1:Some people have had trouble because a few potentiometer manufacturers play games with the linearity specifications. Occasionally some potentiometers which are marked ans sold as "1% linearity" or "0.5% linearity" fail for our purposes because this figure can sometimes be the algebraic average or the total RMS linearity over the resitance range. Thus, it is possible for a pot to be off as much as 10% in the first quadrant (It may be off -10% in the next). If you encounter one, it will calibrate at 45 degrees, but at 90 degrees will have an error of as much as several degrees. Obviously this defeats the entire reason for the project.

In my case I have had to buy several and test them all for each machine. The alternative is to spend $150 for an instrument pot. Many people have apparantly been lucky and had a good one on the first try.

"It depends of what your definition of 'linearity' is".

2: BE HONEST WITH YOURSELF ABOUT YOUR SKILL LEVEL! Attaching the sense pot to your faceting machine requires careful assembly. While the wiring is easy, if you are not comfortable with soldering, ask a friend, the neighborhood nerd, or the kid next door for help.

3:The schematic and descriptions, etc. are freely offered as a kindness so people who want to build a digital readout can have a chance to do it. While I am always willing to help someone with a question, If you want to change the schematic, substitute components, run it at a hundred volts, use a sense pot from an old radio you found, etc., etc. that's fine, but you are on your own and that's putting it politely.