Boots – shoes – and leggings
Patent
1994-11-04
1998-06-09
Voeltz, Emanuel Todd
Boots, shoes, and leggings
324141, 324142, G01R 21133, G01R 2106
Patent
active
057645230
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an electronic watt-hour meter for converting analog input signals of a voltage and a current into digital values and processing the digital values.
BACKGROUND ART
FIG. 34 shows a block diagram of a circuit for calculating an electric power of a conventional electronic watt-hour meter.
In FIG. 34, numeral 71 denotes a first successively comparing type A/D converter into which an analog current signal is input, numeral 72 denotes a second successively comparing type A/D converter into which an analog voltage signal is input and numeral 73 denotes a multiplier into which digital data corresponding to a voltage value and a current value from the respective successively comparing type A/D converters 71, 72 is input.
As shown in FIG. 34, the conventional electronic watt-hour meter includes the first and second successively comparing type A/D converters 71, 72 as means for converting analog quantities of a voltage and a current into digital values, and an electronic energy w is obtained by calculating these digital outputs by the multiplier 73.
In general, since the successively comparing type A/D converters 71, 72 quantize an analog input signal to a digital value in such a manner that an output is discretely increased with respect to the analog input signal by the same resolution, a successively comparing type A/D converter with high resolution is needed to obtain absolute precision for a low level input.
For example, when a current signal is supposed to be 1/120 of a maximum input, the following condition must be satisfied in order to keep the accuracy of a quantized current value to 0.5% or less. ##EQU1##
A successively comparing type A/D converter has a S/N ratio represented by converter when the sampling frequency is f.sub.2 =2.times.(signal frequency). Thus, a successively comparing type A/D converter having a resolution of m=15 bits is needed to keep the aforesaid precision of 0.5% or less.
On the other hand, as a method of improving the precision, there is a method of increasing a sampling frequency (f.sub.s) of a successively comparing type A/D converter, i.e., a so-called over-sampling method.
For example, when a sampling frequency (f.sub.s) is increased to a frequency which is 128 times a sampling frequency (f.sub.s =twice a signal frequency) determined by the Nyquist theorem, a quantized noise is dispersed to a wide bandwidth and the level of spectrum of each frequency component is lowered. When it is assumed here that a signal frequency=60 Hz and a sampling frequency (f.sub.s)=15.36 KHz, an over-sampling of 128 times is achieved and a noise level of the signal frequency component is improved by about 21 dB, which is equivalent to an improvement of a resolution of a successively comparing type A/D converter by 3-4 bits. In this case, a successively comparing type A/D converter having a resolution of 11-12 bits is needed to keep the precision of 0.5% or less of the quantized current value.
Therefore, a successively comparing type A/D converter having a high resolution and a multiplier to which many bits can be input are needed in conventional devices to obtain a high-precision electronic watt-hour meter, by which the circuit arrangement is of increased complexity and increased cost. In particular, this is very disadvantageous when electronic watt-hour meters composed of monolithic ICs are intended to be produced on a large scale.
SUMMARY OF THE INVENTION
An object of the present invention made to solve the above problems is to provide a high-precision electronic watt-hour meter having a simple circuit arrangement.
The electronic watt-hour meter according to a first aspect of the invention comprises first and second analog to digital conversion means for quantizing an AC current and an AC voltage, respectively, first and second moving average processing means for determining a moving average of each of the quantized AC current and the quantized AC voltage, first multiplication means for multiplying the AC current and the AC voltage each subjected
REFERENCES:
patent: 4459546 (1984-07-01), Arrington et al.
patent: 4564831 (1986-01-01), Wheable
patent: 4672555 (1987-06-01), Hart et al.
patent: 4752731 (1988-06-01), Toda
patent: 4878185 (1989-10-01), Brand et al.
patent: 4907165 (1990-03-01), Toda
patent: 4992725 (1991-02-01), Komatsu et al.
patent: 5068818 (1991-11-01), Uramoto et al.
patent: 5081413 (1992-01-01), Yamada et al.
patent: 5099195 (1992-03-01), Greer et al.
patent: 5134578 (1992-07-01), Garverick et al.
patent: 5151866 (1992-09-01), Glaser et al.
patent: 5170115 (1992-12-01), Kashiwabara et al.
patent: 5200750 (1993-04-01), Fushiki et al.
patent: 5305004 (1994-04-01), Fattaruso
patent: 5329282 (1994-07-01), Jackson
patent: 5363101 (1994-11-01), Veki
patent: 5396244 (1995-03-01), Engel
patent: 5440503 (1995-08-01), Maruyama
patent: 5448747 (1995-09-01), Garverick et al.
patent: 5461641 (1995-10-01), Abbiate et al.
patent: 5471209 (1995-11-01), Sutterlin et al.
S. Mazor, "Approaching Filters Discretely", Computer Design, vol. 21, No. 4, Apr. 1982 Winchester, Mass. pp. 159-162.
Takahashi Katuhiko
Tamai Shinzou
Yoshinaga Tooru
Cole Tony M.
Mitsubishi Denki & Kabushiki Kaisha
Todd Voeltz Emanuel
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