a/f ratio gauge...?
08-19-2009, 03:27 PM
#12
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
To expand on what "Bronto" said, a wideband sensor system consists of a sensor and a controller (a microprocessor) to operate read siganls from, and apply signals to, the sensor. This is because a wideband sensor consists of a narrowband sensor and an electrochemical O2 "pump" combined into a single unit.
A sample of exhaust gas enters a chamber in the sensor and the narrowband sensor tells the controller whether the sample is rich or lean. The then controller adjusts the voltage polarity and current flow to the O2 pump so as to pump oxygen into or out of the sample chamber until the sample is made to stochiometric (14.7:1 for gasoline), as reported by the narrowband sensor (actually it is when the NB sensor "switches" as Bronto described.
Because the wideband controller knows what polarity and how much current was required by the "pump" to make the sample stoichiometric it can reverse engineer the original AFR of the sample. This whole process can occur 6 to 30 times per second.
A sample of exhaust gas enters a chamber in the sensor and the narrowband sensor tells the controller whether the sample is rich or lean. The then controller adjusts the voltage polarity and current flow to the O2 pump so as to pump oxygen into or out of the sample chamber until the sample is made to stochiometric (14.7:1 for gasoline), as reported by the narrowband sensor (actually it is when the NB sensor "switches" as Bronto described.
Because the wideband controller knows what polarity and how much current was required by the "pump" to make the sample stoichiometric it can reverse engineer the original AFR of the sample. This whole process can occur 6 to 30 times per second.
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