[time-nuts] HP 5372A vs. 5370A

[Magnus Danielson]

On 09/02/11 22:14, Ed Palmer wrote:
> I routinely use the 5372A to make multiple 1 sec. measurements of
> frequency or time interval and then dump the results via GPIB for
> analysis. Standard stuff for either the 5370 or 5372 except as mentioned
> elsewhere, these measurements are made with no dead time.

I love the time deviation view.

> My unit has Option 040 which adds FFT capabilities. I can do phase noise
> measurements within the limitations of the 200ps resolution of the box.

Very nifty thing to have in the box. Both the units I use have Option 
040, but I rarely use it.

> The June 2008 issue of Circuit Cellar had an article ("Let's be Crystal
> Clear") on crystals and oscillators. The 5372A was used to analyze the
> startup behaviour of an oscillator. You should be able to get this
> article through inter-library loan or maybe there's a copy lurking on
> the net somewhere. There are also various manuals and app notes online
> at the Agilent site.

The Frequency vs. Time view is lovely.

The 5372A does calculate ADEV but does not provide ADEV plots.

> The biggest limitation of the 5372A is that you can only make 8191
> frequency measurements or 4095 time interval measurements with each
> measurement lasting no longer than 8 seconds. If you want to use it for
> making more or longer measurements (e.g. long term Allan Deviation
> measurements) you have to start doing some GPIB programming, but I think
> you lose the no-dead-time advantage.

The internal memory can handle 8192 time-stamps. Depending on intricate 
details of various measurement modes one or more reference samples is 
taken, and one or two channels is time-stamped. The event and time 
counters is sampled on each measurement but runs continuously, even when 
measurements is not running. You can program bursts such that retrieving 
the burst can be done such that a new burst can be started without 
loosing either the continuous sample series or no-dead-time advantages. 
However you need to do binary transfers.

Another approach is to use the Fast Port which taps into the hardware 
and would allow longer runs. I have not much documentation on it and 
experience on how it works. Needs to play with it.

> If you see a 5372A that's reporting an "Error 160: Out of sensitivity
> cal." don't worry about it. It just means that the onboard lithium
> battery is dead and needs to be replaced. The calibration is trivial to do.

I've done the exercise for two 5372A's and it was easy to do.

> The most important thing about either the 5370 or 5372 is to study it.
> Figure out it's capabilities, limitations, and tricks so that you use it
> to it's full potential. I'm still working on that!

The HP5372A programmers manual is really an inside-out manual where you 
learn the internal formats and how they are processed for the various 
views and results. Very open in what it does and how you can duplicate 
the measurements from binary format. It's a bit confusing initially, but 
once you spent the time to learn it, it makes sense.

There are a few GUI-hacks I would like to have, for longer measurements 
I would like to have an ETA count-down, but real-time update for certain 
views would be lovely. The CNT-90 outshines the HP5372A in this respect. 
The post-measurement zoom functionality of the HP5372A is not a marvel 
of functionality but provides a basic function, where as the CNT-90 
could do more of that.

Cheers.
Magnus