Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Plural ranges – scales or registration rates
Patent
1989-01-31
1991-02-19
Smith, Jerry
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Plural ranges, scales or registration rates
324126, G01R 1504, G01R 1506, G01R 1508
Patent
active
049947338
ABSTRACT:
A potentiometer used with a voltmeter has an impedance transformer to which a voltage to be measured is applied, a bank of resistors acting collectively as a variable resistor and having switches connected in parallel across the respective resistors of the bank, a switch control circuit, and a multiplier-setting circuit, all connected in series. The resistors have resistances r, 2r, 4r, 8r, . . . , 2.sup.n-1 r or 10.sup.0 (r, 2r, 4r, 8r), 10.sup.1 (r, 2r, 4r, 8r), . . . , 10.sup.n-1 (r, 2r, 4r, 8r), where r is a minimum, or unit, resistance value. The unit resistance value r multiplied by a multiplier N of two or more digits is equal to the resistance value of the variable resistor bank. This multiplier N expressed in decimal notation is set by means of a multiplier-setting circuit, which causes the switch control circuit to selectively open the switches, thereby adjusting the resistance value of the variable resistor bank according to the value of N so that the output voltage of the bank equals the full-scale voltage of the voltmeter, at which condition the value of N coincides with the magnitude of the voltage to be measured, provided the latter is not less than the full-scale voltage of the voltmeter, in which event an error indication is given.
REFERENCES:
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patent: 4000463 (1976-12-01), Katzmann et al.
patent: 4433287 (1984-02-01), Morita et al.
The Radio and Electronic Engineer, vol. 40, No. 1, Pearce et al.,; "Digital Carry Applied to Successive Approximation Digital Voltmeters", Jul. 1970, pp. 27-32.
IEEE Trans. on Instrum. and Meas., vol. IM-21, No. 4, Julie, "A High-Accuracy Digital Instrument Design for D.C. Measurements", Nov. 1972, pp. 323-8.
Electronic Technology, vol. 21, No. 1, Macalister et al., "A Transfer Standard Digital Voltmeters", Jan. 1978, pp. 3-8.
Baker Stephen M.
Daniel William J.
Riken Denshi Co. Ltd.
Smith Jerry
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