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Discussion of precise time and frequency measurement

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5370 processor boards available

MD
Magnus Danielson
Sat, Mar 1, 2014 10:32 AM

On 28/02/14 18:42, Tom Van Baak wrote:

I think one of the best chances would be to improve the phase
noise of the 200MHz signal.

But don't miss the fact that being able to make a LOT more measurements
in the same time also improves noise statistically.

I agree with this. And it makes me wonder if someone on the list is now eyeing the SR 620 as the next classic instrument in need of a time nuts upgrade?

It would be very cool if in the end both the hp5370 and the SR620 can be turned into true timestamping counters, a la the Pendulum CNT-9x and the Agilent 53230.

Indeed.
Just having ethernet and USB on them would help a lot.

The key point is that you need to hide the dead-time between the stop
trigger and the arm trigger. You also need continuous time to be
assuered, which typically means a runnning time counter. None of them is
made to be a zero dead-time counter, where as HP-5371/5372/5373 and
CNT-9x is. I think one has to think a little about how the counter HW is
being extended to achieve the true ZDT properties.

The typical way for getting these counters hide their dead-time have
been a higher rate trigger signal than arm signal (typcially x2). The
other way is to use a pair of counters and having them being armed on
every other measure.

Cheers,
Magnus

On 28/02/14 18:42, Tom Van Baak wrote: >> I think one of the best chances would be to improve the phase >> noise of the 200MHz signal. >> >> But don't miss the fact that being able to make a LOT more measurements >> in the same time also improves noise statistically. > > I agree with this. And it makes me wonder if someone on the list is now eyeing the SR 620 as the next classic instrument in need of a time nuts upgrade? > > It would be very cool if in the end both the hp5370 and the SR620 can be turned into true timestamping counters, a la the Pendulum CNT-9x and the Agilent 53230. Indeed. Just having ethernet and USB on them would help a lot. The key point is that you need to hide the dead-time between the stop trigger and the arm trigger. You also need continuous time to be assuered, which typically means a runnning time counter. None of them is made to be a zero dead-time counter, where as HP-5371/5372/5373 and CNT-9x is. I think one has to think a little about how the counter HW is being extended to achieve the true ZDT properties. The typical way for getting these counters hide their dead-time have been a higher rate trigger signal than arm signal (typcially x2). The other way is to use a pair of counters and having them being armed on every other measure. Cheers, Magnus
MD
Magnus Danielson
Sat, Mar 1, 2014 10:35 AM

On 01/03/14 11:31, Poul-Henning Kamp wrote:

In message 5311B3EB.1000409@rubidium.dyndns.org, Magnus Danielson writes:

What one possibly could do is to see if there is any round-off issues
that causes any noise.

The HP5370 firmware uses floating point to avoid exactly that issue,
and all the math I've traced is good and competent.

OK. Good.

I've seen it with others. In fact, I learned about the issue when seeing
data from Pendelum as they where a little confused about it.

Cheers,
Magnus

On 01/03/14 11:31, Poul-Henning Kamp wrote: > In message <5311B3EB.1000409@rubidium.dyndns.org>, Magnus Danielson writes: > >> What one possibly could do is to see if there is any round-off issues >> that causes any noise. > > The HP5370 firmware uses floating point to avoid exactly that issue, > and all the math I've traced is good and competent. OK. Good. I've seen it with others. In fact, I learned about the issue when seeing data from Pendelum as they where a little confused about it. Cheers, Magnus