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    Re: Titania oxygen sensors Archived Message

    Posted by Michael Whitworth on August 12, 2008, 12:14 am, in reply to "Re: Titania oxygen sensors"

    Hi Darren,

    >>>>Ed has the correct theory but the wrong around I think<<<<

    As many times as I read Ed appears to be saying the same as you.

    Since Tony brought up this subject I have searched high and low for a definitive answer to his question, namely does a titania sensor indicate high volts when rich or low volts when rich??

    It seems pretty conclusive that a lean mixture generates a high resistance but how does this equate to volts? How does the ecu interpret this resistance?

    I have two theories:

    1) The sensor element is supplied by a constant 5v the signal return goes back to ECU and through various circuitry finds its way to ground. The ECU monitors the return signal. My limited electronics knowledge tells me that the higher the resistance of the sensor element the harder it is for the 5v supply to get through to the signal return wire, therefore High resistance equals low volts which equal lean mixture. If the resistance is low it is easier for the 5v to get through therefore, low reistance equals high volts which equals rich mixture.

    2) The sensor is fed by the 5v supply and uses the earth of the heater circuit to complete a circuit to power up the sensor. The signal wire will be supplied with 5 volts from the ecu which is allowed to bleed through the resistive element of the sensor to earth similar to a coolant sensor. the higher the reistance (lean) the less voltage can escape to earth through the element leaving a high voltage on the signal wire. The lower the resistance (rich) the more voltage can escape through the element creating a low voltage reading on the signal wire.

    Both maybe totally wrong, they may not even make sense when I re read it myself in the cold light of day and of course I stand to be corrected in our search for the facts of this matter.

    And I find it astounding that all the literature about these sensors seem very contradictory and inconclusive.

    Mike

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