JP2008028904A - Signal measuring instrument for power line communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a signal measuring device for power line communication which can be manufactured easily and inexpensively and which can measure not only a PLC signal communication state but also environmental noise at a measurement point.
A signal measuring device for power line communication 1 of the present invention includes a connection unit 7 for a power line 3 on which a PLC signal for power line communication is superimposed, and a frequency line of the power line communication supplied from the connection unit 7. A filter unit 8 for extracting the signal under measurement, a power measurement unit 9 for measuring the signal intensity of the signal under measurement extracted by the filter unit 8, and a measurement result obtained by the measurement unit 9 are displayed externally. And a display unit 10.
[Selection] Figure 1

Description

  The present invention relates to a signal measuring device for power line communication using a power line as a communication medium for information communication.

  A power line communication system (hereinafter referred to as a “PLC system”) is a high-frequency signal (as high as several kHz) that is used as a communication signal on a power line through which a commercial current (generally 50 Hz or 60 Hz) flows. The communication is performed by superimposing over several tens of MHz. Such a PLC system is a system capable of transmitting and receiving a large amount of data by using an existing power line (also called a distribution line or a light line) drawn into each house without using a dedicated communication line. Attention has been paid.

In the PLC system, a communication signal (hereinafter referred to as a PLC signal) is carried using a power line, so that a sufficient signal strength and low noise are required to ensure a good normal state.
However, various electrical devices such as household electrical appliances and network terminals are connected to the outlets in the home, and the PLC signal is easily affected by a decrease in impedance associated with the connection of these devices, and is also affected by environmental noise. Therefore, there is a drawback that transmission characteristics are easily deteriorated as compared with a data transmission cable such as a coaxial cable.

For this reason, when constructing a PLC system, it is necessary to measure whether or not the transmission characteristic at the connection point (signal injection point) between the PLC modem and the power line has reached a predetermined value.
By the way, a spectrum analyzer is generally used as a measuring instrument for measuring the signal strength of a high-frequency signal. However, this analyzer is very expensive and heavy, and requires an accessory such as a special filter or an adapter for coupling to the power line, so that there is a disadvantage that the measurement cost is increased. In addition, since advanced knowledge about various settings for the analyzer is required and skilled skills are required, this point is also a cause of high measurement costs.

Therefore, a PLC dedicated measuring instrument has been proposed that can easily find an optimal signal injection point without requiring special equipment or time and effort for the power line of the PLC system (see Patent Document 1).
This conventional measuring device includes a communication speed recognition means for identifying a communication speed at a signal injection point of a data communication signal performed via a power line, and a communication speed for displaying the communication speed recognized by the recognition means. Display means is provided, and the communication speed recognition means recognizes a speed at which communication is possible based on a comparison between a received signal level during non-communication and a received signal level during communication.
JP 2005-151465 A

  The above-mentioned conventional PLC dedicated measuring device recognizes the communicable speed based on the comparison between the received signal level at the time of non-communication and the received signal level at the time of communication. Therefore, a communication function equivalent to that of a PLC modem is required. Therefore, the conventional PLC dedicated measuring instrument is almost the same price as a normal PLC modem, and it is not as expensive as a spectrum analyzer, but has a drawback that it is still expensive as a measuring instrument alone.

  In addition, in the method of recognizing the speed at which communication is possible based on the comparison between the received signal level during non-communication and the received signal level during communication, it is possible to measure after the communication status with other base modems is established Therefore, measurement cannot be performed unless the other party's modem to be communicated is installed. For this reason, the communication status of compatible communication signals can be grasped, but the environmental noise at the measurement point cannot be measured accurately, and therefore the cause cannot be clearly identified when the transmission characteristics at a certain measurement point are poor. There is also a drawback.

  In view of such circumstances, the present invention is a signal measuring device for power line communication that can be manufactured simply and inexpensively and that can measure not only the communication status of PLC signals but also environmental noise at measurement points. The purpose is to provide.

In order to achieve the above object, the present invention takes the following technical means.
That is, the signal measuring device for power line communication of the present invention extracts a connection part to a power line on which a PLC signal for power line communication is superimposed, and a signal under measurement in the frequency band of power line communication supplied from this connection part. A filter unit that performs measurement, a power measurement unit that measures the signal intensity of the signal under measurement extracted by the filter unit, and a display unit that displays the measurement result obtained by the measurement unit to the outside. Features.

  According to the signal measuring instrument of the present invention described above, the signal under measurement within the frequency band of the power line communication supplied from the connection unit is extracted by the filter unit, and the signal strength of the extracted signal under measurement is measured by the power measurement unit. Since the measurement result is displayed on the outside by the display unit, the signal strength of the signal under measurement can be measured even if communication with the power line communication device such as the main unit modem is not established. Can be confirmed on the display.

For this reason, it is not necessary to provide a modem function for transmitting and receiving a PLC signal as a component of the signal measuring device, and the structure is simple and can be manufactured at low cost.
In addition, since the power measurement unit directly measures the signal strength of the signal under measurement within the frequency band of the power line communication extracted by the filter unit, the signal under measurement is transmitted from the power line communication device such as the master modem. Even in the case of environmental noise that is not a PLC signal, the signal strength can be measured.

The signal measuring instrument according to the present invention further includes intensity increasing / decreasing means for amplifying or reducing the signal under measurement so as to obtain a signal intensity suitable for the power range measurable by the power measuring unit and supplying the signal to the power measuring unit. It is preferable.
In this case, the signal to be measured is amplified by the intensity increasing / decreasing means so as to have a signal intensity suitable for the power range that can be measured by the power measuring unit, so even a signal with a relatively low intensity such as environmental noise can be measured. It can be measured appropriately. In addition, since the signal under test is reduced by the intensity increasing / decreasing means so that the signal intensity conforms to the power range that can be measured by the power measuring unit, even a signal with a relatively high intensity such as a PLC signal can be appropriately used. Can be measured.

Therefore, even in a situation where it is unclear whether the PLC signal is coming to the measurement fulcrum (contact point between the power line and the connecting portion), the signal strength of the signal under measurement at the measurement point can be easily measured. it can. In addition, since the power range of the signal under measurement that can be measured by the intensity increasing / decreasing means is substantially expanded, a relatively low-priced power measuring unit (power sensor) having a small power range can be used. The manufacturing cost of the measuring instrument can be reduced.
More specifically, the intensity increasing / decreasing means includes an amplifier circuit that amplifies the signal under measurement and supplies it to the power measurement unit, a reduction circuit that reduces the signal under measurement and supplies it to the power measurement unit, and a device under measurement The control unit can select an amplifier circuit when the signal strength of the signal is lower than the power range, and select a reduction circuit when the signal strength is higher than the power range.

Further, in the present invention, the filter unit is provided with a plurality of bandpass filters for extracting signals under measurement in different frequency bands that can be used for power line communication, and any of these filters is used as the power measurement unit. It is preferable to further provide switching means for selectively connecting.
In this case, since one of the plurality of bandpass filters having different frequency bands is selectively connected to the power measurement unit by the switching means, the signal strength of the signal under measurement is set for each of the plurality of frequency bands in which power line communication is performed. Can be measured.

  As described above, according to the present invention, a signal measuring device for power line communication that has a simple structure and is inexpensive can be obtained. Further, since not only the communication status of the PLC signal but also environmental noise at the measurement point can be measured, the cause of deterioration of the transmission characteristics at the measurement point can be more specifically identified.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a signal measuring instrument 1 for PLC according to the first embodiment of the present invention.
In the figure, an outlet 2 installed indoors is a part of the outlet of a power line 3 of a plurality of commercial power sources branched from a distribution board (not shown), and the power line 3 leading to the outlet 2 It communicates with a base unit modem (not shown) installed outdoors that can communicate with other networks. For this reason, the power line 3 has not only a function of conducting an alternating current serving as a commercial power supply but also a function as a signal transmission path for information communication.

As shown in FIG. 1, the signal measuring device 1 according to the present embodiment is attached to a housing 5 formed of a hollow box having a substantially rectangular parallelepiped shape and a wire cord 6 extending from the housing 5. In addition, a plug 7 is provided as a connecting portion connectable to the outlet 2 of the power line 3.
In the housing 5 of the signal measuring instrument 1, a filter unit 8 that extracts a signal under measurement in the frequency band of power line communication supplied via the plug 7 and the electric wire cord 6, and the filter unit 8 extracts the signal to be measured. Drives a power measurement unit 9 for measuring the signal intensity of the signal under measurement, a display unit 10 for displaying the measurement results obtained by the measurement unit 9 to the outside, the respective units 9 and 10 and a signal increase / decrease unit 13 described later. A control unit 11 for controlling is provided.

  Among these, the filter unit 8 has a low impedance for a signal under measurement including noise in a power line communication frequency band (several kHz to several tens of MHz: usually 2 MHz to 30 MHz), and the frequency of the commercial current (50 Hz). Or a filter circuit having a high impedance with respect to 60 Hz), and this filter circuit is constituted by, for example, an LC circuit in which connection portions of a plurality of coils connected in series to a pair of electric wires are connected in parallel with a capacitor. can do.

  The power measurement unit 9 is configured by a power sensor (power detection element) that detects the signal intensity of an electromagnetic wave (signal to be measured) in a frequency band used for power line communication that has passed through the filter unit 8. As this power sensor, a thermocouple detection sensor that detects the amount of heat generated in a resistor to which a signal to be measured is supplied by a thermocouple, or a diode detection sensor that applies the square detection characteristics of a diode element. Can be adopted.

  The display unit 10 of the present embodiment includes a plurality of LED elements 12 and displays the magnitude of the signal intensity according to the number of light emitted from the LED elements 12. Of course, as the display unit 10 for indicating the magnitude of the signal intensity, a liquid crystal display for displaying a numerical value of the signal intensity, or an analog display indicator for displaying the signal intensity by the rotation frequency of the display hand can be adopted. .

As shown in FIG. 1, an intensity increasing / decreasing unit 13 that amplifies or reduces a signal under measurement from the filter unit 8 and supplies it to the power measuring unit is provided in the housing 5 of the signal measuring instrument 1. The intensity increasing / decreasing unit 13 includes an amplifying circuit 14 that amplifies the signal under measurement and supplies it to the power measuring unit 9, and a reduction circuit 15 that reduces the signal under measurement and supplies it to the power measuring unit 9.
The control unit 11 includes a microprocessor connected to the power measuring unit 9, the display unit 10, the intensity increasing / decreasing unit 13 through an interface having an A / D conversion function, and each of the units 9, 10, and 13 is predetermined. The drive is controlled based on the processing program.

The control unit 11 determines whether or not the detection value (signal intensity of the signal under measurement) detected by the power measurement unit 9 is within the range of the power range of the power measurement unit 9, and the signal intensity is the power. If it is lower than the range, the amplifier circuit of the intensity increasing / decreasing unit 13 is selected. On the other hand, when the signal intensity is higher than the power range, the reduction circuit 15 of the intensity increasing / decreasing unit 13 is selected.
When the signal intensity of the signal under measurement is within the power range of the power measurement unit 9, the control unit 11 displays a display corresponding to the measurement value (for example, in the case of a plurality of LED elements 12). The display unit 10 is caused to perform lighting of a number proportional to the measured value).

As described above, in this embodiment, the signal intensity suitable for the power range measurable by the power measuring unit 9 is obtained by the amplification reducing unit 13 that amplifies or reduces the signal under measurement and the control unit 11 that controls the signal. In this way, intensity increasing / decreasing means for amplifying or reducing the signal under measurement and supplying it to the power measuring unit 9 is configured.
When the signal under measurement is amplified or reduced by the intensity increasing / decreasing unit 13, the control unit 11 calculates the measured value in consideration of the amplification factor or the reduction rate and displays the measured value on the display unit 10. .

  For example, in the case of the display unit 10 having a plurality of LED elements 12 shown in FIG. The signal intensity of the signal under measurement within the measurement range may be expressed by the number of other LED elements 12 emitted. Further, when a liquid crystal display or a display meter is employed as the display unit 10, the measured value calculated in consideration of the amplification factor or reduction rate in the intensity increasing / decreasing unit 13 may be displayed as a numerical value.

  According to the signal measuring instrument 1 of the present embodiment having the above configuration, when the plug 7 is inserted into the outlet 2, the signal under measurement in the frequency band of the power line communication supplied via the wire cord 6 is extracted by the filter unit 8. Then, the signal intensity of the extracted signal under measurement is measured by the power measurement unit 9 and the measurement result is displayed outside by the display unit 10. For this reason, the signal intensity of the signal under measurement can be measured even when communication with a power line communication device such as a master modem is not established, and the user can check the measurement result on the display unit 10.

Therefore, as shown in FIG. 1, a signal under test can be measured without providing a modem function for transmitting and receiving a PLC signal as a component of the signal measuring instrument 1, and the structure of the signal measuring instrument 1 is simplified. It can be manufactured at low cost. Further, since the signal strength of the signal under measurement in the frequency band of the power line communication extracted by the filter unit 8 is directly measured by the power measurement unit 9, the signal under measurement is a PLC signal from a power line communication device such as a master modem. Even if it is not environmental noise, the signal strength can be measured.
As described above, according to the signal measuring instrument 1 of the present embodiment, not only the communication state of the PLC signal but also environmental noise at the measurement point can be measured. It can be specifically identified.

FIG. 2 shows a signal measuring instrument 1 for PLC according to the second embodiment of the present invention.
The signal measuring device 1 (FIG. 2) of the present embodiment is different from the signal measuring device 1 (FIG. 1) of the first embodiment in that the signal under measurement in a different frequency band that the filter unit 8 can use for power line communication. Is provided with a plurality of band-pass filters 17 and a switching means 18 for selectively connecting any one of these filters 17 to the power measuring unit 9. In addition, since the other structure is the same as that of the case of 1st embodiment, the same code | symbol is attached | subjected to drawing in the same member, and detailed description is abbreviate | omitted.

As shown in FIG. 2, the switching means 18 is composed of a manual switching switch provided outside the housing 5, and a plurality of band-passes constituting the filter unit 8 when the user switches the switch. Any one of the filters 17 is selectively connected to the power measurement unit 9.
For this reason, in the signal measuring device 1 of this embodiment, the signal strength of the signal under measurement in which power line communication is performed can be easily measured for each of a plurality of frequency bands based on a user's artificial switch operation.

In addition, each said embodiment is an illustration and is not restrictive. The scope of the present invention is defined by the claims, and all modifications within the scope equivalent to the configurations described therein are also included in the scope of the present invention.
For example, instead of the plug 7 that can be connected to the outlet 2, a non-contact type coupler made of a coil or the like may be adopted as the connection portion for the power line 3. In this case, the signal strength of the signal under measurement can be measured even at a measurement point where the outlet 2 of the power line 3 is not provided.

  Further, in each of the above embodiments, the switching operation of the circuits 14 and 15 of the intensity increasing / decreasing unit 13 is automatically performed by the control unit 11, but the switching operation is performed by a switch manually operated by the user. May be.

It is a block diagram of the signal measuring device which concerns on 1st embodiment of this invention. It is a block diagram of the signal measuring device which concerns on 2nd embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Signal measuring device 2 Outlet 3 Power line 5 Case 6 Electric wire cord 7 Plug (connection part)
8 Filter unit 9 Power measurement unit 10 Display unit 11 Control unit (strength increasing / decreasing means)
12 LED element 13 Strength increase / decrease part (strength increase / decrease means)
14 Amplifying circuit 15 Reduction circuit 17 Band pass filter 18 Switching means

Claims (4)

A connection to a power line on which a PLC signal for power line communication is superimposed;
A filter unit for extracting a signal under measurement in the frequency band of the power line communication supplied from the connection unit;
A power measuring unit that measures the signal intensity of the signal under measurement extracted by the filter unit;
A display unit for displaying the measurement results obtained by the measurement unit to the outside;
A signal measuring instrument for power line communication, comprising:   2. The power line according to claim 1, further comprising an intensity increasing / decreasing unit that amplifies or reduces the signal under measurement so as to have a signal intensity suitable for a power range measurable by the power measuring unit and supplies the signal to the power measuring unit. Signal measuring instrument for communication. The intensity increasing / decreasing means includes
An amplifier circuit that amplifies the signal under measurement and supplies the amplified signal to the power measuring unit;
A reduction circuit for reducing the signal under measurement and supplying it to the power measurement unit;
A control unit that selects the amplification circuit when the signal strength of the signal under measurement is lower than the power range, and that selects the reduction circuit when the signal strength is higher than the power range; The signal measuring device for power line communication according to claim 2.   The filter unit includes a plurality of bandpass filters that extract the signal under measurement in different frequency bands that can be used for power line communication, and a switching unit that selectively connects one of these filters to the power measurement unit The signal measuring instrument for power line communication according to any one of claims 1 to 3, further comprising:

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