It’d be really nice to specify different scales for different lines.
For example, if I need to have pressure in kPa on the same chart as boiler temperature in C, the boiler temperature will be very compressed and not visually meaningful. If each of them has a separate scale, the relationships are much easier to see.
I’ve seen this implemented two ways, in order to isolate which scale is for which series:
1) One scale on either side of the graph. Series labels are at the right or left to indicate which scale they use.
2) One scale for each series, colour coded to match the series.