How-to Calibrating your Aithre Shield 2.0 in a Garmin G3X Touch (experimental)

[Neal]

I've been having issues with my Aithre Shield 2.0 lately and have had dialog with Aithre's support which has been wonderful and very responsive. In figuring out what's going on with my G3X/GEA24 situation including erratic CO readings from Aithre a friend told me to use the Aithre iOS app and compare with what the G3X shows. Excellent suggestion, thank you @turbopilot, and it also indicated different readings on the iOS app (accurate info) and the G3X which was not accurate and requires calibration.

The Aithre installation manual is a little nebulous on exactly how to calibrate but it's been an interesting learning experience hence why I'm sharing this. The G3X via the GEA24 receives voltages from the Aithre which are converted into parts per million for a CO reading. So effectively a 0 voltage sense would be 0 ppm and a 3.3V sense would be 255 ppm (doing this from memory but I believe those are accurate). In my case the G3X was reading slightly high by about 7-10 ppm. I went to the configuration side of the G3X and into the Engine area and then found the CO monitor (can't remember how it's titled as the sensor) and then went to the calibration area. I removed the 0/0 entry and entered a new entry which I use a 0 ppm is a 0.15V value. I then saved the value and then saved the calibration. This worked great but it was too much compensation so for about a 7-10 ppm value half of what I entered would be correct, so for my next flight I'll use 0 ppm at 0.07V.

Interesting process but the key learning point here is bring up your Aithre iOS app and with it bluetooth connected to your Aithre Shield 2.0 device you can see the real numbers. Then from that you can calibrate your G3X touch to show a more accurate CO reading.

 

[Tsquared]

Does the engine need to be running when you do the initial reading prior to calibrate?

 

[Neal]

Does the engine need to be running when you do the initial reading prior to calibrate?

No, but yes. IBBS alone should power up the Aithre IIRC and you'll be able to connect to it with the app. But the problem is that will be a hard zero reading so you won't have anything to clue you in on differences. Per the Aithre website and/or manual you can calibrate using bamboo incents but not wise around fuel so what you need to do is run the engine and get some CO flowing either on the ground or just watch it in flight as you start seeing readings. Compare the G3X reading to the iOS app.

What I believe is it's about .01 volt per 1 ppm for calibration. In my case of being 7 ppm off between G3X (high) to iOS app with a lower reading setting my first (bottom level) point in G3X config would be 0ppm at 0.07V.

 

[Neal]

I had a failed Aithre and I'm pleased to share the amazing support by Aithre to warranty replace my 1 year old unit. We don't know the exact cause but yesterday I replaced the failed unit. Not the easiest job in my plane as the wires either need to be removed and replaced at the GEA 24 connector, very hard to access in my plane, or splice in, which I did. These type of splices are new using a different type of butt connector but it worked great. As always I have to do everything twice but got the job done and so far in the test flight it seems stable.

The calibration was needed both on the lower and upper end. During G3X startup the Aithre was only reading 251 at the top end which should be 255 and the lower end was resting at 5 ppm. So I had to delete and set both lower and upper ends of the scale and get it calibrated. We'll see how it works from here.

 

[Tsquared]

While flying yesterday I received a number of yellow and red warnings from my Aithre. This only occurred during run ups, climb outs and approaches. Numbers never exceeded 100ppm and went away in cruise or on roll out. In cruise, levels were zero. Testing with the app showed both devices within 1ppm.

What are others setting for caution and warning levels for their carbon monoxide detectors?

 

[Neal]

Silicone those gear attachment gaps.

 

[Neal]

As I learned in reviewing SD card data for my erratic RPM issue ongoing you can see the CO PPM readings when they alert in the data file. If you bring the SD card home and pull the data from your latest flight you can see the readings but also verify you're calibrated as when you power on the IBBS you should see it go to 255 and then settle to 0. If not then you need some calibration adjustments.