After a long delay I got an answer from a friend who is an engineer in the
UK electricity generating industry. He informs me:-
"There are no specified limits on frequency.
The normal variation is from 49.85 to 50.15Hz.
Load shedding takes place if it falls to 49.5Hz"
So I reckon that in the U.K. at least the mains frequency strobe method
would give you an accuracy of 0.3% if you avoid
obvious high demand times.
Another Idea:
Did you notice on the 'Air Show' programme (BBC-2 yesterday) that the
PA28 on base leg had the prop appearing to be running at 30 rpm? So try
watching your prop on a monitor / video camera set-up and see what you can
work out from that.
Eric Evers
Largs, Ayrshire,
SCOTLAND - UK
-----Original Message-----
From: Gramin@aol.com [SMTP:Gramin@aol.com]
Sent: 26 September 1997 20:11
Subject: Re: Calibrating Engine RPM
In a message dated 26/09/97 06:56:59, Mark B writes:
<< this all assumes that the mains are stablised at 50Hz!
testing here in south africa reveals that the supply can vary up to 5%>>
It does in UK too - but wave you fingers in front of the screen you are now
looking at and you will see a crystal controlled strobo 50 hz source
immediately. Bit more expensive if you chop it up in the blades though.
Graham C. G-EMIN
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