Dennis

I started with an empty tank, then added 5 gallons at a time.  This way you can calibrate the probe to the gauge.  When the gauge reads full, you can figure how much fuel you use before the gauge starts to indicate, assuming you know how much fuel the tank holds

Your question asked how many gallons in the tank before the probe shows an output.  I assume that you are starting with an empty tank???   This depends on the attitude  of the plane.    To simplify the problem, once I knew how much the tank held, I just drained the tank and measured what came out.  In my case, each tank retained 1/2 gallon.  In practice I never let a tank get below 10 gallons, so this was rather academic.

Hope this helps.

Bill H

On Apr 18, 2012, at 8:00 AM, Dennis Ramsey <doramsey@gmail.com> wrote:

> I am trying to calibrate the fuel probes on my IV and trying to determine when I should see an indication on the fuel probes.   Can other IV builders tell me how many gallons they had in the tank before they saw a increase in output from the fuel probe.   I have the EI P300C probes.