[time-nuts] Is Timelab with a Prologix-Eth and a PM6680 - working ?

[cfo]

On Tue, 03 Jul 2012 15:33:33 -0700, John Miles wrote:

>> Ahhh ... Thanx now i know why my 1hr Trace Duration was so fast. I
>> assumed that Timelab would set the sampling interval written in Timelab
>> via GPIB. But i'll just select 1sec manually.
> 
> That can be a bit confusing.  The TimeLab drivers for GPIB counters
> don't attempt to program the counter in any respect, beyond perhaps
> turning off continuous acquisition so that the program can fetch
> readings synchronously. The program may also disable various statistical
> features that are known to interfere with reading a stream of simple TI
> or frequency measurements.  But for the most part, TimeLab expects you
> to configure the counter manually, using whatever settings and
> parameters you want.  Then you have to fill in the acquisition dialog to
> tell the program what you're doing.
> 
> This lazy approach violates the most commonly recommended GPIB
> programming practice, where the program begins by resetting the
> instrument to its default state and then programs all modes and settings
> of interest.  But it's the only way I can afford the time to support
> lots of different counter models, most of which I don't own. :)
> 
> For counters in talk-only mode, the acquisition driver can't program the
> instrument at all, so the above is doubly true.
> 
> In the specific case of the Trace Duration field, TimeLab will estimate
> the rate at which readings arrive from the counter if you press the
> "Monitor" button and wait a bit for the estimate to settle down.  If it
> doesn't seem to be converging on the right rate, try toggling the
> Monitor button off and on.  Otherwise, if you don't use the Monitor
> feature, you will have to enter the trigger rate manually.
>  
>> I will try this now , and i assume i should then select Frequency in
>> the Data Type - In TimeLab , as i don't use A->B measurements .. Or ?
> 
> Most TICs exhibit some dead time between GPIB readings in
> frequency-count mode.  For instance, if you use an HP 5370B in FREQ
> mode, you'll see something like 1.1 seconds between readings, instead of
> the 1-second gate time you may have selected at the counter's front
> panel.  Not the end of the world, but something to keep in mind when
> deciding whether you want to capture TI or frequency data.
> 
> That being said, when I use my 5370B, I usually use frequency mode with
> a 1-second gate time.  It's quicker and much less error-prone to set up.
>  The quantization/jitter floor isn't that much worse than what a TI
> measurement can achieve, I don't have to worry about whether the START
> and STOP sources are stable and close enough in frequency to avoid
> undersampling phase wraps, and the resulting data quality is OK for many
> purposes.   This will be true for most other counters as well.  When you
> are first getting started with TimeLab, I'd recommend sticking with
> frequency readings until you're more familiar with the overall process. 
> Once frequency readings are being collected and displayed properly, you
> can consider switching to TI mode when appropriate.
> 
> Finally, the Prologix adapters should work well with the various GPIB
> counter options in TimeLab, but especially with the Ethernet adapter,
> you may not want to use trigger rates faster than 1 Hz, at least not at
> first. As you get closer to 10 readings per second, the likelihood
> increases that the combination of the Ethernet adapter and the TimeLab
> driver won't keep up.   The firmware in the Ethernet adapter doesn't
> handle these overrun conditions very well, and may lock up hard enough
> to require a power-cycle to recover.  When I use a GPIB-Ethernet dongle
> with my 5370B, I usually keep the display rate control near 12 o'clock
> to limit the trigger rate to 4-5 per second.  That's very reliable in my
> experience, but 10+ readings per second is not.
> 
> -- john, KE5FX
> www.miles.io

Hi John Thanx for a nice program , and the detailed explanation.

Here is a graph of my Tbolt 10Mhz connected to Ext-Ref & Chan-A , on my 
new PM6680. The 10Mhz is distributed via a 350Mhz RGB Video-Dist-amp
A Procon : 4516-01 , same as Solecis: AVB-DA-RGBHV-0106

http://imageshack.us/photo/my-images/405/tbolt8hfreq.png/

The result looks more like what i expected .... 

"The Lady"  shows 5.43E-13 as ADEV on the Tbolt-Osc , so the above might 
be what to expect.


Thanx to all that have contributed to my learning process :-)

CFO - T-Nut Beginner