Original poster: "David Thomson" <dave-at-volantis-dot-org> Hi Terry, Jan, and all, Thanks for your many suggestions. I located a HP 34970A and 34901A card at a reasonable price. Now how do I go about using a 555 timer for measuring magnetic field, inductance and capacitance? Is there some way to rig Hall effect chips to measure the magnetic field that isn't too complicated? Dave