Yep. Thank you Wolv, I had never gotten back to edit it again lol
Ok so with the new charger on the edge of being complete, the ammeter's linearity and offset from thermal effects need to be hammered down, as the first pass with the ammeter in particular had some significant linearity issues. I believe they've been resolved for the most part but it's much more difficult to verify of course than the voltage was, so I came up with this quick "hot wire shunt" that is set up to multiply a 50mV/250mA d'Arsonval type meter to be interpreted as 0-50A instead. Seems to check out in its roughest form on the bench, the tap points will of course be soldered and the assembly made to be a little more concise and robust so it doesn't introduce excessive drift of its own (it's by far not an ideal layout but will tell me approximately what I need to know to reel the charger's ammeter in to within reasonable tolerance for as far as I really care to try and chase the errors.)
This is after all something of a proof of several concepts type deal, I've got other things to compare it against. But more on that once it's finished... here's the experimental setup used to find the length of wire needed and starting points for the taps...
Some of the finer details that need to be observed when making one of these... the main ones being that the taps must be both *entirely* on the shunt wire and *only* the shunt wire to eliminate the variances caused by the connections to the source/load (in this case the EU barrier), and likewise for similar reasons, the location that the mV readings are taken from at the d'Arsonval, *after* the connections that lead to the taps. Might not intuitively seem like it but the internal shunt for the intended 0-250mA scale has radical effects on the voltage readings taken from across it, even tho it's a significantly higher resistance than the wire.
Here is the setup reading 5.00A, being fed by a linear bench supply operating in CC mode...
Variance is in the range of 20-40mA as it sits, checked at a dozen or so random setpoints within the 0-5A range. Each tick mark on the analog meter represents 1A.
I'll post the finished jig after I solder it up and get it in line for its intended use.
