Linearity from the 1950's

[woodchips]

Photos of a pot from some piece of aircraft navigation equipment from the 1950's. Can't at the moment remember what it came from.

As you can see it is a pretty normal wirewound pot, until you look closer and realise the circle of screws is in fact a set of trimmers to slightly adjust the position of the wiper to correct for linearity errors in the resistence winding. The greased track has a follower which acts through 90 degrees to push the wiper mounting frame side to side. To those who have used a boring machine, it is a similar arrangement used to linearise the machine scales.

An impressive piece of engineering, wonder what it cost. Now replaced by an optical encoder and an EPROM. Such is progress.

[calexanian]

Pretty good looking. However I wonder what the people who made that would think of a modern hall effect sensor or optical encoder with no moving contact to wear out. Still a really nice piece of engineering.

[cdev]

 I have a bunch of polyvaricons (inexpensive variable capacitors) which internally are quite complicated - despite their low price they have extensive adjustment capability so each of the capacitance ranges can be fine tuned. Its common for variable capacitors used in analog radios, even current models to have fine adjustments so that their tuning matches the markings on the dial..