Calibrated Fuel Tank Senders

I calibrated the fuel tank senders today.  I’m using the Princeton two-point capacitive senders which are pretty straightforward to calibrate.  Here are the basic steps:

  1. Empty the tank (I had already done this when determining unusable fuel for the W&B).
  2. Power on the sender.
  3. Hit the set button to set the empty point.
  4. Fill the tank.
  5. Hit the set button again to set the full point.

The sender then puts out the full 0-5V range from empty to full.  This is much better than the Dynon capacitive senders which can’t be calibrated and generally put out a small fraction of that voltage range across the whole tank capacity.  The Princeton senders solve the dynamic range problem, but the voltage still doesn’t necessarily follow the fuel volume in a linear way.  The SkyView system solves that by including a separate calibration mechanism where you add fuel 2 gallons at a time.  Each time fuel is added, a button is hit on the SkyView to correlate that particular voltage reading from the sender with that fuel volume.  Unfortunately, this means that I need to start over with an empty tank to do the SkyView calibration.  Since I don’t have any interest in draining that much fuel out of the tanks, I’ll have to wait until I’m flying and can burn down the fuel.

I did this for the left tank by pouring fuel from gas cans into the tank, but it was very time consuming and I ended up spilling some gas.  Since I hadn’t run the engine in a month, I taxied the plane down to the pump to calibrate the right tank.  I used that as an opportunity to break in the brakes a bit more too.

Using the capacitive probes with the Princeton senders should result in a nearly perfectly linear fuel gauge reading across the entire tank capacity.  This is quite a bit better than the resistive senders which read empty when there is still a fair amount of fuel in the tanks and reads full well below the full capacity of the tank…

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