Agilent/HP 53131A vs. 53132A universal counter resolution?

[rfspezi]

I got the chance to get an Agilent/HP 53131A universal counter (no options, good display) for 340,- USD.
Besides the question if it is a good deal, i would like to know if it is possible to get 12 digits (as the 53132A provides) out of the 53131A aswell if i increase the gate time?
Initially i always looked for the 12 digit 53132A version but if it only takes a longer gate time to get 12 digits on the 53131A aswell, then i guess it's ok?
thanks

[maxwell3e10]

I believe 53131 and 53132 have a similar counting algorithm, but 53132 has a better time resolution. In general, for a simple counter, they are good deal. HP53310A has better performance and can be found for cheaper, but is a bit harder to use.

[DaJMasta]

You can get more digits on any counter with longer gate times, but the benefit of a counter with a smaller timestamp resolution/more digits per second is that you don't have to, so for a given gate time or burst length, you can get a more precise reading.  An 8 digit a second counter can give you 12 digits, accurately, on a very long gate time, but the 12 digit/s counter can give you the same in one second or can give you 8 digits with only a fraction of a second worth of a burst.  This begins to matter more if the source you're measuring drifts around or if it's only present in very short bursts.

[rfspezi]

I believe 53131 and 53132 have a similar counting algorithm, but 53132 has a better time resolution. In general, for a simple counter, they are good deal. HP53310A has better performance and can be found for cheaper, but is a bit harder to use.

The HP53310A looks quite interesting.
I guess devices that are even able to do Allan variance measurement are a lot more expensive and hard to get?

[DaJMasta]

Stuff that will do the measurements internally and display it sure are, but if you can talk to the unit over GPIB or otherwise, a computer application can usually do it quite easily!  I don't remember the name, but I know there's a freeware measurement software that's been linked around here before that supports a number of counters and will make the measurements directly.

The modulation domain analyzer is very powerful for very small fluctuations, but I think the reason they didn't make subsequent models is that regular high performance counters can do this same sort of stuff.  You could consider something like a Fluke/Philips brand counter (they have some good ones), or other brands that can be comparable or a bit cheaper.  Occasionally you can find a Fluke PM6690 or a Tek FCA3000 series counter for a reasonable price, but it's been a bit since I've seen them go for a good price...  another option to monitor would be the 53210a, which is basically a current model, but which is occasionally pretty cheap.  I think SRS has a counter or two that could fit the bill as well, though the brand typically isn't cheap on the used market.

[rfspezi]

I guess you mean one of these tools: Stable32, Timelab, Plotter, Alavar, Allantools
So i will probably go with the HP 53131A.

[DaJMasta]

Timelab was the one I was thinking of, you can probably check automatic compatibility, but I suspect any counter that can measure remotely can feed the right values into the software.

[Dr. Frank]

 If you want 12 digit resolution, or to be more precise 10^-12(what's your application,  anyhow?), that's not easily done with any counter in 1sec.
The internal time interpolation method usually determines the 1sec resolution, so this should be 100ps or 10^-10/sec for the '132, but 500ps or 5*10^-10 only for the '131.
Both counters use sort of running average, which virtually  increases the resolution/sec.
12digits/sec I think is not a reasonable specification.

Somewhere on time-nuts, it's described that this mechanism falsifies somehow the allan distribution statistics, and if you want to calibrate or compare e.g. a Rb vs. GPSDO, you should use different methods than frequency measurement, to achieve real 10^-12  resolution/accuracy.

This method would better be a phase detection, or T.I. measurement between both sources, accumulated over a longer period of time, like 1000...10000sec, using TimeLab or similar.
For that purpose, even 1ns is enough resolution, but 100ps would give faster results.

Btw. the old 5370B has 20ps T.I. resolution and yields real 12 digits or 10^-11 in one sec.
Frank

[maxwell3e10]

The two approaches, internal interpolation and back-to-back counting, are not mutually exclusive. As the data in the 53310A counter tread show, one can have both 1/tau Allan deviation and enhanced resolution at the same time.
It only messes up Allan deviation for very short times, because two successive measurements are not independent.
Internal interpolation simply means that one measures not just the first and last zero crossings of the signal, but a bunch of zero crossings. It helps to average down both the noise in the counter and the noise in the signal. Otherwise, one is throwing away 10 million zero crossings just to measure two of them.

[5065AGuru]

The 53131A will talk only to an RS232 Logger.
I have done DMTD (Dual Mixer Time Difference) plots using my 53131A in Time Interval mode and HyperTerminal in my laptop.
Some of the other programs mentioned can be used to take the data also.
You can also use a Single mixer system and period mode.
This is handy as it eliminates any phase wraps!

Cheers,

Corby

[FriedLogic]

The two approaches, internal interpolation and back-to-back counting, are not mutually exclusive. As the data in the 53310A counter tread show, one can have both 1/tau Allan deviation and enhanced resolution at the same time.
It only messes up Allan deviation for very short times, because two successive measurements are not independent.
Internal interpolation simply means that one measures not just the first and last zero crossings of the signal, but a bunch of zero crossings. It helps to average down both the noise in the counter and the noise in the signal. Otherwise, one is throwing away 10 million zero crossings just to measure two of them.

Although it can be very useful to use a lot of crossings for measuring frequency, it's a problem when trying to measure stability. It effectively filters the data, and has a different effect with different noise types, so the end result is a bit different from 'normal' Allan deviation.

[ArthurDent]

I have a nice HP 53132A eBay special with opt10 and opt30 with a pretty bright display and I do like the 12 digit/second display. I also have a Pendulum CNT-81 (Fluke/Philips PM6681) and use it to check 10Mhz frequency standards. Using the math function to subtract 9,999,999Hz and with a 10 second time base, it will display 1.00000Hz if the external reference and the input are the same frequency.  This is actually 10,000,000.00000Hz but I probably have more resolution than accuracy.