Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Nonlinear
Patent
1989-10-16
1990-09-25
Eisenzopf, Reinhard J.
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Nonlinear
324119, 324 99D, G01R 1510, G01R 1922
Patent
active
049596080
ABSTRACT:
Disclosed is apparatus and method for converting and displaying the total RMS and AC RMS values of a signal in a voltmeter. This conversion is accomplished in a system having a processor and a plurality of signal conversion stages. The first signal conversion stage comprises a low-pass filter to extract the DC component of the input signal followed by an analog-to-digital converter to convert the DC component into a digital value. The remaining signal conversion stages convert the AC component of the input signal to a series of smaller and smaller DC average values. Typically there are five of these AC conversion stages, each comprising a high-pass filter connected to a full-wave rectifier which is in turn connected to a low-pass filter followed by an analog-to-digital converter. The first AC stage high-pass filter is connected to the input signal and subsequent AC stage high-pass filters are connected to the output of the full-wave rectifier of the previous AC conversion stage. A processor inputs all the digital values from the various conversion stages, squares each of the values, and computes the sum of these squares. The processor then computes the square root of this sum to provide the RMS or AC RMS value. If the DC component digital value is used in the computation the result is the total RMS voltage of the input, but if the DC component is excluded, the result is the AC RMS value. The processor then displays either the total RMS or the AC RMS value on the display of the voltmeter.
REFERENCES:
patent: 3020479 (1962-02-01), Logan
patent: 3942095 (1976-03-01), Togreri et al.
patent: 4001697 (1977-01-01), Withers et al.
patent: 4599567 (1986-07-01), Goupillaud et al.
patent: 4786859 (1988-11-01), Arseneau et al.
Hayes; "Root Mean Square Digital Panel Meter . . . ", Analog Dialogue; Sep. 2, 1975; pp. 6-7.
Eisenzopf Reinhard J.
Hewlett--Packard Company
Nguyen Vinh P.
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