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US 4,728,886 AGranted
Method and apparatus for converting an electrical signal into a proportional frequency
AssigneeLGZ Landis & Gyr Zug AG
InventorJan Petr
Life of this patent
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Abstract
A method and apparatus for converting an electrical signal into a proportional frequency is disclosed. Modulation of the output frequency resulting from polarity switching cycles having half-periods of unequal duration and capacitor voltages which might be non-zero at the time of polarity reversal are substantially avoided. This permits faster and more precise calibration.
Claims19
A method for converting an electrical signal into a proportional frequency comprising the steps of
- periodically switching said electrical signal with a first polarity reversing switch,
- adding a first reference signal to a signal proportional to said periodically switched electrical signal to form an addition signal,
- periodically switching said addition signal with a second polarity reversing switch which is switched synchronously with the first polarity reversing switch,
- successively charging and discharging an integrating capacitor by means of a current component proportional to said periodically switched addition signal and a selectively switched reference current, said reference current comprising a second reference signal whose value corresponds to twice the signal value of the first reference signal,
- comparing a voltage of the capacitor with a reference voltage to selectively switch said reference current, so as to enable production of a signal whose average frequency is proportional to the sum of said electrical signal and said first reference signal, and
- subtracting a frequency proportional to said first reference signal to produce a signal whose frequency is proportional to said electrical signal.
3 more elements
An apparatus for converting an electrical signal into a proportional frequency comprising,
- a first polarity reversing switch for periodically switching the polarity of said electrical signal,
- means for adding a first reference signal to a signal proportional to said periodically switched electrical signal to form an addition signal,
- a second polarity reversing switch which is switched synchronously with said first polarity reversing switch for periodically switching the polarity of said addition signal,
- an integrating capacitor which is successively charged and discharged by means of a current component proportional to said periodically switched addition signal and a selectively switched reference signal whose magnitude corresponds to twice the signal magnitude of said first reference signal,
- comparator means for comparing the capacitor voltage with a reference voltage to selectively switch said reference current, thereby enabling production of a signal whose average frequency is proportional to the sum of said electrical signal and said first reference signal, and
- means for subtracting a frequency proportional to the first reference signal to produce a signal whose frequency is proportional to said electrical signal.
3 more elements
Dependencies are inferred from the claim text.