Comments on: Measuring the AC line frequency http://jeelabs.org/2009/05/28/measuring-the-ac-line-frequency/ Computing stuff tied to the physical world Mon, 06 Feb 2012 13:55:24 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: jcw http://jeelabs.org/2009/05/28/measuring-the-ac-line-frequency/#comment-115 jcw Thu, 28 May 2009 14:56:13 +0000 http://jeelab.wordpress.com/?p=1842#comment-115 <p>Ah, ok. It'd be nice to see some discussion about this in Europe. Perhaps there is, I haven't really searched further yet.</p> <p><em>(update: this was a reply to Reinhard's "The point is...")</em></p> Ah, ok. It’d be nice to see some discussion about this in Europe. Perhaps there is, I haven’t really searched further yet.

(update: this was a reply to Reinhard’s “The point is…”)

]]> By: jcw http://jeelabs.org/2009/05/28/measuring-the-ac-line-frequency/#comment-114 jcw Thu, 28 May 2009 14:54:50 +0000 http://jeelab.wordpress.com/?p=1842#comment-114 <p>Yes - I merely used the transformer because I'm a bit scared of high voltages :)</p> Yes – I merely used the transformer because I’m a bit scared of high voltages :)

]]> By: jcw http://jeelabs.org/2009/05/28/measuring-the-ac-line-frequency/#comment-117 jcw Thu, 28 May 2009 14:53:08 +0000 http://jeelab.wordpress.com/?p=1842#comment-117 <p>Yes, you'd want long-term accuracy. So the power company could perhaps "reserve" 49.9 .. 50.1 Hz for getting the long term average just right. Brief excursions outside this range could then be used for signaling.</p> Yes, you’d want long-term accuracy. So the power company could perhaps “reserve” 49.9 .. 50.1 Hz for getting the long term average just right. Brief excursions outside this range could then be used for signaling.

]]> By: jcw http://jeelabs.org/2009/05/28/measuring-the-ac-line-frequency/#comment-116 jcw Thu, 28 May 2009 14:45:38 +0000 http://jeelab.wordpress.com/?p=1842#comment-116 <p>I like it - works well for me. Am using it on Windows 2000.</p> I like it – works well for me. Am using it on Windows 2000.

]]> By: Reinhard Max http://jeelabs.org/2009/05/28/measuring-the-ac-line-frequency/#comment-121 Reinhard Max Thu, 28 May 2009 08:54:17 +0000 http://jeelab.wordpress.com/?p=1842#comment-121 <p>Atmel has an application note that shows a zero cross detector where the AVR connects to the mains line over two 1M resistors without a transformer or opto coupler: http://www.atmel.com/dyn/resources/prod_documents/doc2508.pdf . This of course requires sufficient electrical insulation of the device for safety reasons.</p> Atmel has an application note that shows a zero cross detector where the AVR connects to the mains line over two 1M resistors without a transformer or opto coupler: http://www.atmel.com/dyn/resources/prod_documents/doc2508.pdf . This of course requires sufficient electrical insulation of the device for safety reasons.

]]> By: Reinhard Max http://jeelabs.org/2009/05/28/measuring-the-ac-line-frequency/#comment-120 Reinhard Max Thu, 28 May 2009 08:37:36 +0000 http://jeelab.wordpress.com/?p=1842#comment-120 <p>The point is not that the frequency is changed deliberately, but that the frequency change which is already happening when supply and demand are not in balance is being used to switch certain devices on and off that have some flexibility as to when exactly they get powered.</p> <p>The power companies guarantee the nominal frequency only as a long-term average, so that clocks don't run off completely, but variations of several seconds back and forth during the day are normal.</p> <p>See also: http://en.wikipedia.org/wiki/Utility_frequency#Stability</p> <p>One potential problem I see with the dynamic demand system is, that the imbalance might swing up, because the controllers on the line side and on the load side are working against each other.</p> The point is not that the frequency is changed deliberately, but that the frequency change which is already happening when supply and demand are not in balance is being used to switch certain devices on and off that have some flexibility as to when exactly they get powered.

The power companies guarantee the nominal frequency only as a long-term average, so that clocks don’t run off completely, but variations of several seconds back and forth during the day are normal.

See also: http://en.wikipedia.org/wiki/Utility_frequency#Stability

One potential problem I see with the dynamic demand system is, that the imbalance might swing up, because the controllers on the line side and on the load side are working against each other.

]]> By: Stan http://jeelabs.org/2009/05/28/measuring-the-ac-line-frequency/#comment-119 Stan Thu, 28 May 2009 07:29:15 +0000 http://jeelab.wordpress.com/?p=1842#comment-119 <p>Off-topic question: I see you're using DSO-2090 USB oscilloscope.</p> <p>What's your experience with it? Is it any good? I am looking to get some DSO for myself, however there seem to be not so many USB DSOs available on the market with Mac OS X support. Any advice, thanks?</p> Off-topic question: I see you’re using DSO-2090 USB oscilloscope.

What’s your experience with it? Is it any good? I am looking to get some DSO for myself, however there seem to be not so many USB DSOs available on the market with Mac OS X support. Any advice, thanks?

]]> By: Andreas Kupries http://jeelabs.org/2009/05/28/measuring-the-ac-line-frequency/#comment-118 Andreas Kupries Wed, 27 May 2009 23:26:23 +0000 http://jeelab.wordpress.com/?p=1842#comment-118 <p>I seem to remember that there are electric clocks which derive their time normal from the power line frequency. Such clocks would start to run faster or slower when connected to a net modulating the power-frequency to transmit information.</p> I seem to remember that there are electric clocks which derive their time normal from the power line frequency. Such clocks would start to run faster or slower when connected to a net modulating the power-frequency to transmit information.

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