Measuring barometric pressure with a manifold pressure sensor in a microprocessor based engine control system

摘要

A method of measuring barometric pressure with a manifold pressure sensor (62) in a microprocessor based engine control system utilizes known engine operating conditions to interrogate the sensor. Also on engine turn-off, a power latch signal (158) is generated to delay power removal until the throttle valve (160) is driven open and the pressure sensor (62) is interrogated for its value. This value at this time is the ambient or barometric value of pressure. This value is stored in the microprocessor's (26, 28) memory (84, 86) and maintained by means of a standby voltage (80). During engine operation, the pressure sensor (62) is interrogated and value of the stored barometric pressure is changed by one unit of pressure if the stored and measured values are unequal.