Voltage Tolerances

[Bill Hickey]

It would be wise for us all to remember that Heath engineers were renowned
for tolerant
designs and specs.  For example: most of their "modern" test equipment had
input line
voltage specs of a minimum of plus/minus 10% of nominal (usually 120VAC)
which meant
the unit would operate properly from 108-132 VAC input.  This also means
the inside
voltages would vary significantly.  Indeed, looking over many of the
manuals I have, they
are VERY careful to warn the troubleshooter that voltage measurements could
vary by
at least 20%.

Most of the time, the design tolerances were such that the equipment would
be able to
exceed these factors by some margin and still function....Heath engineers
were VERY
conservative with their specs.

If you go around "fixing" all your gear to handle our supposedly higher
modern line voltage
(and I go back a while .... we never saw less than 110-115 even when the
power draws were
high) how do you suppose it might react to modern utility techniques of
reducing line
voltages to homes for power conservation measures?  I suspect that even
with all these
other factors to consider, almost everyone's line voltage will fall within
the 108-132 VAC
spec that they have typically used (with 120VAC as the "nominal" value).

"If it ain't broke, you probably ought not to try to 'fix' it."

73,
Bill Hickey
WA3H

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