Power Issues = Compass Issues

In a previous post I complained about some compass issues that I have now attributed to, guess what, power!   Having sorted out my other power issues I came back to work on the compass a little and found that it was now reading accurately (e.g. agreed with a regular compass).    It still delivers the occasional errant reading when a train goes by but I have written some code to tune those out.   I now have a compass that is stable within what looks like about a degree.