>1: What sort of electrical load does the sensor want to have?
***************************************************
The sensor produces a voltage, typically 0 to a little over 1 volt D.C (see
below).
***************************************************
>2: How is the output voltage interpreted?
***************************************************
Well, that's the tricky part. Lambda sensors (oxygen sensors) are devices
that measure the oxygen content of the exhaust gas to determine the Lambda
ratio of carbon to oxygen. The output oscillates as a function of the
oxygen content inside the exhaust, relative to the outside air. For an
illustration (I don't have the figures handy so actual readings would be
different, but it will give you an idea of what's going on), using a second
as a time constant, at lean conditions it may cycle (voltage no voltage)
say once at about .1 volt. At full rich it may cycle say 10 times at 1.0
volts, and the values would be half that at stichometric (sp?). So it
isn't really a true voltage reading as such although the voltage does vary
as well but the computer (in fuel injection systems) takes the voltage, as
well as the time/cycles and correlates the data into a "reading" that
roughly translated into a fuel/air reading. Some systems use a reference
voltage of.45 volts. Since there is truly no such voltage as a constant
.45 v for an operating sensor, (or any "constant voltage, remember it is
constantly fluctuating) if the computer receives this voltage, it assumes
that the oxygen sensor is either not fully warmed up, or is not functioning
and uses .45 v as a reference and operates in a open loop mode (in effect,
bypassing the sensor)
Does that help or just make things more confusing?
Barry Schwartz (San Diego) bschwart@pacbell.net
|