Thanks Phil, The link to stage 2 shows the best of all sending units I've been able to make. It is the most stable, the most simple, the most accurate and will be extremely long-lasting. But due to the increase in the cost of brass and resistance wire lately it can't be made economically and therefore I'll have to wait to start making these for sale.
And please...anyone who is buying a sender unit, consider the 0 - 30 ohm units sold on eBay by a seller whose ID is renbusan. I've said for years these are the best of all available options and they are far superior to the ones being sold by the usual suspects of vendors out there. Recently a friend asked "why are these better?" They're better for a few reasons. One, the body is made of nylon and the circuit board of fiberglass. Two, the wiping surface is flat and vertical. That is infinitely better than the semi-circle arc type, but is more difficult and costly to make and with the arc somebody making senders only needs to come up with one. "One size fits all?" Well, no it actually doesn't. It leads quickly to inaccuracy and failure. Three, the wiping surface is made of tiny metal pieces, rounded on each end which are bonded to the fiberglass and which begin set into a poured-in-place resistive compound. Very accurate and a clever design. Four, it is made in Taiwan and it was designed by somebody who knew exactly what they were doing. Take a look at the image below. Increase the size if you can and you'll see what I'm talking about when you look at the metal fingers. This is the unit:
