ElectroAir ignition tachometer output to Garmin

[dcat127]

I have a Saratoga that has the dual ElectroAir electronic ignition installed. It has a Garmin gi-275 engine monitor as well. The engine monitor has the tach turned off, and seemingly not connected. According to the ElectroAir manual it appears that it does have a tach signal output that is a 12volt square wave signal. It says verify that signal is compatible with your tach before installing. I cannot find anything in the Garmin manual indicating what signal it is expecting.

 

[Ryan Klems]

Assuming you probably have a GEA24/24B providing the data to the GI-275. It’ll work with P-lead signal for traditional mags, or a UMA mag pickup for slick or bendix
Mags, or a 0-5V square wave from a surefire tach2. The electroair is only supported with a GEA 110 interface, and only a single mag. The Electroair would interface with RPM 1, and RPM 2 would go to standard p-lead interface for traditional mags. So the dual interface is not supported with the GI-275 and either engine adaptor. How are you currently displaying RPM?

 

[dcat127]

The old mechanical tach is still installed.

 

[dcat127]

What is the difference between a Surefly 5 volt square wave signal and an ElectroAir 12 volt square wave signal? I mean ok obviously the volts...but changing a 12v signal to a 5v hardly seems to be an engineering feat.

 

[Ryan Klems]

It's less the engineering feat vs. what the STC approves as an interface. C.19 of the install manual lists approved EIS sensor compatibility, which currently lists 6 approved interfaces, of which two are Electroair (EIS-41000 and EIS-61000), with the note that it is approved with the GEA 110 only, and the interface drawings notate that the Electroair sensor can only be interfaced to RPM 1, and the normal magneto then to RPM 2. Whereas the Surefire Tach2 can be interfaced with the GEA 24 or GEA 110, and can be connected to either RPM input. I'm going to guess there is some reason for that (as opposed to some directions for a resistor build up or something), but I'm not privy to it.