A side note here. For a geezer whose background extends back into the
tube era, er, valve era, the expression "carbon composition" brings to
mind the matter of stability.
Some users on this list may be attempting precise, repeatable,
measurements with jigs. Those users should be aware that carbon
composition resistors, in the past, could not be trusted to hold their
value. They demonstrated a very distinct drift toward a higher value.
The drift could be rapid. That change in value occurred not just in the
hard service seen in tube circuits but while brand new and sitting in a
parts drawer. In our ignorance, we used to conjecture that the material,
compressed during manufacture, was expanding minutely over time and so
causing a drift to higher resistance.
If relaxation of the compressed material is really the issue, then it
would be reasonable that there would be a change in reactance, too.
John,
at radio station VE7AOV
+++++
On 2021-07-18 9:09 a.m., Roger Need via groups.io wrote:
An interesting discussion about lead inductance and shunt capacitance of carbon composition, carbon film and high wattage carbon resistors in this article by Bob Botos of HP.
Roger
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