PSI meter for RO/DI system

[ScubaSteve]

Basically you're wanting to make a Bourdon tube pressure guage. I really recommend just buying one. One of the things I had to do early on in my engineering career was actually build aa bourdon guage. Let me tell you: not easy. It's like being a jeweler.

Look around, you can get them pretty cheap. I pick my up for work for about $15 each. Granted that's from a local supplier that deals only with research instutions, by the actually mark it up more because they know we'll pay for it. If you want a DIY project, I'd say go try making a digital pressure guage. Way easier and much more fun to build.