"Battery" was more of an analogy than anything else. Its definitely not a thermocouple though. True, it has to be hot to operate, but the voltage isn't temperature dependent in any way as it is in a thermocouple. The voltage originates because of a chemical process catalyzed by platinum in the sensor, so I would still say that "battery" is a pretty good analogy.

The point is that its a high-impedance voltage source, and the only way to mess up its readings is to hang a meter with too low an input impedance on the output. Whether you think of it as a battery, fuel cell, generator, or voodoo is irrelevant as long as you remember that it is high impedance.

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Although an oxygen sensor is not a "storage" battery, I believe that they are considered a battery because it is a chemical reaction that creates the voltage. They actually have a solid electrolyte. A thermocouple, on the other hand, is based on the Seebeck effect which creates a voltage when two wires of the thermoelectric series of elements are connected together.
Bob D

Yep, O2 sensor is like a battery in that it generates a voltage, but very small current (high impedance as 440 said).

Practically speaking, you need to read it with a digital voltmeter (not an analog meter) since its impedance will be much higher than an analog meter.

Lou

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