I'm very new to instrument development, and would like to know if there aren't any recommended readings or books to assist with instrument development and testing.
Instrument development varies widely across different scientific disciplines. Since I work in astrophysics instrumentation, most of what I know may translate poorly to other fields. One book that I like and probably would find wider application is on detectors of light across a common wavelength range: "Detection of Light: From the Ultraviolet to the Submillimeter" by George Rieke.