JP3314843B2 - AC measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC measuring apparatus for measuring an effective value, an average value rectified effective value calibration, a simple average value or an active power of an AC signal by digital operation.

[0002]

2. Description of the Related Art Effective value and average value rectification of AC signal RMS value calibration (performing full-wave rectification on an input signal to obtain its average value and multiplying it by π / 2 ^1/2 ), simple average value Alternatively, when the active power and the like are obtained by sum total averaging, an error occurs as shown by hatching in FIG. 4 unless the data acquisition period is an integral multiple of the AC signal. As a method for solving this problem, conventionally, the period of the AC signal to be measured is measured in advance, and data is captured for a period that is an integral multiple of the period. However, in this method, there is a problem that the period of data acquisition does not become an integral multiple of the period to be measured when the period changes because the period measurement and the data acquisition are not synchronized.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved AC measuring apparatus in which, when measuring an AC signal, the data acquisition period is always an integral multiple of the signal to be measured. It is what it was.

[0004]

According to the present invention, an AC signal to be measured is converted into a digital signal by an A / D converter, and the digital signal is added to an arithmetic circuit and arithmetically operated, and the arithmetic result is displayed on a display. In the above apparatus, a signal which becomes high level for a predetermined period is added to the D terminal, and the AC signal to be measured is shaped after being applied to the CK terminal, and the output is applied to the port of the arithmetic circuit. And the arithmetic circuit calculates the measured value of the measured AC signal while the output of the flip-flop is at a high level.

[0005]

According to the present invention, data is captured by a signal which is at a high level for a period which is an integral multiple of the period of the AC signal to be measured.

[0006]

Embodiments of the present invention will be described below in detail. FIG. 1 is a block diagram showing an example of a device on which the present invention is based. In the figure, 1 is a terminal to which an AC signal Vin to be measured is applied, 2 is an input circuit for converting Vin to a voltage of an appropriate value, and 3 is an A / D converter for converting the output of the input circuit 2 to a digital signal. Numeral 4 denotes an arithmetic circuit (digital signal processor) for calculating the effective value, average value rectification effective value calibration, simple average value, and the like of the measured signal Vi from the output of the A / D converter 3. 5 is a microprocessor, 6 is a display, and this display is a microprocessor 5
The output of the arithmetic circuit 4 is displayed under the control of.

Reference numeral 7 denotes a sampling clock generator for generating a sampling clock, 8 denotes a D-type flip-flop, and 9 denotes an AND gate. This gate receives the output of the sampling clock generator 7 and the output of the flip-flop 8, and the output is supplied to the A / D converter 3 as a sampling clock. Reference numeral 10 denotes a waveform shaping circuit for shaping the output of the input circuit 2, and the output is applied to the clock input terminal CK of the flip-flop 8. Reference numeral 11 denotes a temporary measurement period generator for outputting a high-level signal for a predetermined period, that is, a period extending over a plurality of cycles of the signal under test Vi. The output of this generator is applied to the D input terminal of the flip-flop 8. .

The operation of such a configuration device will be described with reference to the waveform diagram of FIG. FIG. 2A shows the measured AC signal Vin applied to the terminal 1. This signal Vin is converted into a voltage of an appropriate value by the input circuit 2 and then input to the A / D converter 3 and applied to the waveform shaping circuit 10 where the waveform is shaped as shown in FIG. You. The output of this waveform shaping circuit is applied to the CK terminal of the flip-flop 8.
On the other hand, the tentative measurement period generator 11 outputs a high level signal for a predetermined period as shown in FIG. A signal obtained by shaping the waveform of the input Vin to be measured is added to the CK terminal of the flip-flop 8. As a result, the rise of the waveform shaping signal, that is, (d) in FIG.
As shown in the figure, the Q output of the flip-flop 8 is at a high level for a period that is an integral multiple of the cycle of the signal under test Vin. This high level output opens the gate of the AND gate 9, during which the sampling clock from the sampling clock generator 7 shown in FIG. 2E passes through the gate. The clock that has passed through the AND gate 9 is shown in FIG.
(F). This clock is applied to the A / D converter 3 as a sampling signal, whereby the signal under test V
in is converted to a digital signal. The output of the A / D converter 3 is applied to an arithmetic circuit 4 to obtain the effective value of the signal under measurement Vin,
Average value rectification effective value calibration, simple average value, and the like are obtained by calculation, and the values are displayed on the display 6 under the control of the microprocessor 5.

In the device having such a configuration, the A / D
Since the sampling clock is always sent to the converter 3 only during a period that is an integral multiple of the cycle of the signal under test Vin, data is captured only during a period that is an integral multiple of the cycle of Vin.

FIG. 3 is a block diagram showing an embodiment of the apparatus of the present invention. In the apparatus shown in FIG. 1, the output of the sampling clock generator 7 is supplied to the A / D converter 3 via the AND gate 9, but in the apparatus of the present invention shown in FIG. Is directly supplied to the A / D converter 3 as a sampling signal. 1, the output of the flip flop 8 is used to open and close the gate of the AND gate 9.
In FIG. 3, the output of flip-flop 8 is applied to the input port of digital signal processor 4. The other parts in FIG. 3 are the same as those in FIG.
1 are given the same reference numerals as in FIG. 1 and their re-description is omitted.

In the apparatus of the present invention shown in FIG. 3, the A / D converter 3 always performs A / D conversion of the signal under test Vin based on the output of the sampling clock generator 7, and its output is an arithmetic circuit (digital signal). Processor 4). On the other hand, the Q output of the flip-flop 8 is applied to the input port of the arithmetic circuit 4, so that the arithmetic circuit 4 can read the state of the Q output of the flip-flop 8. When reading the output of the A / D converter 3, the arithmetic circuit 4 also reads the Q output of the flip-flop 8, and if the Q output is at the "high" level, calculates the measured value of the signal under test Vin. By using data,
Data is captured only during a period that is an integral multiple of the cycle of Vin.

[0012]

According to the present invention, by generating a signal which is at a high level for an integral multiple of the signal under test, the data acquisition period is always set to an integral multiple of the period of the signal under test. As a result, even when the effective value or the average value of the AC signal whose period is changed is obtained by the sum total averaging, there is an effect that a measuring device capable of obtaining the error with a small error can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a device on which the present invention is based.

FIG. 2 is a waveform chart for explaining the operation of the device of FIG.

FIG. 3 is a block diagram showing one embodiment of the present invention.

FIG. 4 is a diagram for explaining characteristics of a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input terminal 2 Input circuit 3 A / D converter 4 Arithmetic circuit 5 Microprocessor 6 Display 7 Sampling clock generator 8 Flip flop 9 AND gate 10 Waveform shaping circuit 11 Temporary measurement period generator

Claims (1)

(57) [Claims] An AC signal to be measured is converted into a digital signal by an A / D converter, and the digital signal is added to an arithmetic circuit and arithmetically operated.
In a device in which the calculation result is displayed on a display, a signal that goes high for a predetermined period is added to the D terminal, and the AC signal to be measured is added to the CK terminal after the waveform is shaped, and the output is applied. AC measurement, characterized in that a flip-flop to be applied to a port of the arithmetic circuit is provided, and the measured value of the AC signal to be measured is calculated by the arithmetic circuit while the output of the flip-flop is at a high level. apparatus.