JPS641746B2 - - Google Patents

Description

[Detailed description of the invention] This invention switches and selects a plurality of alternating current electrical quantities,
This invention relates to a digital measuring device that uses one analog-to-digital converter.

For example, the method shown in FIG. 1 is used when measuring AC voltages and currents at multiple locations. In FIG. 1, the same number of transducers 2a...2n as the AC voltages and currents 1a...1n to be measured are provided to convert the measured quantities into DC voltage values, which are selected by the measurement selection circuit 4 and converted into analog-to-digital conversion. The amount to be measured is introduced into the device 8 in a time-division manner to digitize it, and then inputted into the data processing device 9 for data processing. In this conventional method, the response time is long because the transducer includes a rectifier circuit, a smoothing circuit, etc. in its internal circuit, and it is not possible to switch inputs at a high speed.
It was equipped with the same number of transducers as the locations to be measured, and measurements were made by selectively switching the DC output of the transducers. In this case, the transducers 2a...2n are generally expensive, so if there are many measurement points, the equipment cost increases.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inexpensive selective measuring device for a small current quantity of electricity without using an expensive transducer.

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3.

The selection measurement device of the present invention extracts the AC voltage or AC current to be measured through an isolation transformer and introduces it into the measurement selection circuit. The AC selected by the measurement selection circuit is supplied to the inputs of the 90 degree phase shift circuit and the sample and hold circuit. The 90 degree phase shift circuit shifts the phase of the selected alternating current by 90 degrees and supplies it to the input of the zero point detection circuit. The zero point detection circuit generates a zero point pulse at a point where the instantaneous value of the AC waveform is zero and supplies it to the sample and hold circuit. The sample and hold circuit uses the zero point pulse as a sampling pulse and samples and holds the AC input from the measurement selection circuit. The sample and hold voltage is an instantaneous value at 90 degrees from the AC zero point, that is, a DC voltage equal to the maximum value, so this is led to an analog-to-digital converter, and the digitized measured value is given as input to a computer for data processing. It is.

The details of the present invention will be explained with reference to FIG. 3 for the embodiment shown in FIG. In FIG. 2, the same parts as in FIG. 1 are indicated by the same symbols.

In Fig. 2, the amount of AC electricity to be measured 1a...1n
is extracted by the isolation transformers 3a...3n and guided to the measurement selection circuit 4. The measurement selection circuit 4 operates based on control input from a control circuit not shown in the figure, and selects one of the inputs from the isolation transformers 3a...3n and outputs it. This output is received by a 90 degree phase shift circuit 5 and phase shifted by 90 degrees, and further a pulse is generated at the zero point of the alternating current potential by a zero point detection circuit 6, and is inputted as a sampling pulse to a sample hold circuit 7. Since the input of the sample and hold circuit 7 is connected in parallel with the input side of the 90 degree phase shift circuit, a sampled and held voltage is produced at the output at the position where the instantaneous value of the AC to be measured is the maximum value. FIG. 3 shows the above-mentioned operating waveform diagram. Waveform A is the output A of the measurement selection circuit 4 of FIG. 2, and FIG. 3B is the output of the 90 degree phase shift circuit 5.
The output B of FIG. 3 is the output C of the zero point detection circuit 6,
FIG. 3D is a waveform diagram of the output D of the sample and hold circuit 7. As shown in the figure, the output of the sample and hold circuit stores the maximum value of the AC to be measured for half a cycle and sends it to the output as a constant DC value.

The above-mentioned DC output is an analog-to-digital converter 8.
The received data is digitized by the data processor 9, and then processed by the data processing device 9. Therefore, by simply using isolation transformers for a large number of electrical quantities to be measured, the measurement selection circuit 4 and below can use one set of devices in a time-sharing manner.

As is clear from the above explanation, the selection measurement device of the present invention does not use a conventional transducer,
It is led to the measurement selection circuit via a separate isolation transformer, samples and holds the maximum instantaneous value of AC, converts this DC value to an analog-to-digital converter, measures it as a digital value, and uses this as input data to the data processing device. Because the calculation process is performed as It also has the effect of improving.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional selective measuring device, FIG. 2 is a block diagram of an embodiment of the selective measuring device of the present invention, and FIG. 3 is an explanatory diagram of waveforms in the block diagram of FIG. 2. 1, 1a...1n...Amount of AC electricity to be measured, 2,
2a...2n...transducer, 3,3a
...3n...Isolation transformer, 4...Measurement selection circuit, 5...90 degree phase shift circuit, 6...Zero point detection circuit,
7...Sample hold circuit, 8...Analog-digital converter, 9...Data processing device.

Claims (1)

[Claims] 1 An isolation transformer provided for each of the plurality of AC quantities to be measured, a measurement selection circuit that selects any one output of the isolation transformer, and a measurement selection circuit that shifts the phase of the AC output of the measurement selection circuit by 90 degrees. a 90 degree phase shift circuit that causes the phase shift circuit to phase; a zero point detection circuit that generates a zero point pulse at the zero point of the AC output from the 90 degree phase shift circuit; and a zero point detection circuit that generates a zero point pulse at the zero point of the AC output from the measurement selection circuit; A selection measuring device comprising a sample-hold circuit that samples and holds a maximum value, and an analog-to-digital converter that converts the sample-and-hold voltage of the sample-and-hold circuit, which is an analog value, into a digital value.