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SOME GOOD INFO ON TITANIA O2 SENSORS
Titania Oxygen Sensors
The remaining family of oxide ceramics found in “mother earth” are: magnesium oxide, aluminum titanate, zirconium oxide (ZrO2) and piezo ceramic. Aluminum titanate (derived from earth/dirt/soil known as rutile and anatase) (also known as Titanium dioxide, TiO2) was originally used in the production of exhaust gas oxygen sensors (EGO). This oxide does NOT have the ability to produce a self-voltage. Instead, in automotive oxygen sensor applications, a resistance is measured ranging from a low resistance of 1000 ohms (when the engine air/fuel mixture is too rich) to a high resistance of over 20,000 ohms (when the air/fuel mixture is considered too lean). This rapid change is read by the electronic control unit (ECU) or sometimes referred as the electronic control module (ECM) and that unit, in turn, generates its own voltage. This sometimes may confuse the automotive technician in thinking that the titania oxygen sensor “does generate a voltage” making it a zirconia oxygen sensor, when in reality the titania oxygen sensor truly CANNOT generate any voltage. The engine ECU supplies a base reference voltage of approximately one volt to the titania oxygen sensor. The ECU then reads the resulting voltage flowing through the sensor to monitor the air/fuel ratio. When the air/fuel mixture is rich, the resistance in the titania oxygen sensor drops at a fast rate and the sensor’s voltage signal (as generated by the ECU) is high. When the fuel mixture is lean, resistance in the titania oxygen sensor increases at a fast rate and the voltage signal read by the ECU drops drastically. This is when ‘cross counts’ become a major important factor in the effectiveness of any oxygen sensor. A good oxygen sensor should offer ‘cross counts’ of about one per second or in the case of NTK even more. Should the ‘cross counts’ be less than one per second; the titania oxygen senor most likely is getting sluggish and replacement is recommended. At this point, the person selecting the correct oxygen sensor replacement must be reminded that should a vehicle be using the circuitry in the ECU/ECM for a titania oxygen sensor, care must be taken that the other oxygen sensor, zirconia oxygen sensor, is NOT accidentally installed in the vehicle. Obviously, these two are definitely NOT interchangeable! Some vehicle manuals will make reference to a ‘voltage reading’ when dealing with the titania oxygen sensor. This voltage reading as discussed in this technical paper in detail does not necessarily mean that the vehicle has a zirconia oxygen sensor installed. In the heated version of the titania oxygen sensor, the heater resistance is 4 to 7 ohms.
The question has arisen as to “why do automotive manufacturers still install the titania oxygen sensors as OEM”? The best response that can be uncovered is that titania oxygen sensors do not depend upon outside air for reference when doing its job. Therefore, in vehicles that are regularly used in harsh environments and off-road circumstances, the reliability factor is more important than high technology. Zirconia oxygen sensors will not perform if the physical unit is covered in mud, dirt, grease, or oil blocking the ability of the sensor to compare outside air with the internal exhaust gases.
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