AEM 30-1931 Universal Fuel Ignition Controller 8 Channel - Manual (Page 30)

Page 30
Appendix
Oxygen Sensor theory.
Wide-band:
A wide-band sensor works by servo operation between a measuring cell (Nernst
cell) and an oxygen pumping cell. These two cells are contained in the O2 sensor where
the exhaust gas is sampled by a chamber connecting the two cells. The controller in the
car will change the current applied to the pump cell in an attempt to keep the Nernst cell
voltage at a predetermined level. The current that is needed to maintain this balance is
the indication of AFR that the ECU uses.
When the FIC is used to modify the signal from a wideband sensor the connection is
made to the Nernst cell. Because the Nernst cell acts like a variable voltage source with
a predictable impedance the FIC can modify the current from the Nernst cell to effect a
change to the AFR.
Narrow-band 0-1vdc Nernst type:
A narrow-band Nernst sensor produces a voltage that represents partial pressure of
oxygen left in the exhaust after combustion. This voltage will switch very rapidly as the
AFR moves in ether direction off of stoich (about 14.7:1). The cars controller manages
this by dithering about stoich. The FIC can override this signal with a programmable
square-wave to keep the car ECU from seeing other changes that are being made to
the fuel injectors or MAF.
F/IC Specs
Processor: Dual 16bit 32mips processors.
Logger:
Internal: 2 MB, 10ms max sample rate,
PC: 10ms fixed sample rate.
Pressure: 2psia - 40psia +/-.5psia resolution .1psia
Analog/MAF: 0vdc - 6vdc Input, 0vdc
– 6vdc Output, overload protected
Power: 8-15vdc
Switch Input: GND to activate
SW12: High-side driver, 1 amp max, overload protected
Injectors (8): 1.7 amps max, overload protected
O2 : 0vdc -3.5vdc,
Size: 4.2"L x 7.4"W x 1"H