Hi, I have done some testing of the accuracy of the mains frequency (for possible use in calibration etc) and thought people may be interested in the results.
Here is a sample chart of mains freq error over about 17 minutes logging time;
And there are a couple of proposed systems for generating accurate 1 second clock periods phase-locked to the mains frequency but still able to tolerate faulty mains cycles, glitches etc and short term complete loss of mains frequency;
And this system below generates each second with a high stability (always less than 50 PPM error) but always generates the same long term accuracy as the mains freq, for clock use etc;
The same page also has some other info about testing the xtal accuracy against a GPS reference;
http://www.romanblack.com/onesec/High_Acc_Timing.htm
Here is a sample chart of mains freq error over about 17 minutes logging time;
And there are a couple of proposed systems for generating accurate 1 second clock periods phase-locked to the mains frequency but still able to tolerate faulty mains cycles, glitches etc and short term complete loss of mains frequency;
And this system below generates each second with a high stability (always less than 50 PPM error) but always generates the same long term accuracy as the mains freq, for clock use etc;
The same page also has some other info about testing the xtal accuracy against a GPS reference;
http://www.romanblack.com/onesec/High_Acc_Timing.htm