Yes, 120V/60Hz in the US. As far as the long term spec, I don't know what it is exactly. I do know that the power plant control systems that we build have to deal with frequency control. This is done something like this: Normally power output of hydro generators is controlled by how much water you let them get. More water rushes in, it pushes the turbine harder, the generator tries to run faster, but can't (its phase locked to the line), so it ends up leading the phase of the line by a little bit, so it dumps lots of power onto the line. The more water rushing in the harder the turbine is being pushed the more the Now we can see that if a lot of generators are all trying to push the phase forward, eventually the line frequency will tend to go up a bit. This isn't a good thing. This is compensated by by adjusting the field strength of the generator so that its voltage goes up. Now it can create more power without pushing the phase as hard. So, by controlling both the field excitation and the water allowed in we can control both the output power and the phase push (and thus indirectly the frequency). This frequency control is a _big deal_ in the system specifications! Bob Ammerman RAm Systems (contract development of high performance, high function, low-level software) ----- Original Message ----- From: Vasile Surducan To: Sent: Thursday, February 22, 2001 7:00 AM Subject: Re: [PIC] Timer Tribulations > Just for comparation, you have 120V/60Hz isn't it ? > Have you an official info ( or a long time measurement ) how small > is the main frequency drift ? For me sound's incredible... > thank's > Vasile > > On Thu, 22 Feb 2001, Bob Ammerman wrote: > > > In USA long term mains drift is _very_ close to zero. > > > > The power grid will deliberately adjust the mains frequency to compensate > > for previous errors. > > > > Mains driven clocks keep good time nearly indefinitely (barring power > > failure, which is very rare except for local problems due to storms, etc.) > > [And California's problems due to stupidity :-) ]. > > > > Bob Ammerman > > RAm Systems > > (contract development of high performance, high function, low-level > > software) > > > > ----- Original Message ----- > > From: Vasile Surducan > > To: > > Sent: Thursday, February 22, 2001 3:26 AM > > Subject: Re: [PIC] Timer Tribulations > > > > > > > On Wed, 21 Feb 2001, Tony Nixon wrote: > > > > > > > You will find that the clock will drift one way or the other depending > > > > on temperature, so using the mains as a frequency source is much more > > > > accurate. > > > > > > You are certainly joking ! Or in your country mains frequency drift is > > > under 0.5% ... > > > > > > Vasile > > > > > > -- > > > http://www.piclist.com hint: The list server can filter out subtopics > > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > > > > > -- > > http://www.piclist.com hint: The list server can filter out subtopics > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics