Re: Plasma Voltage Servo

WRT plasma arc voltage vs torch to work distance:

Once I read an Amercan Welding Society paper on this subject.
According to this article, the arc voltage wavform is something of a
sawtooth. At the beginning of the cycle the arch starts at the top
of the material at a certain voltage. As it rapidly burns its way
down the face of the cut, the voltage ramps up to some peak at the
bottom surface of the material. At this point, the arc jumps back to
the top surface and the cycle begins again.

This means that the average arc voltage may not be an ideal
indication of the torch height in all conditions (material,
thickness, feed rate, amps, target height...). The author proposed
using the "peak low" (the base of the sawtooth) voltage as this best
represents the actual height under varying conditions.

Got an extra op amp for an averaging peak (or valley, in this case)
detector Mariss? Seriously, his design will probably do the trick
just fine in the real world.

Tom Scarince