[LAD] A little quiz about audio measurements...

[Ralf Mardorf]

fons at kokkinizita.net wrote:
> On Fri, May 28, 2010 at 11:24:29PM +0200, Ralf Mardorf wrote:
>
>   
>> Oberhausen, Rheinland, Germany; power line frequency right now is at
>> 49 Hz, measured with a low cost energy consumption costs meter.
>> Those low cost meters shouldn't be able to do correct measurements
>> ;). The best test at home might be to compare the sound of a
>> transformer with a 50 Hz sine wave.
>>     
>
> 49 Hz is impossible. It would mean that a clock using this
> frequency would be slow by more than a minute per hour. 
>
> Long-term accuracy is extremely high, precisely because clocks
> depend on it. And since almost all of Europe is interconnected,
> adjusting the frequency must be a _very_ slow process. So errors
> of 2 percent really can't be tolerated.
>
> Ciao,
>   

The meter is bad. As I've written before (I fetched your mail), you're 
right, the tolerance is < 0.2 Hz (< 0,4%), but 1 Hz (2%) ;).