there are o2 sensors

o2-a1
o2-a2
o2-a3


first sensor type is a two pin model. this outputs a uA current.
there is a 2nd type (same o2 sensor above) but three pins.


my guess is that 1 and 3 are power pins, 2 is signal



two pin model is replacable on dkey with sgx-40x
uA current is near identical

three pin model is replacable with ec410 though that is $30 more.

Save $30 by hacking the three pin board (which is near identical) to be
the two pin model. 

Making a foshw vers of these boards is trivial


There is a problem with electrochemical gas sensors. some of the main brands
(alphasense, and citicel) only supply to OEM. The OEM doesn't easily supply replacements (i.e. honeywell).
i will have to search some more.

in any case, this is left to the consumer to either gamble on a $150 seller in IL, or buy the $40 china option.
people will go to china every time.

because there is no official distributor that resells the products, consumers get shafted.
this is a shitty move by the companies. 

there are some options on dkey, but may not be 1:1 compatible (depends on the sensor).
more testing on output needed

why can't we just have official distributors instead of dealing with the OEM nonsense. mafia system. 