US3828255A
Expired / Lapsed
US
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Electric meter with logarithmically indicating digital reader
Assignee: Wandel and Golterman GmbH and Co
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Filing: 1972-08-07
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Granted: 1974-08-06
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Expires: 1992-08-07
Abstract
Abstract A variable voltage to be logarithmically indicated is fed to an input of an operational amplifier acting as a constant-current source in charging or discharging a capacitor at a constant rate determined by the magnitude of that voltage. The time required for the capacitor to charge or discharge from a reference potential to a potential equal or proportional to the variable voltage (or vice versa) is measured by a digital counter to which the output of a constant-frequency pulse generator is supplied, during the charging or discharging interval, through a binary frequency divider with a multiplicity of cascaded binary stages which are progressively cut in or out by a programmer responding to a predetermined number of pulses in the divider output, thereby modifying the pulse rate in the divider output in discrete steps by a factor of 2. Intermediate steps, designed to provide a closer approach to a logarithmic function, involve the alternate insertion of two final stages of stepdown ratio 5:1 and 7:1 in cascade with the binary stages to establish a pulse-rate modification by a factor of approximately square root 2.
Inventors
- 👤 E Schuon
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 15:15
CPC Classifications
G; G01; G01R; G01R19/00; G01R19/25; G01R19/255; G01R15/00; G01R15/08
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
298 words
A system for logarithmically indicating an analog value expressed by a variable voltage, comprising: a capAcitor; circuit means for reversibly charging said capacitor with constant current, said circuit means being provided with input means energizable to control the direction of current flow into said capacitor whereby the latter can be alternately charged and discharged at constant rates; a voltage comparator having a first input connected to said capacitor and provided with a second input for establishing a level of comparison with the charge of said capacitor; three terminals respectively carrying a first predetermined voltage, a second predetermined voltage and said variable voltage; switch means for connecting said input means to one of said terminals during a charging interval and to another of said terminals during a discharging interval, the remaining terminal being connected to said second input; timer means connected to said switch means and to said voltage comparator for establishing a measuring period between the beginning of said discharging interval and the arrival of the capacitor charge at said level of comparison, said measuring period having a duration proportional to the instantaneous magnitude of said variable voltage; a generator of pulses of constant cadence enabled by said timer means during said measuring period; counting means for said pulses connected to said generator; adjustable frequency-dividing means inserted between said generator and said counting means for stepping down said cadence to a variable pulse rate; and programming means responsive to a predetermined pulse count in the output of said frequency-dividing means for progressively modifying the step-down ratio thereof by a substantially constant factor of a1/n, n being a finite integer, in a number of steps sufficient to approximate a logarithmic relationship between the magnitude of said variable voltage and the total number of pulses counted during said measuring period.
Claim 2
Independent Claim
298 words
A system for logarithmically indicating an analog value expressed by a variable voltage, comprising: a capAcitor; circuit means for reversibly charging said capacitor with constant current, said circuit means being provided with input means energizable to control the direction of current flow into said capacitor whereby the latter can be alternately charged and discharged at constant rates; a voltage comparator having a first input connected to said capacitor and provided with a second input for establishing a level of comparison with the charge of said capacitor; three terminals respectively carrying a first predetermined voltage, a second predetermined voltage and said variable voltage; switch means for connecting said input means to one of said terminals during a charging interval and to another of said terminals during a discharging interval, the remaining terminal being connected to said second input; timer means connected to said switch means and to said voltage comparator for establishing a measuring period between the beginning of said discharging interval and the arrival of the capacitor charge at said level of comparison, said measuring period having a duration proportional to the instantaneous magnitude of said variable voltage; a generator of pulses of constant cadence enabled by said timer means during said measuring period; counting means for said pulses connected to said generator; adjustable frequency-dividing means inserted between said generator and said counting means for stepping down said cadence to a variable pulse rate; and programming means responsive to a predetermined pulse count in the output of said frequency-dividing means for progressively modifying the step-down ratio thereof by a substantially constant factor of a1/n, n being a finite integer, in a number of steps sufficient to approximate a logarithmic relationship between the magnitude of said variable voltage and the total number of pulses counted during said measuring period.
Claim 3
Dependent Claim
10 words
A system as defined in claim 1 wherein n 2.
Claim 4
Dependent Claim
33 words
A system as defined in claim 1 wherein said frequency-dividing means comprises a plurality of cascaded binary dividers and bypass switches controlled by said programming means for individually short-circuiting any of said dividers.
Claim 5
Dependent Claim
50 words
A system as defined in claim 3 wherein said frequency-dividing means further comprises two final dividers having step-down ratios of 5 : 1 and 7 : 1, respectively, said programming means alternately connecting said final dividers in cascade with said binary dividers between reversals of any of said bypass switches.
Claim 6
Dependent Claim
24 words
A system as defined in claim 1 wherein said circuit means comprises an operational amplifier having said capacitor connected in a feedback loop thereof.
Claim 7
Dependent Claim
37 words
A system as defined in claim 5 wherein said operational amplifier has a grounded noninverting input and an inverting input included in said feedback loop, said inverting input being connected through a resistor to said switch means.
Claim 8
Dependent Claim
27 words
A system as defined in claim 6, further comprising a grounded fourth terminal connectable to said inverting input by said switch means prior to said charging interval.
Claim 9
Dependent Claim
40 words
A system as defined in claim 7 wherein said one of said terminals carries a fixed voltage of one polarity, said other of said terminals carrying a fixed voltage of the opposite polarity, said remaining terminal carrying said variable voltage.
Claim 10
Dependent Claim
31 words
A system as defined in claim 7 wherein said one of said terminals carries said variable voltage, said other of said terminals carrying a fixed voltage, said remaining terminal being grounded.
Claim 11
Dependent Claim
22 words
A system as defined in claim 1 wherein said counting means comprises a digital counter presettable to a value other than zero.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-08-05 | 1978-02-04 | 1978-08-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-08-05 | 1982-02-04 | 1982-08-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-08-05 | 1986-02-04 | 1986-08-06 | $7700.00 | Window Closed / Lapsed |