Air Fuel Gauge calibration/ground ??? EXPERTS please

[jspaeth]

Hi, I am having some MINOR issues with datalogging and AFRs.

I am using an NGK AFR gauge and wideband.

It is 0-5V output, linearly from 9-16 AFR.

When driving, I see all ranges of numbers up to 16.00, and the calibration procedure has been recently performed (let sensor hang in clean air for 15 minutes and heat up, then there is a knob on the back that you turn until the display reads "CAL").

So, it appears the unit is calibrated.

ISSUE

The AFR unit has a signal output and signal ground, which I datalog via PFC Datalogit....

The signal ground always logs 0V.

The singal output wire logs close to the same as what I see, but seems to be SLIGHTLY lower.

I NEVER see any voltages on the sensor output above 4.8V, but it says that it should go up to 5V.


I am wondering if I have done something wrong, or if I should be entering ~4.8V as the upper limit in the Datalogit associated with 16.00.


As far as "overall" power and ground of the whole unit, I am pulling power from an ingnition source (12V) and the ground is on the intake manifold.

1) Can someone explain why it never outputs above 4.8V?
2) I technically use (signal volts-ground volts), but the ground reading is always 0V....

3) What should I do to make sure I am reading the correct AFR?

As of right now, it maxes out as far as my datalogging at 15.7, which should really be 16.00.....


Thanks


EDIT: Quoted from the manufacturer's installation instructions:


"When utilizing the analog output feature of the AFX, always be sure to connect the system ground (two BLACK wires) to the same location as the analog SIGNAL GROUND (BROWN wire). The analog output wires (YELLOW, BROWN) may be lengthened as long as the appropriate gauge wire is used and the connection is solid."


I don't get what this means....I have asked my dad, and he is an elec. engineer, and is also unsure why the signal ground coming out of the unit needs to be connected to a point that the other two ground are connected to.

Does this mean that I run the signal ground to my datalogit, and then splice a wire into this wire and run it to the ground point where the other two (black) wires were grounded?

[jspaeth]

UDPATE:

This morning, I rewired the grounds.

I wired the system ground and analog signal ground both to a good chassis ground point, and checked to make sure there was exactly 0 resistance along each path.

Finally, I added a third wire from that ground point and ran that to AN2 on the PFC dataloggit box.

RESULT:

NO CHANGE!

The AN2 log still shows exactly 0.000V, and when the car i just sitting there (hasn't been run in 16+ hours), AN1 NEVER reads above 4.82V.....

Something doesn't quite seem right.


The end result is that when my gauge says 16+, the data being logged only reads a max of 15.7.

This is worrisome, because all points that are TRULY above 15.7 will only log 15.7, causing the average to be skewed lower than it really is.....

Help!

[steve shadows]

I would get in touch with the manufacturer of your wideband system and they should be able to give you some support.

I had some cal issues with my LM1 when I bought it (because I bought one of the first 1000 units! haha that just came out) but they were extremely helpful in getting it all sussed out

[jspaeth]

I would get in touch with the manufacturer of your wideband system and they should be able to give you some support.

I had some cal issues with my LM1 when I bought it (because I bought one of the first 1000 units! haha that just came out) but they were extremely helpful in getting it all sussed out


Yeah I may try that....I was on Innovate's website reading some tech articles....that Klaus guy seems really badass as far as engineering goes...