Bob, You're right that conventional period, frequency, or universal counters have great difficulty measuring (timing) separate events that occur as fast as 60 Hz. A fine exception is the Pendulum CNT-90/91 which is a time-stamping universal counter. With a few simple GPIB commands, you get data on every rising/falling edge of an input signal. The resolution is 50 ps and the capture rate is 250k sps.
If anyone has been able to collect zero-deadtime per-cycle timing using, say, a HP 5370 or 53132 or SR620 I would be interested to know it was done. It might actually be possible, but I've not tried hard enough. The HP 5372A is another possibility. /tvb ----- Original Message ----- From: "Bob Camp" <[email protected]> To: "'Discussion of precise time and frequency measurement'" <[email protected]> Sent: Friday, February 22, 2013 5:34 AM Subject: Re: [time-nuts] Logging the grid frequency.... Hi Don't have a Picotest, but do have similar counters. It's very common for them to do what looks like a divide of the input frequency before they measure it. The net result is that you can't measure 60 Hz in 1/60th of a second. You measure it in 4/60th's of a second instead. The next problem you will run into is that the counter takes time to arm. Even if it did the measure in 1/60th of a second, you would only get every other cycle. One way to get every cycle is to measure time rather than frequency. You time tag every positive zero crossing and then do the math to get frequency. If you drive one input with a fixed 60 Hz square wave and put the line into the other input you can get the time offset between them. Another approach is to use two conventional period counters and let them each measure a cycle. One measures while the other is dumping data and re-arming. Bob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Daniel Mendes Sent: Friday, February 22, 2013 7:47 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Logging the grid frequency.... Hi, I have a Picotest U6200A. I´m trying to log the grid frequency (60Hz) to generate data for my work. I need to get data from every cycle. I setup their program (it always starts in chinese... very funny) but seems that it can only log every 100ms. Questions: 1) Is that a limitation of the equipment or the software? 2) Using direct comands, can I get data faster? Thanks for any help... Daniel _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
