Speaking of eBay

From: William Donzelli <aw288_at_osfn.org>
Date: Thu Dec 30 14:26:52 2004

> Not really true. The manufacturing process and resistor structure
> is fundamentally different. Film resistors are generally an insulating
> core, with spirals of the resistive stuff (thickness, width, and material
> depend on the resistance of course) around the core. Then there's a
> protective coating and marking around the outside.
> There are a few applications where the spiral structure has undesired
> inductive effects. But then there are different varieties of metal films,
> some specifically low inductance.

If a film resistor is spec'd to work at 600 Volts, and it is having some
problems up there, I would say it's crummy.

> I get the impression that the metal-film manufacturing process has seen
> all the benefits of manufacturing technology over the past few decades,
> while the carbon composition process has had no improvement for like
> fifty years. Mass-produced 0.1% metal film resistors are cheaper than
> 10% carbon composition units.

Yes, I agree. Carbon comp resistors are pretty much a dead technology.
> All resistors drift over time :-). I will admit that carbon compositions
> are much more drifty with respect to just about everything
> (time, temperature, heat cycling, humidity, phase
> of the moon, etc.)

It is quite common (seen it with my own eyes, too) for a 40 year old
carbon comp resistor to drift over 20 percent, and that even includes the
five percent versions.

William Donzelli
Received on Thu Dec 30 2004 - 14:26:52 GMT

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