I recently acquired a non-working Fluke 80i-410 DC & AC 400A clamp meter.
The output lead had been severed at the strain relief; the battery compartment was badly corroded and the batteries had obviously swollen to such a degree that the case was shattered; and the wires from the PCB to the battery case and the Hall effect sensor were compressed and partly severed in the rear lamination gap.
It was a real pig to dismantle as the hinge pin is an interference fit in the hard plastic (phenolic type) body and there was a danger of shattering the whole shebang. I am unsure of the vintage but it must be late 80s-early 90s (It was nice to see waxed lacing cord holding the output lead to the PCB- Ah, memories...)
I replaced the output lead and made good the wires, then temporarily soldered a 2X AA battery holder just to check if the meter worked. All seemed OK apart from a very small zero offset. On this meter because of the high range (5A - 400A) there is no user zero adjustment for offset. I wound ten turns of a test lead through the jaws and ran 2A through it- the reading appeared to be about 30% high. There are two multi-turn pots by the output lead which are accessible from the outside. I assume that they are for zero and span adjustment.
I spent an afternoon repairing the battery case with a sim card carrier, epoxy and stainless wire (from a chicken feeder!).
Before I dismantle it again to draw the schematic- does anyone know of any pitfalls or 'gotchas' in calibrating this type of meter? I intend to wind 100 turns of wire around a former (two plastic lids glued together or a small toy wheel) then pass 4A (AC & DC) through the coil with the jaws clamped around it.
Is this a valid process? For what I will use this for realistically it need not be better than 5%, but I would like to get it as good as I can.
Regards, BT