I think we've seen too many threads asking identification for an unknown inductor or transformer that people salvaged or found. This makes me curious if there is a way, although limited, to get a certain usable specification out of it using non destructive method ?
Non destructive here means without the need of cracking the core which sometimes is fully epoxied or potted, or need to unwind the wires, all data gathered only through it's termination points and external physical inspections.
Assuming we have these pre-conditions before we start the probing :
Tools :
- A decent LCR meter like those popular handhelds such as MS5308, DE-500 or similar.
- An inductor saturation tester for finding the current saturation point, like this example ->
HERE.
- A scope and/or sig-gen, maybe ?
Inductor/transformer physical informations :
- Ability to measure or at least take an approximation of the wire diameter size from the termination points.
- Winding count and tapped count if any.
- Core's shape/size/volume.
- Winding topology if they're visible from outside like overlapped, stacked windings and etc ?
- Anything else that I missed regarding the needed info from the physical inspection on the inductor/transformer ?
Understand that there are limits on inductor specifications that we can gathered for example like the important factor isolation and creepage limit and etc.
Questions :
Aware the outcome definitely will not 100% accurate, is this doable ?
Can we somehow get "good enough" specifications to re-use the inductor/transformer later for one off project if needed someday ?
Of course the user also required to be aware of the risks involved like lacking of the isolation limitation info and etc. For example its not wise to use in a thousands volt circuit, or for welding (high current) using a small iron core transformer salvaged from a cheap a wall wart AC to DC converter, or a power ferrite inductor from those cheap car DC->USB cellphone converter/charger to be used in 1000 watt power switching circuit.
PS :
Please see this question in the context of enthusiast/hobbyist perspective, understand that these activity probably will be useless in commercial/pro environment, since it will be much more economical to buy an off shelf ready product which fit in as required by the circuit. But for pack rat like me that love to salvage used inductors/transformers, I will be more happy if I can identify and use them even though not 100% suitable but still acceptable, compared to buying a new inductor even its cheap. Hoping I'm not alone here.