The zero crossings of waveforms as well as those of derivatives and other functions of these waveforms are easy to determine with rapid and inexpensive digital encoding for processing by personal computers. Methods are supported by mathematics, which is necessary if theory is to be extended to unfamiliar areas. Measurements are almost independent of amplitude scaling and are repeatable. Phase I research will explore applicability of zero crossing methods to a variety of instrumentation tasks, including those involving multiple waveforms where cross- correlations are of interest. Mathematical models and methods will be extended and signal sensing and conditioning apparatus will be adapted for personal computer input. Zero crossing analysis is comparatively understandable by the specialist not skilled in mathematics. The longer range commercial objective is a family of low cost analytical instruments with attachment to the standard office computer with normal video display and associated printer. Widespread availability of additional instruments producing hard copy records will generally improve patient care and serve the needs of preventative medicine.