Re: [time-nuts] Looking for off-the-shelf device to timestampmultiple PPS inputs
Hi For milliseconds, route the signals into a hard wired parallel port (not USB) and sample the data. Looking at it 1K times a second is pretty easy. All software running on a tired old PC. Sync the thing up with NTP or what ever to keep it stable long term. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Kevin Rosenberg Sent: Wednesday, September 28, 2011 3:56 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Looking for off-the-shelf device to timestampmultiple PPS inputs On Sep 28, 2011, at 1:21 PM, Chris Albertson wrote: Milliseconds? So why are we talking about HP counters and PicTic and so on. A basic low end Linux system that is controlled by NTP and a GPS receiver is maybe about 100X better than your requirements. (I figure you are looking for about 1000 parts per million, NTP is way better then that if you have a local GPS) Heh! I suppose milliseconds don't really belong on time nuts, they're in the range of polling! But, for his needs, that's sufficient resolution. What would be nice is if the PPS times would just show up log file for him. Hence, the request about off-the-shelf hardware. But, as long as I'll be looking at buying some new hardware, I'd be glad to get resolution of nanoseconds or better. Probably best sigma for the price will be the XMega with 32 MHz input from Clockbox with a sigma of 31ns. I've written more than my share of microcontroller firmwares. But, I feel strongly that he should do as much of the project as he can himself. So, I'll be teaching him some more C, but I'd like that at around the level of GPIB programming and fprintf rather than low-level XMega or other micro-controller programming. So, if there was a way for the 53230A to do this, it sure would have a pretty display that he'd like (and a 20 ps single-shot resolution that I'd like). Yes, I have some thunderbolts that I've used with some Soekris net4501's+nonoBSD and they're great. But, he's keen on using an the PRS-10 for his reference clock. Something about the term atomic, I'm sure. And, since we're just talking milliseconds(!) over a month or so, then the PRS-10 will do well without any GPS disciplining. Kevin ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Looking for off-the-shelf device to timestampmultiple PPS inputs
Hi Bob, That's a fine solution that wins on re-use of old PC's and scalability of inputs. Obviously over the course of days, NTP is superior to an Rb clock, but my son really wants to use the Rb for reference time. I suppose we could read the PPS from the Rb to compare to the other two PPS lines, though. Could be a winner. In fact, if don't use NTP to discipline the local clock, we can use the local clock as a measurement of a the stability of a quartz oscillator for his project. Not having used counters much, I'm a little surprised they can't do continuous logging. I suppose their strengths, though, are in triggering and gating. Kevin Sent from my iPad On Sep 28, 2011, at 3:28 PM, Bob Camp li...@rtty.us wrote: Hi For milliseconds, route the signals into a hard wired parallel port (not USB) and sample the data. Looking at it 1K times a second is pretty easy. All software running on a tired old PC. Sync the thing up with NTP or what ever to keep it stable long term. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Kevin Rosenberg Sent: Wednesday, September 28, 2011 3:56 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Looking for off-the-shelf device to timestampmultiple PPS inputs On Sep 28, 2011, at 1:21 PM, Chris Albertson wrote: Milliseconds? So why are we talking about HP counters and PicTic and so on. A basic low end Linux system that is controlled by NTP and a GPS receiver is maybe about 100X better than your requirements. (I figure you are looking for about 1000 parts per million, NTP is way better then that if you have a local GPS) Heh! I suppose milliseconds don't really belong on time nuts, they're in the range of polling! But, for his needs, that's sufficient resolution. What would be nice is if the PPS times would just show up log file for him. Hence, the request about off-the-shelf hardware. But, as long as I'll be looking at buying some new hardware, I'd be glad to get resolution of nanoseconds or better. Probably best sigma for the price will be the XMega with 32 MHz input from Clockbox with a sigma of 31ns. I've written more than my share of microcontroller firmwares. But, I feel strongly that he should do as much of the project as he can himself. So, I'll be teaching him some more C, but I'd like that at around the level of GPIB programming and fprintf rather than low-level XMega or other micro-controller programming. So, if there was a way for the 53230A to do this, it sure would have a pretty display that he'd like (and a 20 ps single-shot resolution that I'd like). Yes, I have some thunderbolts that I've used with some Soekris net4501's+nonoBSD and they're great. But, he's keen on using an the PRS-10 for his reference clock. Something about the term atomic, I'm sure. And, since we're just talking milliseconds(!) over a month or so, then the PRS-10 will do well without any GPS disciplining. Kevin ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Looking for off-the-shelf device to timestampmultiple PPS inputs
On Wed, Sep 28, 2011 at 4:20 PM, Kevin Rosenberg ke...@rosenberg.net wrote: Hi Bob, That's a fine solution that wins on re-use of old PC's and scalability of inputs. Obviously over the course of days, NTP is superior to an Rb clock, but my son really wants to use the Rb for reference time. I suppose we could read the PPS from the Rb to compare to the other two PPS lines, though. Could be a winner. In fact, if don't use NTP to discipline the local clock, we can use the local clock as a measurement of a the stability of a quartz oscillator for his project. Not having used counters much, I'm a little surprised they can't do continuous logging. I suppose their strengths, though, are in triggering and gating. Counters will not log the time of a pulse but they will continuously measure time intervals.And the interval might be time from the last tick ofthe second. So you 'd use the Rb's PPS to trigger the start channel and the device under test to trigger the stop channel. the counter measures the time difference. You don't care what the difference is but only how it changes over time. If the pulses are going at different rates you will see the times get longer and long and then very short. later you figure out the beat frequency and then you have the rate of the DUT. A Thunderbolt will do as well as Rb. Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Looking for off-the-shelf device to timestampmultiple PPS inputs
On Sep 28, 2011, at 5:46 PM, Chris Albertson wrote: Counters will not log the time of a pulse but they will continuously measure time intervals.And the interval might be time from the last tick ofthe second. So you 'd use the Rb's PPS to trigger the start channel and the device under test to trigger the stop channel. the counter measures the time difference. You don't care what the difference is but only how it changes over time. If the pulses are going at different rates you will see the times get longer and long and then very short. later you figure out the beat frequency and then you have the rate of the DUT. Thanks, Chris, that makes sense. I considered recommending my DTS-2077 using a phase difference method like that. But, one of the goals is to count all PPS cycles, not just the rate of the DUT, especially if one of the oscillators is less stable than expected. A Thunderbolt will do as well as Rb. For timing purposes, sure. In the thread, also talked about the benefits of NTP. Nonetheless, my son wants to use the Rb and (more importantly) understand some of the physics of the Rb. So, while the Rb as a long-term reference isn't as good as NTP +/- Thunderbolt, it intrigues him. That's good enough for me to help him with his goal. Kevin ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
