On Thu, 23 Jun 2016 11:43:19 -0400 Lennart Sorensen via talk <talk@gtalug.org> wrote:
On Wed, Jun 22, 2016 at 07:39:34PM -0400, Michael Galea via talk wrote:
No, the device is not a UPS. It is a PLC that measures voltages, currents, real and reactive power of a 3-phase service. It provides me the results as IEEE754 32-bit floating point numbers. It's me that truncates to 2 digits. You know I'm sorry I ever implied that the grid wasn't long term accurate at 60 Hz! What I should have said was that in the short term the grid could be quite off 60 Hz but over the longer term it could average out. If I really needed to know the answer to the question of "how much out", I would get ask the PLC to just count cycles and send me the count with a timestamp. That would tell. Well wikipedia claims the grid can be off by up to 10 seconds in north america on this side of the continent. The west and texas allow a lot less. So it can certainly be a bit off for quite a while.
this is a very interesting thread, i frequently ponder personal grid timing and other cycles using various oscillations, until the old 40Hz streak lights up (sync) my life