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Old 01-20-2021, 11:47 AM
BobTurner BobTurner is offline
Join Date: Dec 2011
Location: Livermore, CA
Posts: 7,283

Originally Posted by TASEsq View Post
Thank you for the explanation. Makes sense.

What about the 0.5v voltage drop maximum? I didnít think you were allowed to have more than this due to the heat increase in the wire would be too much?
You can calculate the heat generated given the voltage drop AND other information, e.g., how long is the wire, what gauge. But what you really want to know, with respect to melting stuff, is how much heat is generated per inch, per foot, etc. Since the same current flows thru the entire wire, no matter how long, you can make that calculation knowing just the current and the resistance per foot. The voltage drop is of more interest for whatever device youíre trying to power. For example, if you are powering LED nav lights, and only get 1 volt out to them, they wonít work at all. Not dim, zero.

Just a small correction to a previous post: unless your airframe is built out of a superconductor, it has some resistance, just small. Unfortunately that resistance often grows as the airframe ages, tiny amounts of oxide build between lap joints, etc. Hence itís usually recommended that sensitive circuits, like audio lines, do not use the airframe ground but rather a separate wire back to a single point common ground. Without knowing anything about the electronic regulation circuit in this pitot tube (assuming there is one) it is hard to make a definitive statement as to how much, if any, ac noise it might be generating. But my guess is that the noise is little or none, and using the airframe as ground is unlikely to cause noise issues here. Thatís what I did.
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