Dash 3 Unreliable Lap/Sector Times

[DavidW]

Do you mean check the trace without the GPS inputs to just understand the effect of the accelerometers? I'll have a look tomorrow when I am back home to check exactly hwo much it drifts - normally though with GPS included it bounces around a lot when static, but I always assumed that was the GPS positional error - ie +- 3m or so

As far as longitudinal misalignment, I thought the Analysis software was able to adjust for small deviations thorugh one of the options - I guess the question is whether the DASH3 can do the same?

[924RACR]

Yes, the point being that if the car is level and static, the accelerometers should read no significant offset. It's just a check of sensor offset, not alignment.

[corey_dyck]

An easy accelerometer test:
Detach it from the car. Start logging. Set it on a flat surface on the front face, flat, and on it's side. Look at the data, plotted against time. You should see nice pure fore-aft and lateral G-forces with little to no blending. i.e. when you're at 1G towards the front face, you shouldn't see 0.2G to the side as well. If you do then something's wrong.

[DavidW]

I've tried the test suggested by corey_dyck and it is displaying approx +/- 1G in each direction on the DASH3 when I move the DL1 as suggested. There is however quite a lot of noise in the signal all the time to the order of +/- 0.02 G - is that what I would expect? I am also having problems getting the results to be repeatable from run to run, so I need to try some more tomorow. The Analysis software can give quite different results depending on what settings are selected for tuning the accelerometers. I need to play with the settings some more to work out what is best option.

[Turby]

+ or - 2% is not really an issue, you will probably have to filter the signal anyway to remove vehicle vibrations. Make sure the unit is mounted as level as possible. I tend to use the auto zero feature when loading runs which helps show the relative change in G.

[DavidW]

I've now fitted a new GPS Antenna on top of the roll bar, rewired the DL1 so it takes power feed from the main car supply at around 14V, and changed the mounting in the avoid any unwanted movement and still had problems at the last race at Snetterton.

In practice using a lap file with only one marker generated by the analysis software it did not record any laps at all. Replacing this by a file generated by the DL1 did improve matters to some degree and recorded 10 laps out of a 12 lap race, so better but not perfect. The key question is why it will not work on a lap file generated by the Analysis software? (I am using the excellent V8 beta software - I wonder if that is contributing to the problem?).

When looking at the data being recorded in Option 7.2 of the DASH3 menu it is not recording the Number of Satellites being tracked, and this field is not available for the Analysis software either - is this normal, or does it indicate something is not working properly?

I'm still trying to get some response from Kieran or Andy, but they seem to be igoring me - maybe they will read this....