Titania Oxide Sensor Resistance Characteristics

The titania sensor and ECU are wired as shown in the diagram. A one-volt potential is supplied at all times to the OX+ terminal of the sensor. The resistance value of the sensor changes abruptly as the stoichiometric boundary is crossed. The accompanying voltage and resistance graphs depict these characteristics and their influence on OX signal voltage.

The ECU comparator circuit is designed to monitor the voltage drop across R1. As the voltage drop across the sensor increases, the drop across R1 decreases and vice versa. This gives the OX signal voltage the same characteristic as the Zr02 sensor.

If sensor voltage drop is low, as it would be with a rich mixture, OX signal voltage will be above the comparator switch point, 450 millivolts, and the comparator output will be high. If the sensor voltage drop is high, OX signal voltage will be below the comparator switch point and the comparator output will be low.

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