Maybe I'm missing something here... If so, somebody please point it out. I posted under another subject in this forum (Erratic PBS-RPM Reading) about using this device on a Zenoah G-62 Magneto Ignition gas engine over a month ago. At first startup, I was seeing an RPM reading of over 12,000 rpm on an engine that was actually running at 6,000 rpm. Throttle response was also erratic. Since then, we tried a maiden flight, during which the engine went into "full throttle" mode, and we lost partial control of the aircraft. We were able to kill the engine and get the aircraft back safely.
Since then, we have done some bench testing with new servos for the throttle (with the PBS-RPM module still connected), and each time lost all contact with the throttle at anything over 1/4 throttle setting, and the throttle servo went to "full throttle" & locked out. We also lost all ability to control the flight surfaces as well.
The PBS-RPM unit was removed from the aircraft completely, and the engine was restarted. We regained full use of the throttle servo and all the flight servo operated completely normally.
It would appear that the use of the PBS-RPM sensor in conjunction with ANY magneto ignition engine will result in SEVERE RFI / EMI interference with the receiver, leading to possible loss of control of the aircraft, unless the sensor is optically isolated from the receiver. All my other gas engines are CDI ignitions, and use optically isolated devices for either telemetry or engine kill switches... so I do not have a problem in this area.
So, am I missing something here? Should I be using some other device, or connecting the sensor differently, in order to use it safely?
Any suggestions or workarounds?