O2 Sensor Testing

[Mike Turner]

One of the engineers I work with used to work for Allied Signal, a company
that makes O2 sensors. He contacted them about how they test the sensors. I
was hoping for more specifics for the guys building EGOR but the answer
was.......

>>>>>>>>

The oxygen sensors are a Zirconia based "switching" sensor.  They basically
act as an on/off switch.  There are other "linear" sensors, but these are
not made by Allied Signal.

The sensors are tested using a natural gas fired burner.  The oxygen
content is regulated between a "rich" and a "lean" mixture.  The combustion
mixture flows at a rate of 1-3 meters per second past the sensor.  The
oxygen content is what causes the sensor to switch between off and on, but
the sensor only works when it has reached approximately 300 degrees
Centigrade.  (Hence the secondary function of the natural gas).

The natural "lean" indication is between 800 and 900 mV.

Another measure of the sensor is its "switching time".  This is the time
that it switches from "on" to "off".  For their measurements, AlliedSignal
measures the two points of 600 mV and 300 mV to assess this time.  My
contact person did not know exactly what times are considered good/bad, but
said that it was either in the low milliseconds or microseconds.

Looking at the wiring combinations, there are the following configurations:

1 wire - Unheated, wire is positive output, and metal casing is ground
connection
2 wire - Unheated, one wire is positive output, the other wire is the
ground connector
3 wire - Heated, two wires for heater, third wire for positive output,
metal casing is ground connection
4 wire - Heated, two wires for heater, other two wires are positive output
and ground connection

Apparently Bosch Automotive has a "Bosch Handbook" that goes into a good
explanation about the principles behind the oxygen sensor.
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