I'm trying to design a pickup/reluctor that produces a specific waveform. I'm using an automotive ignition pickup and expermenting with different shapes of reluctor but the results I'm getting aren't making any sense. The pickup/reluctor are of the familiar design with a pickup coil wound around a magnetic core and a ferrous reluctor moving past one end of the pickup core. First of all, I expected peak voltage to increase as rpm increased, but it's not, at least not in the range I'm looking at. Could the problem be the the impedance of the pickup coil dissapating too much power above a certain level? Secondly, it occurs to me that I might have better luck if I understood the underlying relationship between the reluctor position and speed and the change in magnetic flux in the pickup, but it's been too long since my college physics classes. Can anyone give me some hints or perhaps provide me with the basic equations to compute the change in flux?