Inexpensive piezoelectric diaphragms can be used as sensors to facilitate both nozzle height setting and bed levelling in FFF (Fused Filament Fabrication) 3D printers. A variety of probes have been developed by the authors and others to utilize piezoelectric diaphragms both under the build stage and in the printer head. The reliability, repeatability and sensitivity of these probes has been investigated along with such practical considerations as usability in different environments, the functional life of piezoelectric diaphragms in this use and what improvement to print quality may be obtained. A probe using a piezoelectric diaphragm has been developed and released as an open source product, this probe as well as kits for making probes are available and are proving reliable. The conclusion is that piezoelectric diaphragms are equal to or better than other technologies used for nozzle probing.