Although I had previously calibrated the capacitive fuel senders by setting the empty and full points, I still needed to fill the tank in 2 gallon increments to create the voltage to fuel level mapping. I started with an empty tank and created the first calibration point. I thought it was a little odd that the sensor showed 5 volts, but didn’t give it too much thought. I added the first 2 gallons, but the sensor still showed 5 volts. I was pretty convinced something was wrong at this point, but I added a couple more gallons to confirm. Sure enough, the sensor still showed 5 volts. I started to worry that the sender was outputting a bogus value, but I decided to confirm all of the settings first. Fortunately, I pretty quickly found out that I hadn’t configured the correct input pins on the EMS. I needed to switch from the default (pins 20 and 21) to the ones I wired the senders to (pins 22 and 31) and change the input type to capacitive from resistive. With that change, I was getting voltage values that made sense for both tanks (2.9 volts from the left tank which is probably around half full and under a volt for the right tank which had the four gallons I just added). Unfortunately, I now need to empty the right tank again to redo the calibration. I could try to drain the four gallons out, but it’s probably easier to just fly again and run that tank dry.
