Erratic Tach Readings

[dahugo]

Gentlemen,

I am stumped. I have the FlightDEK 180 installed in my RV-9a with an IO-320 engine. I properly installed the P-lead pickoff from the engine magnetos, and have 30kohm resistors in line between the ignition switch and the Dynon.

Several weeks ago was the first time we fired up our engine, and everything worked great except the tach. It read 1/2 the expected value. A quick look at the Dynon FlightDEK 180 installation manual showed this to be no problem, requiring only that I adjust the PULS/REV up or down to get the tach right.

Well, today I went to the airport for the specific purpose of doing just that. I hauled the plane out of the hangar, disconnected everything from the engine, and fired it up for the purpose of adjusting the PULS/REV on the tach to get it right.

Problem is, the tach was now reading 0, meaning nothing, or fluctuating upward toward 350 or 360. Now, at idle I can see 360 being 1/2 what the engine is actually doing, but why was I reading 0 most of the time?

I cannot imagine a short or disconnected wire somewhere, especially since on occasion today it would read 350 or 360.

Also, to increase the displayed RPM, do I go DOWN or UP on the PULS/REV?

HUGO

 

[jakej]

Hugo

PPR will be 1 or 2, trying different numbers won't hurt the Dynon. Tach reading 0 indicates you probably have an intermittent connection, maybe the resistor is broken.
Use your MM (multimeter) to check continuity while wriggling the wires.

HTH

Jake J

 

[mmarien]

If you are reading half the RPM then it's reading half the pulses per revolution that it needs. It probably is getting one pulse and is set for two per revolution. Switch the FlightDEK 180 to one pulse per revolution. That was the solution for the P-Mags with my Skyview.

 

[dynonsupport]

Gentlemen,

I am stumped.  I have the FlightDEK 180 installed in my RV-9a with an IO-320 engine.  I properly installed the P-lead pickoff from the engine magnetos, and have 30kohm resistors in line between the ignition switch and the Dynon.

Several weeks ago was the first time we fired up our engine, and everything worked great except the tach.  It read 1/2 the expected value.  A quick look at the Dynon FlightDEK 180 installation manual showed this to be no problem, requiring only that I adjust the PULS/REV up or down to get the tach right.

Well, today I went to the airport for the specific purpose of doing just that.  I hauled the plane out of the hangar, disconnected everything from the engine, and fired it up for the purpose of adjusting the PULS/REV on the tach to get it right.

Problem is, the tach was now reading 0, meaning nothing, or fluctuating upward toward 350 or 360.  Now, at idle I can see 360 being 1/2 what the engine is actually doing, but why was I reading 0 most of the time?

I cannot imagine a short or disconnected wire somewhere, especially since on occasion today it would read 350 or 360.

Also, to increase the displayed RPM, do I go DOWN or UP on the PULS/REV?

HUGO

Hugo:

The advice from Technical Support is that you have two problems. The first is an intermittent connection, which would explain your fluctuating readings.

The second issue is getting a correct Pulses/Revolution set. As JakeJ and mmarien suggest, changing the PPR setting won't hurt anything. Your engine manual is the definitive reference for correct PPR, but common values of PPR are 1.0, 1.5, and 2.0.