[robert Spicer]

I am currently inspecting a 2006 RV 8A. The tachometer is a UMA electronic tachometer (P/N 19-806-116} with an hour meter. It is wired per Van's drawing to an ACS ignition switch with start. During runup we can get proper magneto rpm drop on the left magneto and indication of the drop on the tachometer. When checking the magneto drop on the right magneto we can hear a slight drop on the magneto but no indication ( 0 rpm) on the tachometer. I have read on the UMA instructions that a SPDT toggle switch can be installed. Has anyone in the air force encountered similar problem and have you installed the toggle switch to solve the problem?

If so please let me know. Thanks.

 

[planenutz]

What you have there is a fairly common setup on aircraft using an electronic RPM indicator. Do a search of the forum on this subject, Robert, and you'll find a number of threads on ways to deal with this. You can install a switch as you suggest, or you can install a different sensor dedicated to providing an RPM signal that is not dependent upon the magneto switch. Personally I prefer the latter - I have one engine with a hall effect sensor on the magneto and another engine which uses a sensor on the engine Tacho shaft output.

There are many ways to skin this cat.

 

[Southern Pete]

The tach you have is a pulse counter, you must supply a stream of pulses from each mag for it to count
See this page uma tachometers
UMA are quite responsive on email as it seems your instrument is no longer produced.