Precision Electronic Levels - summary

If one were to build an electrolytic level, this would be a good sensor for it. The electronics are pretty simple. But I assume that one must use only AC currents for sensing angle, a slight complication.

If I actually do it, sure.

This is one of those few areas where a dead simple gadget can achieve such precision.

An odd thought: There was a burglar alarm design sold in the 1970s that used a silicon strain gage glued to the underside of the floor (especially the joists) to detect a person walking through. The maker soon disappeared; don't really know why. May have been too fragile or too temperature sensitive to be practical. (Silicon strain gages were new then.) Or, too hard to install in an existing building. Or, too sensitive to wind induced building sway. Or merely too hard to explain. A precision tilt sensor could do the same thing, and could be installed in a closet somewhere. The big advantage was that the sensor was not easily found or approached undetected, and that one could set the sensitivity to ignore small critters scurrying about and most pets.

Joe Gwinn

Very slight. Recall that liquid crystal displays (as found in a $1.99 multimeter from HF) also require AC excitation.

I designed stuff like that in those days. Signal processessing to reject false alarms was indeed the trick before microprocessors became common. It's still a good trick, but a lot easier to implement now.

Another approach was seismic. The sensors were geophones developed for oilfield exploration, basically a dynamic mike with a slug instead of a diaphragm. We made devices that could sense a man walking from a distance of several meters, a vehicle from several hundred meters or a chopper overhead, and it could tell the difference. It used a very small number of CMOS logic chips (less than half a dozen) to do it.