The original post was actually concerned with how to make a decent
electronic level indicator.

If the level indicator is used in the normal way that a bubble
level indicator is used (i.e. to measure inclination of a stationary
object, such as a table top or brick wall), then you can make
a quite simple one using a potentiometer. You start with a flat base.
This becomes the part that will rest on the surface whose inclination
you want to measure. At a right angle to the base you attach an
upright that is several inches tall. Mounted to this upright
is a standard linear pot. Something in the range from 1k to 50k
would be fine. It is not important what the pot's value is, but
you want a pot that has low friction at the shaft.

The body of the pot is firmly fixed to the upright. Rotate the
pot to the approximate center of rotation. To the pot's
shaft attach a stiff metal rod that has a reasonable sized weight
attached to the far end of the rod. Connect one side of the pot
to ground, the other side to a voltage source, such as +5 v.

Output is measured between the ground and the wiper of the pot.
Let's assume you are using a PIC to measure the inclination angle.
Place assembly on a known flat surface. Push "level" button.
PIC reads voltage and stores it as zero reference. Incline
unit some predefined calibration angle, such as 30 degrees.
Push the "calibrate 30" button. PIC measures voltage, finds
difference between level and 30 degree values, divides by 30 and
comes up with the delta value per degree of inclination.

Now, as the device is placed at various degrees of inclination,
the PIC reads the current voltage, subtracts it from the
reference voltage, determines +/- , if it is negative, then
a minus sign is displayed and the value is converted to its
positive equivalent. The current delta value is divided by the
delta value per degree and then this value is displayed on the
readout in degrees.

Instead of a PIC you could use a couple of op amps and a few
trim pots to adjust zero point and circuit gain so that the
output voltage would be scaled to something like .1 volt per
degree. You could drive an analog or digital voltmeter
direct with this arrangement.

Fr. Tom McGahee

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