I need a low cost water pressure sensor. 100PSI.
Other than the fact that you need to measure 100psi of water pressure, your requirements are too vague for us to supply anything resembling a good answer. However, do a Google search on “water pressure sensor”. Here is the first hit on that search: http://www.circuitcellar.com/library/pr … -184/4.htm
Freescale have a range of pressure sensors that might fit your match…