Low Resolution Tach Uses Dual Edge Technique to Boost Performance
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
A microprocessor-based dual-edge technique of analyzing a low resolution tach signal nearly doubles the effective resolution of the tach. The technique also utilizes a software phase locked loop to generate a higher frequency tach signal. This allows the performance of a higher cost tach technology to be achieved with a low cost technology. The duty cycle of a tach signal will change with the age of the sensor, tach wheel wobble, contamination, and original parts toler- Continued ances. This usually forces the use of the information contained in only one edge of the signal (leading-edge or trailing-edge). The following technique of processing both edges of the tach signal is insensitive to the above variations and allows a higher frequency tach signal to be generated with better resolution than a single-edge technique.