John said: "use a tooth counter sender off the ring gear" >From observations that is the hardest style to have as a primary or secondary due to the bracketing etc... to keep the air gap correct. Engine vibration tends to knock that one out of reading. Volvo and Chrysler both have used that method as an engine speed sensor, and wear on the ring gear from starters, dirt and such effect it. The best solution if not the coil attached tach, is the Tiny Tach that uses an inductive pickup off of one plug wire. We used these pickups with our Sun Scopes for years with no trouble. It clips around the plugwire and reads the pulses to a digital display. Very simple and reliable. In practice I have not seen any tach failures, and those reported that did fail, did not cause a total ignition failure, just quit reading. Diodes are a couple of bucks each, so applying 2 in each line insures against total failure, and should last a lifetime of flying anyhow.
Colin Rainey Independent Loan Officer Branch 2375 Apex Mortgage Company 386.615.3388 Home Office 407.739.0834 Cell 407.557.3260 Fax brokerpi...@bellsouth.net
