Background subtraction for coil voltages and currents

[samueljackson92]

The various coil currents and voltages on MAST are mostly not calibrated. For example for the following signals we can see that they are all shifted by a random background:

Annoyingly this offset is not consistent between shots:

We think that these could be calibrated on the fly by computing the offset and subtracting the background on a flat region of the full signal. For example in the following plot there is a flat region at either the beginning of the end of the signals.