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US 4,728,881 AGranted
Circuit for providing a controlled resistance
AssigneeHaven Automation Limited
InventorsWilliam A. Evans, Stuart L. Rowlands
Life of this patent
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AssigneeHaven Automation Limited
InventorsWilliam A. Evans, Stuart L. Rowlands
Estimating the term…
A circuit for providing a controlled resistance, the circuit comprising a pair of terminals for input of an excitation current, variable resistance means connected in the current path between the terminals, means for deriving a first signal representing the value of the voltage appearing across the terminals, means for deriving a second signal representing the value of the excitation current, means for generating a third signal representing a selected value of resistance to be provided between the pair of terminals, means for comparing the ratio of the first and second signals with the value of the third signal to derive a difference signal, and means for applying the difference signal to cause the variable resistance means to change in value such that said ratio tends towards exact equality with the selected value of resistance.
A circuit for providing a controlled resistance, the circuit comprising a pair of terminals for input of an excitation current, variable resistance means connected in the current path between the terminals, means for deriving a first signal representing the value of the voltage appearing across the terminals, means for deriving a second signal representing the value of the excitation current, means for generating a third signal representing a selected value of resistance to be provided between the pair of terminals, means for comparing the ratio of the first and second signals with the value of the third signal to derive a difference signal, and means for applying the difference signal to cause the variable resistance means to change in value such that said ratio tends towards exact equality with the selected value of resistance.
An apparatus for simulating the characteristic of a resistance-variable sensing element comprising a pair of terminals for the input of an excitation current, automatically variable resistance means connected in the current path between the terminals, means for deriving a first signal representing the value of the voltage appearing across the terminals, means for deriving a second signal representing the value of the excitation current, means for generating a third signal representing the value of resistance at a selected point on the characteristic to be simulated, means for comparing the ratio of the first and second signals with the value of the third signal to derive a difference signal, and means for applying the difference signal to cause the variable resistance means to change in value such that said ratio tends towards exact equality with the selected value of resistance.
Dependencies are inferred from the claim text.