I folks, I have been digging around the forums and the 'net, and I THINK I found what I need, but I'm not sure. What I'm trying to do is read the absolute angular position of indicators on aircraft gauges. Specifically, I am trying to convert synchro/resolver-based instruments (which require 400hz AC and have no straightforward PC interface) to simple DC motors and circuits. Some of these gauges are infinite-turn instruments (like a compass card).
I am needing some guidance: first, I see devices like this (found on the forum): Hall-Effect Multiturn Absolute Encoder MAB40APM which look REALLY promising...even the enclosure style is the same as all the instrument synchros I've been working with. Question: when a device like the MAB40APM series say they can be programmed up to 200 turns, does that mean the device would make 200 turns before the return voltage on the analog output drops from maximum to minimum? Or does it follow a sine wave, where the voltage ramps up to maximum at the halfway point of travel (100 turns, for example) then tapers back down to 0.25v or so (which would not quite be absolute, of course, as you'd have to keep track of which phase you are in)? In my case, I would probably want the start/stop points to be set to just one turn, as I have other ways to count number of turns on most instruments (in the case of a compass card, for instance, I would not even need to count turns) and this would provide the most precision. Or am I misunderstanding something here?
Second question: what is a good source for reasonably cheap sensors in various sizes? Ideally they would feature a design similar to the one I linked to, so I could remove the old resolvers entirely and use the Hall sensors as drop-in replacements (at worst, I can gut the old resolvers and mount the new Hall devices inside them). Everything I'm finding so far that is close to what I need seems to be special order/pricey.
Third question: Has anyone played with using air core motors to sense position? I am using them to position simple single-needle indicators with light loads (such as airspeed indicators) and they are AWESOME for that. I am wondering if it's possible to run a current through the coils and read the return voltage to sense their position. At the moment I don't have any motors to experiment with (they are driving gauges in my old flight simulator).
Thanks!
Matt