Abstract: In one embodiment, a circuit parameter of a sensor varies in accordance with an input useful in controlling an event associated with operation of an engine, for example, spark timing. The sensor is connected in an input sensing circuit characterized by a first order differential equation exhibiting an exponential transient whose time constant is representative of the circuit parameter, and hence of the input being sensed. A step function input is applied to the sensing circuit to cause the occurrence of an exponential transient, and concurrently a digital counter circuit begins counting clock pulses. The transient is compared against a predetermined reference, and when a predetermined relationship between the reference and the transient is attained, the counter circuit ceases counting pulses. The accumulated count is in the form of a binary word which may be used directly by a digital microprocessor in calculations for controlling the event.

Abstract: A fuel metering system controlling the mass fuel-air ratio in a spark ignition engine in response to fuel and air volume measurements. Linear responsive transducers respond to various temperatures, pressures, throttle positioning, fuel flow, air flow and engine operation for correcting the volume flow measurements of both fuel and air to mass flow measurements. A positive displacement, dual action pump delivers fuel to the throttle body of the engine in response to the mass of the air entering into the throttle body.