LC1 Voltage Offset / Correction
LC1 Voltage Offset / Correction 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
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
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).
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).
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
Nick
