JPH09138245A - Measuring apparatus for quantity of electricity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a measuring apparatus by which the real-time property of an analytical operation and a computing operation is enhanced. SOLUTION: One pair of analog-to-digital converters 53 analog-to-digital- convert detection signals of a current sensor 1 and a voltage sensor 4. A processor 64 passes converted digital signals through a digital filter 55 so as to extract harmonics. In addition, the two digital signals are computed so as to compute a quantity of electricity. A communication interface 57 performs a communication between the processor 64 and a personal computer 3, and it sends data on the extracted harmonics and on the computed quantity of electricity to the personal computer 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric quantity measuring device for measuring electric quantities such as current, voltage and electric power.

[0002]

2. Description of the Related Art Currently, many current sensors and voltage sensors are small and inexpensive. With the spread of personal computers (personal computers), various attempts have been made to connect current sensors and voltage sensors to personal computers. In this way, the detection data of the current sensor and the voltage sensor can be easily managed on the personal computer. For example, it is possible to display the change over time in the current detected by the current sensor on the screen of the personal computer. Conventionally, as an electric quantity measuring device connected to a personal computer, for example, there has been a structure shown in FIG. In FIG. 3, reference numeral 1 denotes a portable current sensor that detects a current and outputs an analog detection signal. The current sensor 1 has a built-in CT (current transformer) to insulate signals. Reference numeral 2 is a measurement card that relays signals between the current sensor 1 and the personal computer 3. The measurement card 2 has a built-in analog / digital converter (A / D converter), and A / D-converts the analog detection signal of the current sensor 1 to pass it to the personal computer 3.

FIG. 4 is a block diagram showing the configuration of the apparatus shown in FIG. 4 that are the same as those in FIG. 3 are given the same reference numerals. FIG.
In the figure, 21 is an A / D converter for A / D converting the detection signal of the current sensor 1, 22 is a communication interface (communication I / D) for communicating with the personal computer 3 in accordance with a predetermined communication protocol.
F). The measurement card 2 forms a board, and an A / D converter 21 and a communication I / F 22 are formed on the board.

In the electric quantity measuring device shown in FIGS. 3 and 4,
Since the measurement card 2 only A / D-converts the detection signal of the current sensor 1 and passes it to the personal computer 3, only the measurement of the current cannot be performed for advanced analysis. For example, when it is desired to extract the harmonics contained in the alternating current, the detection signal of the current sensor 1 is sent to the personal computer 3, and then the personal computer 3 extracts the harmonics by FFT (Fast Fourier Transform) calculation. This allows
Since the harmonics cannot be extracted until the FFT calculation cycle comes, the real-time property of the analysis result deteriorates. This becomes a problem especially when the alternating current changes rapidly. Moreover, since only a current sensor is provided as a sensor, the power cannot be measured. Even if a voltage sensor is provided to measure the electric power, the measuring card 2 has only an A / D conversion function, and therefore the electric power cannot be measured until after the detection signal of the sensor is sent to the personal computer. by this,
The real-time property of the calculation result deteriorates.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and analyzes a signal waveform and measures an electric quantity on a measurement card which is a relay between a sensor and a personal computer. It is an object of the present invention to realize an electric quantity measuring device with improved real-time analysis and calculation by having a function to perform.

[0006]

The present invention provides a portable current sensor that detects a current and outputs an analog detection signal, and a portable voltage sensor that detects a voltage and outputs an analog detection signal. , A measurement card that is a board,
On the board, a pair of analog-digital converters for simultaneously analog-digital converting the detection signals of the current sensor and the voltage sensor, and a digital filter for the digital signals converted by the analog-digital converter. A processor that extracts harmonics by passing them, calculates a quantity of electricity by calculating a pair of digital signals converted by the analog-digital converter, and a communication interface that communicates between the processor and a personal computer. , Is formed, which is an electric quantity measuring device.

[0007]

In the present invention as described above, the pair of analog / digital converters simultaneously perform analog / digital conversion on the detection signals of the current sensor and the voltage sensor. The processor passes the converted digital signal through a digital filter to extract harmonics. In addition, the two digital signals are calculated to calculate the amount of electricity. The communication interface communicates between the processor and the personal computer, and sends the extracted harmonics and the calculated amount of electricity to the personal computer.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

1 is a block diagram showing an embodiment of the present invention. In FIG. 1, reference numeral 4 denotes a portable voltage sensor that detects a voltage and outputs an analog detection signal. Voltage sensor 4
Has a built-in PT (power transformer) to insulate signals. Reference numeral 5 is a measurement card that relays between the current sensor 1 and the voltage sensor 4 and the personal computer 3. The measurement card 2 uses the detection signals of the sensors 1 and 4 as A
In addition to an A / D converter for A / D conversion, a processor for analyzing and calculating a detection signal is also incorporated.

FIG. 2 is a block diagram showing the configuration of the apparatus shown in FIG. In FIG. 1, reference numerals 51 and 52 denote range switching circuits for current and voltage, which switch the detection signals of the current sensor 1 and the voltage sensor 4 to the level signals accepted by the measurement card 5. Input range can be switched on PC 3
It is performed by the signal from. If the sensor has a range switching circuit, the range switching circuits 51 and 52
May not be provided. 53 is a range switching circuit 51 and 5
It is a 2-channel A / D converter that A / D-converts the detection signals of the current sensor 1 and the voltage sensor 4 after passing through 2. 2
The detection signals of the current sensor 1 and the voltage sensor 4 are simultaneously sampled by the A / D converter 53 of the channel. 54
Is a processor that analyzes and calculates the detection signal (digital detection signal) converted by the A / D converter 53. The processor 54 is composed of a general-purpose microprocessor, DSP (digital signal processor), etc. according to the frequency of the detection signal. In the processor 54, 55 is a digital filter for extracting harmonics contained in the digital detection signal. By changing the pass band of the digital filter 55, harmonics of any order can be easily extracted. Reference numeral 56 is an arithmetic means for performing arithmetic processing on the digital detection signal to obtain an electric quantity. The calculating means 56 calculates electric power by multiplying two digital detection signals, for example. Computing means 5
In addition to electric power, 6 also obtains reactive power, power factor, phase difference between current and voltage, and the like. Further, with respect to the harmonics extracted by the digital filter 55, the harmonic distortion rate, the direction of the harmonics, etc. are also obtained. Such a processor 54 is described, for example, in the specification of Japanese Patent Application No. 4-67202 filed by the present applicant. 5
A communication I / F 7 performs communication between the processor 54 and the personal computer 3 according to a predetermined communication protocol. The A / D converter 53 and the processor 54 can be realized by a microprocessor with an A / D converter. The measurement card 5 forms a board, and the components 51 to 57 are formed on the board.

In the electric quantity measuring apparatus shown in FIGS. 1 and 2, when it is desired to extract harmonics and calculate electric power in real time, a digital filter 55 in the processor 54 is used.
The calculation means 56 performs extraction and calculation. The personal computer 3 displays the waveform of the extracted harmonic and the calculated value of the electric power in a graph. Understanding the harmonics of each order included in the detection signal, etc.
When detailed analysis is desired, the measurement card 5 performs A / D conversion of the detection signal and passes it to the personal computer 3 as in the conventional example. In this case, the real-time property is the same as that of the conventional example. This is because it is currently difficult to provide a low-cost microprocessor with an A / D converter with the function of FFT operation.

If only the harmonic analysis is performed and the power is not calculated, one of the current sensor and the voltage sensor may be omitted.

The input channel of the measurement card 5 may be other than two channels. For example, the number of input channels of the measurement card 5 is set to 6 and the A / D converter 53 has 6 input channels, so that power measurement of power lines of three-phase three-wire and three-phase four-wire becomes possible.

[0013]

According to the present invention, the processor is built in the measurement card that relays between the sensor and the personal computer, and the processor extracts the harmonics contained in the detection signal of the sensor by the digital filter and The electric quantity is obtained from the detection signal of. That is, before the detection signal is sent to the personal computer, the measurement card performs analysis and calculation. As a result, real-time analysis and calculation can be improved. Since the extraction of harmonics can be realized by a digital filter, it can be easily mounted on a measurement card.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of the device shown in FIG.

FIG. 3 is a diagram showing a configuration example of a conventional electric quantity measuring device.

FIG. 4 is a block diagram showing the configuration of the apparatus shown in FIG.

[Explanation of symbols]

 1 current sensor 3 personal computer 4 voltage sensor 5 measurement card 53 A / D converter 54 processor 55 digital filter 56 computing means 57 communication I / F

Claims (1)

[Claims] 1. A portable current sensor that detects a current and outputs an analog detection signal, a portable voltage sensor that detects a voltage and outputs an analog detection signal, and a measurement card that forms a board. On the board, a pair of analog-digital converters for simultaneously analog-digital converting the detection signals of the current sensor and the voltage sensor, and a digital signal converted by the analog-digital converter A processor that extracts a harmonic by passing through a filter and also calculates a quantity of electricity by calculating a pair of digital signals converted by the analog-digital converter, and a communication interface that communicates between the processor and a personal computer. An electrical quantity measuring device characterized in that a face is formed.