Nick 2K2 SS

iTrader: (2)

Hey Guys,

Well I've done some reading and searched the forums on voltage offsets for the LC1 and I decided to do some testing myself. I'm looking for some help/Advise on how I should try and correct for my voltage offset. I've read soundengineers post on how to correct for an offset, but since my varies I wasn't sure how I should go about compensating for it.

First I recorded my voltage information by setting the LC1 to various “Flat Line” Voltages and then configured my EIO to show me the voltage reading by setting it to Volts / 1 + 0. Here is the data I got.

LC1 Voltage Output Set to 1.000 V
EIO Readings as Follows
.98145

LC1 Voltage Output Set to 2.000 V
EIO Readings as Follows
1.97754

LC1 Voltage Output Set to 3.000 V
EIO Readings As follows
2.97363

LC1 Voltage Output Set to 4.000 V
EIO Readings As Follows
3.93555

LC1 Voltage Output Set to 4.500 V
EIO Readings As Follows
4.35059

LC1 Voltage Output Set to 4.750 V
EIO Readings As Follows
4.52148

LC1 Voltage Output Set to 5.000 V
EIO Readings As Follows
4.65820

I’m trying to figure out how to correct for the voltage offset and it was doing pretty good until I was trying to read voltages greater then 4. According to the data, the higher the output voltage the more offset my voltage is. Should I try to use the lower 3 volt range and custom program my EIO so that the “useable voltage” and corresponding AFR range only uses the 0-3 volt range. I’m just not quite sure how I should adjust for my voltage offset. Any help or advise would be appreciated.

Thanks

Nick

jimmyblue

iTrader: (11)

It looks like there are both offset (ground?) and
gain errors that get worse with higher output
voltage.

These errors could come from the LC-1, the EIO
or the offset between the two. One thing that
would make it a little clearer is, a tiebreaker -
DMM readings across the EIO input under the
same conditions. The gain error is surprisingly bad.
Would like to see you slice the 3V-4V region a little
finer, how far out is it (say) 98% accurate would
be good to know.

I would also like to see the plain voltage difference
between the LC-1 ground and the EIO ground,
with the two otherwise not connected.

The look of this data says, you want to use the
0-3V range and set up the LC-1 to maximize the
"interesting" area and blow off outlying values
(like, do you care about anything over 15:1
or under 12:1? If no, then make 12:1=0.0V and
15:1=3.0V; now you have 100mV/point and the
25mV is "only" a 0.25 error term (and, depending
on how repeatable it turns out to be, perhaps
you just embed that in the transfer curve too;
12:1=0.02 and 15:1=3.03, like).

Nick 2K2 SS

iTrader: (2)

Thanks for the input. I did some more logging tonight and tried playing around with the offset in the EIO equation. I think I'm pretty close to the stoich reading be accurate but I'm going to do a little more testing. Unfortunately I don't have a DMM so I can't perform any of the tests you were asking for. All I can do is set the EIO to read the voltage out to me. Thanks for the input on the 0-3 volt range I will look into that more. Tonight I already set the EIO to to effectively use 0-3 volts for a 10-18 AFR range. It seems to do pretty good but I might refine it to a smaller AFR Range since I really don't care how much below 11 it is or how much above 16 it is. So I might try that tomorrow since I have the day off work!! Thanks again.

Nick