having a certain width to display them on a display and also can record the levels on a sheet with a recorder or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise measuring device for measuring the frequency component contained in the noise of a low piezoelectric path and its level in private electrical equipment and the like, and particularly to low frequency noise and its level (strength). ) Can be measured with respect to an arbitrary frequency.

[0002]

2. Description of the Related Art In private electrical equipment and the like, information obtained by an insulation monitoring device or the like is used as a carrier wave transmission line using a low-frequency transmission device using a low-frequency transmission device. A means for transmitting to the receiving device is used. However, when a signal is transmitted using the low piezoelectric path, if there is noise in the frequency band used for transmitting the signal, there is a problem that the signal cannot be transmitted in a good state. The problem of noise as described above has become a big problem particularly with the spread of home appliances and office equipment using semiconductor elements, and along with this, the voltage waveform distortion of the power system increases, and Has become an obstacle to the emergence. Therefore, in order to deal with the above-mentioned noise disturbance, it is necessary to identify the source of noise, grasp its frequency component, generation level, generation time zone, etc., and take countermeasures.

The noise disturbance of the low piezoelectric path as described above is
Mainly due to frequency components (low frequency) of several thousand Hz or less, but there is no model that can be used in the field as a noise measuring device dedicated to low frequency, and one with insufficient function and performance is used. There is a problem of having to do it. There are also noise measurement devices that are currently in practical use, such as FFT analyzers, spectrum analyzers, and selective level meters, for communication and wireless use. However, these devices are mainly used for high-frequency measurement. Therefore, there are many problems when used as a measuring device for low frequencies.

A: FFT analyzer ...
It is a device that measures the high frequency component of noise within a designated band by performing a fast Fourier transform on the waveform captured in the C memory. The above-mentioned device is for performing calculation from a stationary waveform stored in an IC memory to analyze a noise component,
Although suitable for performing various analyzes from one waveform, it is not possible to continuously record the state of noise. There is also a problem that it cannot be used as a device for selectively monitoring and recording the noise level of one frequency component. b: Spectrum analyzer: This device was originally developed for various measurements of electronic devices and wireless devices, and its purpose is to continuously observe the noise level in a specified band. Then, the device is an electronic device,
It is effectively used to measure the modulation characteristics, occupied band, sideband attenuation characteristics, etc. of wireless devices. c: Selective level meter: A device used for measuring the signal level of signal lines, etc., and extracts only the necessary frequency component (only one component) from a signal in which various frequency components of communication lines, electronic circuits, etc. are mixed. , Measure its level,
There is a function to record continuously. Therefore, there is a drawback that it is not possible to continuously observe the noise level in the designated frequency band as required for the noise measurement on the low piezoelectric path. Therefore, as shown in the above ac, when the noise measurement of the low piezoelectric path is performed by using the conventional measuring equipment, the resolution in the low frequency band is insufficient or the low frequency band measurement is not performed. There are many problems such as many unnecessary functions and complicated operations, and they are not suitable for measuring the low frequency band noise of the power system low piezoelectric path.

[0005]

SUMMARY OF THE INVENTION The present invention solves the problems of the conventional noise measuring device as described above. The frequency component and the level included in the noise of the low piezoelectric path are selectively or continuously within a certain frequency band. It is an object of the present invention to provide a noise measuring device configured so that the measurement result can be measured on a recording paper or a display while being measured.

[0006]

The present invention relates to a noise measuring device for measuring the frequency component contained in the noise of a low piezoelectric path and the magnitude of the frequency component. In the present invention, a signal processing circuit connected to the low piezoelectric path, a frequency variable bandpass filter, a control operation unit for outputting a control signal to the bandpass filter, and a frequency dividing circuit for frequency display are arranged. A noise measuring device, and a low frequency component obtained from the device,
A means for displaying the level is provided. Further, in the present invention, a means for setting a specific frequency to the noise measuring device and displaying a level of the specific frequency, and a frequency having a width to the noise measuring device are set and set. Means may be provided for displaying the level of the range of frequencies provided.

As described above, by constructing a mechanism for measuring the frequency component contained in the noise on the low piezoelectric path and the magnitude of the frequency component, the low frequency component and the noise level at that frequency Can be detected arbitrarily. Then, it is possible to easily take measures against noise of other devices connected to the low-voltage path, and it can be used as data for preventing the influence of noise on office equipment and the like.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A low-piezoelectric path noise measuring apparatus according to the present invention will be described with reference to the illustrated example. As shown in FIG. 1, the low-piezoelectric path noise measuring device of the present invention is a power receiving equipment for private use that feeds power from a high-voltage path 2 to a low-voltage path 3 via a transformer 1, a circuit breaker, a switch, and the like. The second type ground wire 5 is connected, and the noise measuring device 10 is further arranged,
The case where low frequency noise flowing in the low piezoelectric path 3 is measured is shown. In the noise measuring device 10 of the present invention shown in FIG. 1, between the input terminal 11 and the recorder output terminal 37, a signal preprocessing circuit 12, a pass center frequency “hereinafter referred to as fo” variable bandpass filter 20, The display and DC output circuit 35 is arranged, the noise signal of the low piezoelectric path is input through the input terminal 11, and the signal processed by the signal preprocessing circuit 12 and the signal of the control operation circuit 25 are input to the fo variable bandpass filter 20. The input is made to be able to measure the level of noise at a particular frequency. In the noise measuring device 10 of the present invention, when a signal in which various frequency components such as harmonics are mixed is input, the target frequency component is output by the fo variable bandpass filter 20 built in the device. And the output signal is
The voltage value is displayed on the display unit, and a DC voltage signal is output to a recorder or the like.

The device of the present invention is basically based on the measurement of the noise level between the low piezoelectric path and the ground, but the line current noise level can also be measured by providing a clamp CT or the like between the lines of the electric path. is there. Further, in the noise measuring device of the present invention, the control operation unit 25 can detect the noise level with respect to the frequency of a certain band. And in the noise measuring device,
It is possible to respectively display the noise level and frequency on a display unit such as a display, and further, by connecting to the recorder via the recorder output terminal 37,
It is also possible to continuously record the state of noise at continuous time.

The example shown in FIG. 2 shows the configuration of the circuit of the noise measuring device of the present invention, in which the device main body is connected to the low piezoelectric path of the private power receiving equipment through the input terminal 11 to measure the noise. To do so. Noise measuring device 10 of the present invention
In the configuration shown in FIG. 1, the signal preprocessing circuit 12 includes an input circuit 1
3, a gain adjusting circuit 14, a high pass filter 15 and an amplifier 16 are arranged. The signal preprocessing circuit 12
The input circuit 13 is configured as a means of low reactance and high impedance among the respective circuit members that make up the circuit, and the signal to be measured is input to the noise measuring device from the low piezoelectric path. In response to the,
The sensitivity is switched automatically or manually. The high-pass filter 15 is a high-pass filter that passes harmonic components, and is used in normal noise measurement.
When it is necessary to measure the power supply frequency component, the signal is passed through without using a high-pass filter. Further, the amplifier 16 is used to amplify the signal under measurement to a magnitude necessary for signal processing, and outputs the amplified signal toward the fo variable bandpass filter 20.

Fo connected to the signal preprocessing circuit 12
The variable band pass filter 20 is controlled to fo according to the control signal output from the control operation unit 25. A DC control voltage generator 26 and a voltage control frequency inverter 27 are arranged in the control operation unit 25, and the DC control voltage generator 26 is a DC voltage for controlling fo in the fo variable bandpass filter 20. For outputting the DC control voltage generator 2
In 6, using manual control or automatic control means,
As will be described later, the noise level in the set frequency band can be measured. Further, the voltage control frequency inverter 27 is a transmission circuit whose transmission frequency is controlled by the DC control voltage generator, and when the pass frequency of the band pass filter is fo, it matches the characteristics of the frequency control type fo variable band pass filter. Transmit frequency.
For example, if the transmission frequency is f, then f = fo × N,
The constant N is determined according to the characteristics of the fo variable bandpass filter.

Further, a frequency dividing circuit 30 is arranged between the control operation unit 25 and the display 31, and a voltage control frequency is applied by the frequency dividing circuit 30 in order to display the pass frequency fo of the bandpass filter on the display. Divides the output frequency of the inverter. For example, if the center frequency of the bandpass filter is fo, fo = f / N (f:
Voltage control frequency (inverter oscillation frequency), the processed information is transmitted to the display 31, and f
Display the frequency of the o component on the display. Further, a marker circuit 33 and a DC mixing amplifier 34 are provided between the control operation unit 25 and the DC output circuit 35.
And the marker circuit 33, as shown in FIG.
A signal for displaying the start f1 and the end f2 of the search frequency is output on the recording paper 40, and is displayed by momentarily setting the DC voltage to 0V. Also,
In the DC mixing amplifier 34, the progress of the marker circuit 33 and the DC output of the signal under measurement output from the rectifier circuit 21 are combined and output to the DC output circuit 35. The signal input to the DC output circuit 35 can be used not only as a signal for display on the display 36, but also can be output from the recorder output terminal 37 to the recorder and recorded on recording paper.

In the noise measuring apparatus of the present invention constructed as described above, the fo variable bandpass filter 20 is used.
With respect to the above, the target frequency component is output using the control information from the control operation unit 25 with respect to the noise information output from the signal preprocessing circuit 12. Fo of the present invention
In the variable bandpass filter 20, it is possible to perform manual control and automatic control by a control signal from the control operation unit 25. In the case of manual control, it is possible to take out a necessary frequency component from the signal under measurement in which various frequency components are mixed, measure its level, and continuously record it with a recorder. For example, as shown in the graph of FIG. 3, by operating the DC control voltage generating circuit 26, fo
By varying the pass center frequency of the tunable bandpass filter, the pass center frequency can be arbitrarily changed from the frequency shown by the solid line to the frequency shown by the chain line, etc. Level can be detected. Further, the frequency resolution is adjusted by changing the pass frequency bandwidth of the fo variable band pass filter.

On the other hand, when performing automatic control,
A signal for indicating the start f1 and the end f2 of the search frequency is output from the marker circuit 33 so that the noise can be displayed at the voltage level within the set frequency range. That is, as shown in the graph of FIG. 4, marks 41 and 42 indicating the beginning portion and the ending portion between f1 and f2 are displayed on the recording paper 40 by a signal from the marker circuit. However, the noise level can be continuously recorded in time series for each frequency component between the two set frequencies. The voltage-time control characteristic displayed on the recording paper is performed so that the frequency axis (horizontal axis) of the recorder is a linear scale or a logarithmic scale, and the set frequencies f1 and f2 can be freely changed. It is possible to set the search cycle (time) arbitrarily.

In the noise measuring apparatus of the present invention configured as described above, by using the fo variable bandpass filter capable of detecting the noise level within the designated frequency band, the device is connected to the recorder, By automatically controlling the DC control voltage generator, the frequency component contained in the noise and its magnitude can be continuously measured over a required time. In addition, in the present invention, the time of occurrence of noise, the level of occurrence of noise, and the frequency component can be easily measured, and a high-level analysis of the noise component flowing in the low piezoelectric path becomes possible. Then, in a device such as an insulation monitoring device that uses a low piezoelectric path as a carrier wave transmission path, the carrier wave transmission state can be continuously recorded. In the present invention, it is possible to measure the state of noise of a specified single frequency or the state of a carrier wave. That is, it is possible to extract an arbitrary frequency component from various frequency components of the low piezoelectric path, measure its level, and continuously record by a recorder. Furthermore, the device of the present invention is used for measuring noise of frequency components of several thousands Hz or less, is easy to operate, and can obtain a response time to a signal under measurement at high speed. Therefore, it can be easily applied as a device for measuring noise on a low-voltage path of a power system.

[0016]

The noise measuring device for a low piezoelectric path according to the present invention comprises:
Since it is configured as described above, by configuring the frequency component contained in the noise of the low piezoelectric path and the mechanism for measuring the magnitude of the frequency component, the low frequency frequency component and the frequency The noise level can be detected arbitrarily. Then, it is possible to easily take noise countermeasures for other devices connected to the low-voltage path, and it is possible that the influence of noise generated from office equipment or the like may interfere with the information transmission operation of other information transmission devices. It becomes possible to prevent. Further, in the noise measuring device of the present invention, the fo variable bandpass filter capable of detecting the noise level in the designated frequency band is used,
By connecting to the recorder and automatically controlling the DC control voltage generator, the frequency component contained in the noise and its magnitude can be continuously measured over a required time.
Therefore, by using the noise measuring device of the present invention, it is possible to accurately measure the noise on the low-voltage path of the power system, and measure the noise by specifying the noise source according to the noise information. Allows you to do it easily.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of an apparatus of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a noise measuring device of the present invention.

FIG. 3 is a graph showing characteristics of fo frequency by the fo variable bandpass filter of the present invention.

FIG. 4 is a graph showing an example of continuous measurement.

[Explanation of symbols]

1 transformer, 3 low piezoelectric path, 10 noise measuring device, 11 input terminal, 12 signal preprocessing circuit, 20 fo variable bandpass filter, 25
Control operation part, 26 DC control voltage generator, 31
・ 36 displays, 33 marker circuits, 3
5 DC output circuit, 37 recorder output terminal.

Claims (3)

[Claims] 1. A device for measuring a frequency component contained in noise on a low piezoelectric path and a magnitude of the frequency component, comprising a signal processing circuit connected to the low piezoelectric path, a variable frequency bandpass filter, and the bandpass. A control operation unit that outputs a control signal to the filter and a frequency dividing circuit for frequency display are arranged to configure a noise measuring device, and a means for displaying the low-frequency component and level obtained from the device. An apparatus for measuring noise on a low piezoelectric path, comprising: 2. The noise measuring apparatus for a low piezoelectric path according to claim 1, further comprising means for setting a specific frequency for the noise measuring apparatus and displaying the level of the specific frequency. 3. The noise of the low piezoelectric path according to claim 1, further comprising means for setting a frequency having a width to the noise measuring device and displaying a level in a range of the set frequency. measuring device.