Importance

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Abstract

A cell/battery is excited by a time-varying signal that is characterized by periodically making step transitions between discrete levels. The immediate change in a responsive signal is determined by a circuit that is only enabled during a brief 'window' of time encompassing a step transition, and which employs a 'holding capacitor' to store dynamic conditions existing at the instant of enablement. Action of this 'holding capacitor' causes the circuit to only respond to changes in noise signals occurring during the enablement 'window' and not to the actual level of the noise itself. By making the 'window' sufficiently narrow, noise signals can change by only an acceptably small amount and can be removed by synchronously detecting the response to the step excitation and averaging the result over time. Two embodiments are disclosed. A first embodiment utilizes a step current-signal excitation and a voltage-signal response to directly determine a particular component of incremental resistance. A second, preferred, embodiment utilizes a step voltage-signal excitation and a current-signal response to directly determine a particular component of incremental conductance.

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First Claim