Originally Posted by rags
Great info - thank you.
Your thoughts about the gold plating wearing off or in the case of tinned terminals, ten tinning wearing off and oxidation occurring that would increase resistance?
I just tested the aileron servo connector of that old airplane. Its contact resistance showed up as 0.0041 Ohms, IMHO pretty good after over a decade.
One thing of note, that connector is connected and disconnected repeatedly over the past years, providing a sort of cleaning action. Where that gold plating is important, is when those connectors are buried inside a wing as a servo extension, and perhaps left connected for years.
For those that are interested, the contact resistance was measured by applying exactly one ampere DC through the contact. That one amp was provided by a 18 Volt DC, 3 Amp power supply purchased through www.mpja.com
This power supply can be adjusted from zero to 18 Volts DC, and has current limiting adjustable from zero to three Amps. The voltage drop was measured by my Fluke 87V digital meter, set on the high resolution function of the millivolt DC range. This meter allows measuring DC volts down to 00.01 millivolts. The voltage was measured at the same place on the terminal, that is at the location where the wires are crimped into the terminal.
Moving that voltage measuring test location made a substantial difference in the millivolt level measured.
The exact contact resistance can then be calculated by the formula R=E/I or resistance equals voltage drop divided by amps. We used the same testing technique on contacts rated for 800 Amps at work, with commercial micro-ohmmeters designed for that function. Those micro-ohmmeters can cost as much as a wet turbine model.