Overlay maths based on channels not in both .ld

[zillarob]

What I am struggling with is overlaying maths that are based on channels that are not in both data files.

Say I want Trans output speed. One car has driveshaft speed, and the other has wheelspeed.
The first is easy, Trans output==driveshaft speed. Call it Trans_OP_DSS
The second would be Trans output==wheel speed*??Maths??*Rear Gear Ratio. Call it Trans_OP_Whl

The stuff I have setup now works fine individually, but one gets n/a when overlayed. It seems like the only channels available to overlay are the the ones in the first data file. Understandable, why would you want to overlay one cars driveshaft speed with another cars Wheel speed?

The problem is it seems to also not let you use those channels in maths that you may want to overlay, like Trans_OP_DSS and Trans_OP_Whl

I know I can change sensors around or build a driveshaft speed off of wheel speed, but any way to "unlock" the channels in the overlayed data file?

Also, any way to get 4 decimal places on the dash? I have some tables for calculating gears that can't be rounded to 3 places because they would overlap in the table.

[YuriK]

Hi zillarob,
Have you tried to use local math instead of global? If you haven't, try the following: add the expression "Trans_Speed = driveshaft_speed" for the log that has driveshaft_speed channel and create the expression "Trans_Speed = Wheel_Speed * Gear_Ratio" for the log file that has Wheel_Speed and Gear_Ratio channels. Then, when you overlay the data, you should be able to see Trans_Speed channel calculated for both data sets.

Regarding 4 decimal places in gear detection table, I don't think it will work well anyway. Difference of .000x volts is very small and I don't know if the sensor will be able to maintan that degree of accuracy when the vehicle is mooving, because of the vibration.

Regards!

[PQatPIT]

Thanks for tip using local maths!

But it is only local, ie. for one log file. For example if somebody has a huge log file collection then all of them must be "updated" with this local math. Wouldn't it be easier to apply global math (user-wise imo) and be done with it?

I mean, if somebody takes care of a few vehicles with M800 and other vehicles with M84 then there is a lot of housekeeping with log files. Of course there is possibility to change channel names in M800, but for log files already there it is quite a big hassle . Eh, am I missing something?

Thanks in advance!