I think there are accuracy gains measuring real (high) current and volt drop. Measuring the resistance alone with a fluke 77III results in a a reading bouncing between 0.4 and 0.5 ohms. That difference represents a 0.5v variation. i.e 2.0V - 2.5V Applying 5A, the volt drop was only 1.25V - 1.26V. I am tempted to believe the 1.25V drop reading where as I see the 0.4 - 0.5 ohms as a ball park reading. It just occurred to me I forgot to subtract the probe resistance reading, (need to repeat the test) but in the case of measuring volt drop (and current flow), the probe resistance has less impact. For reference the values above were measured using approx 4m of single core cat 5 where all 8 conductors were twisted together at one end with two groups of 4 conductors twisted together to provide the +ve and -ve leads at PSU end. Justin On 13 October 2017 at 19:59, Jason White wrote: > The temperature coefficient of resistance for copper is rather small: > 0.4%/C, it takes a 25C temperature rise to get a 10% increase in > resistance. > > If you want to account for heating's effect on wire resistance, just assu= me > that resistance is something like 10-20% higher than measured. > > On Friday, October 13, 2017, Justin Richards > wrote: > > > Quote:- > > Or maybe easier to measure the resistance of the wire and just multiply > > by that max current expected to give you the voltage drop. Also there > > > > > > I figure resistance measurements dont account for heating effects. > > > > I will do both out of curiosity i.e measure resistance then calculate > based > > on volt drop for a given current. > > > > Justin > > On 13 October 2017 at 15:49, Jim Ruxton > > wrote: > > > > > > > > > Volt drop over length. To test this I was going to double the lengt= h, > > > then > > > > using my trusty Bench PSU limit current to Max expected then place = a > > > short > > > > at far end and measure the volt drop. Sound feasible.? > > > Or maybe easier to measure the resistance of the wire and just multip= ly > > > by that max current expected to give you the voltage drop. Also there > > > are specs and tables that will give you the resistance of various gau= ge > > > wires. You can add a safety factor to that to be sure you are covered= .. > > > Jim > > > -- > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > > View/change your membership options at > > > http://mailman.mit.edu/mailman/listinfo/piclist > > > > > -- > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > > > -- > Jason White > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .