Brief Description: RPM Measurement Using Hall Effect Sensor - Part 1
The traditional RPM sensor on aircraft is a cable (mechanical not electrical) that comes off the back of the engine and drives a mechanical instrument on the panel. Its all very 1930's. There are transducers now that you can get that connect to the same RPM cable output and connect to an electronic sensor.
Alternately, there are these special Hall Effect (a coil that generates an electronic pulse when a magnet is passed by it) sensors that can be connected to one of the vent ports on the magneto's. They are manufactured by Westach Part # 720-14R and are available from Aircraft Spruce. When the magnet inside the magneto spins, as it passes by the hall effect sensor it generates a pulse. This pulse can be counted over a time period and the RPM of the engine measured. An all-electronic solution with no added moving parts. Sounds good to me! I added a probe to both the left and right magnetos. Currently the EIS-4000 engine monitor only supports a single RPM sensor, but GRT is saying they will eventually they will support dual inputs. In preparation, I added two probes and wiring all the way back to the EIS-4000 unit.
Westach Part # 720-14R - Available From Aircraft Spruce
