MGL Avionics User Forum

I have a IEFIS Lite installed my Sonex. It read perfectly for about 10 hours then today on a cross country I realized it's stuck at 80MPH.

What's odd is altitude is reading perfectly. I had issues with this pressure sensor when I bought it. The sensor was pushed off the pads and I sent it in for repair. I zeroed the ASI and it gave me 5MPH, So I get 85MPH that's it.

I have a pitot tester and I tried a calibration with no luck. I suspect the pressor sensor crapped its pants? Or is this a software issue? I have ordered a new sensor and will drill the hole on the bottom and report back, but i have a feeling this is a software issue because it stops at 80 and reads perfectly fine up until that.

Yes that does sound like there is an issue with the sensor - in particular if it did break off in the past. The sensors don't really give issues so I don't think it's faulty - have a closer look at the pads that broke - I suspect one of them is not connected properly.

The sensor is analog - it produces a DC voltage at its output depending on pressure between the two ports - you can easily verify that with a voltmeter and applying a bit of pressure to a port. The sensor only needs 3.3V DC and ground to operate. Nothing else. So only three pins are actually used. The output goes to a tiny 6 pin IC close to the sensor - you can't miss it. That ls a ADC, analog to digital converter. That appears to be working from what your describe. It connects to an I2C bus that is also used for the AHRS, altimeter chip on the same PCB and since your altimeter is alive we can assume the I2C bus is alive and well.