Thanks Chuck,

I found FEBO has an article on the 5370B here
http://www.febo.com/time-freq/hardware/5370B/index.html

As a footnote, my 5335A is rock stable sitting on 10 Mhz all day.

Best regards,
Mark

Mark,

The 5335 is specified at 9 digits/second of resolution, the 5370 is
specified at 12 digits/second.

That's 3 orders of magnitude better resolution. That brings up noise that at
9d/s is simply negligible.

My two 5370s are rock stable if I only look at the 9 left-most digits.

While it would be nice to have the same stability at 12d/s on the 5370 as we
get on the 5335 at 9d/s, that simply does not happen.

Didier KO4BB

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From: "Didier Juges" didier@cox.net
Subject: Re: [time-nuts] HP 5370B
Date: Fri, 9 May 2008 20:11:42 -0500
Message-ID: 005001c8b23a$cf4e6d90$0a01a8c0@didierhp

That is severly overoptimistic on the 5370's part and just about overoptimistic
on the 5335's part. I think you should not use those sales-numbers, as they are
there to give you a one-figure-of-merit hint, but they are not qualitative
values.

I'd suspect something like 40 times better, not 1000 times better.
The 5335 singel-shot resolution is 500 ps while the 5370 has 25 ps, a factor of
20. The front-ends is not that good on the 5335 thought, so let's add some
noise there.

I could make some tests if you like...

Maybe you should trim your multiplier chain?

I don't see how you could expect that. 10 digits stable should be possible, but
again it is just a very very rought estimate of performance.

Cheers,
Magnus

Magnus Danielson wrote:

Actually the 5370 single shot resolution is 20ps, however the noise is a
little larger than that.
It can be much larger if the input signal slew rate at the trigger point
is much less than about 7.5V/us (input attenuation = 1X).
The performance also deteriorates when the input amplifiers are severely
overdriven.
Since the 5370 input amplifier noise bandwidth is 500MHz the wideband
noise seen by the 5370 inputs should also be low.

Aligning the various filters in the 10MHz to 200MHz multiplier chain can
make a considerable difference to the apparent noise.

Bruce

Sorry if my answer was confusing. I did not mean to imply that the 5370 was
3 orders of magnitude more accurate than the 5335, simply that it attempts
to display data with 3 orders of magnitude greater resolution (3 orders of
magnitude more precise). The 5370 spec indicates 20 pS accuracy in
single-shot TI measurements, while it displays the data with 1 pS
resolution. In that mode, even with ideal signals coming in, there is
significant jitter on the displayed value.

That's a good illustration of the difference between precision and accuracy.

I think it shows where the limits of conventional technology lies. There are
a lot of 9 d/s counters, and most of those I have seen are perfectly stable
at that level. Some are even very simple and inexpensive. To get
significantly better requires exponentially more difficult technology, at
least considering what was available 20 years ago.

Didier KO4BB

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This is not unique to the 5370 counter. Many instruments have precision that
far exceeds their accuracy. Most microwave network analyzers have amplitude
resolution of 0.01dB, while their accuracy is just around 1dB in most cases.

There are a few cases where it can actually be useful, but in the vast
majority of cases, it simply confuses the hell out of the unsuspecting QA
person.

I have had to argue too many times that a piece of equipment with a 2dB p-p
requirement on flatness was just fine when it measured 2.01dB on the HP
network analyzer. I would not have gotten in that argument if the data had
been 1.99dB. Go figure.

Didier

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At 09:22 AM 5/10/2008, Didier Juges wrote...

I figure you're both wrong. If the measuring instrument is no better
than 1 dB absolute, you can't expect to do it - a flat line measurement
could represent an actual + or - 1 db, the limit of the spec.

I knew would get comments on that. I simply did not provide enough
information. I thought most everyone who has done it would know what I was
refering to.

Acuracy of these instruments is not one number, it is a 3 dimensional chart,
and time is the 4th dimension.

Forget I even mentioned it. I do not intend to go into an error analysis
now.

Didier

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Of course, actually that was the point of my posting.

Most people assume that what they read on the instrument's display is the
truth. As long as they read on the proper side of the requirement, (less
than a max, or more than a min) all is good.

I have been in this business for 30 years. They all do it, Raytheon,
Lockheed-Martin, Boeing, Northrop-Grumman, just to cite the better known.

The truth is usually a little more complicated than that.

Didier

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On May 10, 2008, at 15:07, Didier Juges wrote:

In my view precision and accuracy have the same meaning and here is a
mix up between accuracy and resolution.
The 5370 has a resolution of 1ps but the accuracy is much lower. Say
the 20ps stated above.
Thus, in my view,  there is no difference between precision and
accuracy, but between accuracy and resolution there is.

Henk

Henk ten Pierick said the following on 05/10/2008 12:30 PM:

There's a confusing set of definitions between accuracy, resolution, and
precision.

The 5370 makes it even more complicated because its actual resolution is
20ps (single shot) while the display can look more like 1 ps (if you
plot the data you'll see discrete 20ps granularity).  From the
experiments I've done, after you factor in trigger error and other
uncertainties, the 5370 usable accuracy is about 60ps single shot.

John

In message 27DF566C-9F20-4C0B-A740-22538A826D03@deriesp.demon.nl, Henk ten Pi
erick writes:

And just to make it maddenign difficult, it's not actually 20ps,
it is:

19.53125 ps [5ns/256]

or possibly

19.60783137... ps [5ns/255]

...I can never remember which.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

At 10:43 AM 5/10/2008, Didier Juges wrote...
(corrected for top-posting)

Exactly what (real world, not something made up to match the claim like
-.02 to -1.00) accuracy spec allows a reading of 2.01 to meet a spec of
max 2? Please tell us what you're referring to. I don't claim to be an
expert at math or statistics, but I just don't see it.

I understand that there is the possibility that the DUT is in spec
due to measurement uncertainty, but to say it's "just fine" (i.e.
guaranteed to  be within spec) can't be claimed. Aren't you measuring
so you can guarantee the spec is met? If you say 2.01 is as acceptable
as 1.99, then what about 2.02? 2.03?...999.00?

You seem to be trying to make the point that a measurement difference
of .02 is meaningless if the accuracy is some amount greater than that.
That's a losing argument, since there has to be some defined point
beyond which the spec can't be guaranteed. For your example, it might
be impossible except for a perfect measurement, as in the example I
gave. In any case, the measurement would always have to be less than
the specification. How much less would depend on the accuracy. Maybe
it's 1.50, maybe it's 1.49, but it's a pass/fail test, either the
specification is guaranteed by the measurement, or it isn't (excepting
statistical specs).

Henk ten Pierick wrote:

Henk,

I disagree with your definitions.

Resolution addresses the smallest increment that can be discerned.

Precision addresses how well one is able to make repeated measurements to the
provided resolution.

Accuracy addresses how well a measurement coincides with an acceptably understood
and agreed upon reference.

Bill....WB6BNQ

From: Bruce Griffiths bruce.griffiths@xtra.co.nz
Subject: Re: [time-nuts] HP 5370B
Date: Sun, 11 May 2008 00:15:34 +1200
Message-ID: 482591E6.4070806@xtra.co.nz

Thanks for correcting that. My memory failed me there...

Trigger jitter always adds, but single shot resolution limits the "digits
per second" fairly well.

Indeed.

Cheers,
Magnus

From: "Didier Juges" didier@cox.net
Subject: Re: [time-nuts] HP 5370B
Date: Sat, 10 May 2008 08:07:38 -0500
Message-ID: 007f01c8b29e$d337b740$0a01a8c0@didierhp

Didier,

You must recall that the 5370 is not a pure multiple of 1, 2 or 5 ps and this
requires additional digits for propper decimal representation.

Tossing up as much as 12 digits for a 1 s measurement while having about 20 ps
of resolution does not give 12 digits per second.

I think you need to go even longer back in time for the 5370.

Advances have been made and 200 fs resolution have been manufactured. However,
those are ill suited for "normal" TI and frequency counter applications.

Achieving true 12 digits/s performance is possible but a bit challanging.

Cheers,
Magnus

From: "Poul-Henning Kamp" phk@phk.freebsd.dk
Subject: Re: [time-nuts] HP 5370B
Date: Sat, 10 May 2008 17:16:02 +0000
Message-ID: 9243.1210439762@critter.freebsd.dk

You are correct. It's 5 ns / 256. The 20 ps is a handy rought estimate.
It is best viewed as being counted in a 51,2 GHz counting clock.

And to comment on the resolution/accuracy aspectt... they are certainly not the
same.

The resolution is what every steps the hardware will divide the time in.

The precission of those samples can deviate alot, and cross-talk will shift the
time. Biases wiil also show up in TI measures. A calibrator is needed to cancel
those.

The accuracy of the measure also includes the trigger jitter aspect.

Thus, the achieved accuracy and precission is certainly a combined effect of
many error sources. Viewing the shown digit as equalent to the provided
resolution is at best naive. True for some instruments, but not for others.
When in doubt, read the manual.

Cheers,
Magnus

The point is that in my 30 years experience is selling equipment to
government and prime contractors, I have never had a piece of equipment
rejected because a reading was 1.99 for a spec of 2 max, but I have seen
many cases where an instrument reading 2.01 (or, God forbid 2.001 dB as some
can display) being argued as being unacceptable. We all know that a reading
1.99 does not guaranty that the equipment is actually better than 2, but I
have never had to make that argument.

I am not saying that a reading 2.001 is always acceptable when the spec says
2 max, but in most cases, make the same reading again a while later and
chances are good that you will be under 2 (or maybe way out).

If you read 2.01 for a spec of 2 max and the instrument is 1% acurate, you
have not established that the equipment was out of spec because the reading
could be off by 0.02. Now, there are other standards and practices. If you
specify a parameter to be 2 max for instance, it is not the same as 2.0 max.
The accepted practice is to round to the required significant digit, so that
if the spec is 2 max, a reading of 2.4 would be rounded to 2 and be
acceptable, but it would not be acceptable if the spec was 2.0 max. Not all
customers interpret it that way, but most do.

Please note that these problems are more pronounced with microwave signals
than with things that are more easily measured, such as DC voltage. In the
microwave world, It is always extremely frustrating to try and correlate the
accuracy claims. You can take two instruments that are both 1% accurate and
with calibration tracable to NIST, and yet they will be off by several %
from each other. This is routine. There are simply too many factors
involved, such as VSWR, connector problems and so on.

Didier

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At 04:07 PM 5/10/2008, Didier Juges wrote...

My mistake. If I ever used a measurement beyond it's accuracy to
fraudulently claim compliance with customer specification, I'd quickly
lose customers. Your business must be different.