Golden Jubilee
Posts: 590
Joined: Mon Apr 06, 2015 11:00 pm
Location: SLC, UTAH
Re: Ohm reading for fuel sender?
Now this bit is somewhat speculative, but I suspect the principle is sound: The gauge itself is a heater which bends as the current (and heat) increase, which causes a deflection of the needle. In electronics your resistive losses, or copper losses, are current squared times resistance. Run the formula around and it would seem that the losses (heat, and therefore needle movement, ignoring the potential nonlinearity of the bimetallic strip itself) are proportional to the square of the current, i.e., nonlinear, so the sender and gauge kinda balance out. The fun part is that in the real world of 1950s electromechanical gizmos, we’re probably getting close but not exact, which is good enough for not running out of gas, which is the whole point to begin with. When you think about it, it’s amazing this stuff EVER worked to any degree of accuracy.
I will kindly disagree about using a non-pulsed IC voltage regulator, though. A few months back I converted to 12V and wanted to keep all my gauges. Figuring that the 6V system charges at about 7.1V, I set up an LM317 regulator for that value. It feeds the supply bus to the gauges via the ignition switch. Works perfectly, or at least as well as it ever did. The gauges still “see” the same voltage as before, so that’s to be expected. Results may vary depending on your application, of course.