Would it be possible, is to use a potentiometer with this card?
it Would Be more accurate and less expensive.
I assume you're talking about using a potentiometer for the plunger sensor. It would be possible to use it with this *card*, but not with this software - the software is specifically written for the CCD. It's open-source, though, so you're free to fork the code base and add potentiometer plunger support if you want. The card has an ADC input, which could be used to read the voltage on the pot and thereby deduce its position.
A potentiometer would be less expensive, but more accurate? Could you explain your thinking there? I can't imagine how a potentiometer could be anywhere near as accurate or as precise. The CCD gives an absolute position to about 1/50 of an inch (with the default settings in the software - the device itself actually has 400 dpi resolution, but for the sake of faster read cycles the software I only sample at about 50 dpi). By absolute position, I mean that each pixel has a fixed position in space relative to the plunger, so there's simply no possibility of calibration drift. Potentiometer joysticks are notorious for calibration drift - they're sensitive to things like temperature and variations in the reference voltage from the power supply. And it would be hard to get precision at the 50 dpi level - if you tried to digitize the voltage that finely you'd probably see a lot of jitter from thermal noise.