Hi Felix,
I've put screenshots in the attached pdf file. You'll see pressure and temperature graphs with the standard index.php and with the autoscale function.
The pressure graph is useless without min/max scaling. The max y axis value is set correctly by Flot but the min y value is set to zero. As pressure variations are quite small compared to the absolute value, it's impossible to see anything more than a flat graph. I couldn't find any way to automatically set both ymin and ymax with Flot graph options. It's the reason why I added this piece of code. But may be there is a smarter way to do it.
Thanks,
Vincent