ScoobyNet.com - Subaru Enthusiast Forum - Trying to connect a wideband 0-5v output to Motec Lamba Input

I have a wideband A/F ratio meter (similar to the MOTEC unit, although cheaper ;) ), it uses a NTK UEGO sensor (5 wire) and it also has a voltage output:

Voltage AFR
1.8 8.93
1.9 9.95
2.0 10.97
2.1 11.98
2.2 13.00
2.3 14.02
2.37 14.73 (stoich)
2.4 15.36
2.5 18.57
2.6 21.78
2.7 24.99

The wideband meter has an external voltage output, when I asked about the posibility of logging info with the MOTEC ECU the guy that sold me the wideband meter told me:

Quote:

"Yeah, you can connect this up. Pin 18 (Auxiliary Voltage Input on Motec) the Aux input looks like the right one to use. On J11 (voltage output of the wideband meter), there is a pad (see bottom of board) that is square, and one that is round. The round one is ground and the square one is signal. If you connect a wire from the square one to pin 18 you should get signal. To reduce noise you may want to connect the round one to the same ground as the Motec ground (battery -ve)."

But Pin 18 is Aux Voltage, so I asked if I could connect it to Pin 31 & 32 (La+ & La- on Motec ECU) and I got the following reply:

Quote:

"This hookup will probably work electrically, but our calibration for what the voltages correspond to may be different. I would leave the LA- off the round pin and just use battery ground for the LA-. Use the square pin to LA+."

There should be no problem regarding the calibration since the lambda sensor on a MOTEC ECU can be user defined ..... via A/D counts.

For example 2.37v = 14.73 (stoich) on the wideband meter.

Quote:

The table valus are A/D (Analog to Digital Converter) values at various Lambda values x 100 (therefore 100 = Lambda 1.00)

Therefore for 100 (or Lambda = 1) the A/D value is:

2.37 v x 1024 = 485.376 A/D counts
----
5.00 v

That way I can calculate most of the A/D values for the corresponding lambda values and on the view screen have an actual wideband lamdba reading .....

So will it work better connecting the external voltage output of the wideband meter to:

1) the Lambda input (pins 31 & 32 / La+ & La-) ?
2) the aux voltage input (pin 8) ?

And how should the signal and ground outputs of the wideband reader be connected ? should I connect the signal and ground or only the signal, afterall the wideband reader is connected to the car battery ..... or should I connect the ground to the battery -ve ?

Carlos Hiraoka