[time-nuts] Looking for off-the-shelf device to timestampmultiple PPS inputs

Kevin Rosenberg kevin at rosenberg.net
Wed Sep 28 23:20:01 UTC 2011


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" <lists at 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-bounces at febo.com [mailto:time-nuts-bounces at 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
> 
> 
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