[time-nuts] TimeLab

Sun Oct 9 12:49:48 EDT 2016

FWIW, I have only tried timelab reading a live ascii log file.

On Sunday, 9 October 2016, Magnus Danielson <magnus at rubidium.dyndns.org>
wrote:

> Which removes the real-time processing benefit of using TimeLab in the
> first place.
>
> What I propose is not too complex to do.
>
> Cheers,
> Magnus
>
> On 10/09/2016 06:19 PM, Bob Stewart wrote:
>
>> Don't forget the possibility of saving the data to a file and
>> pre-processing the file before sending it to Timelab.
>> Bob
>>  -----------------------------------------------------------------
>> AE6RV.com
>>
>> GFS GPSDO list:
>> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>>
>>       From: Magnus Danielson <magnus at rubidium.dyndns.org>
>>  To: time-nuts at febo.com
>> Cc: magnus at rubidium.se
>>  Sent: Sunday, October 9, 2016 10:48 AM
>>  Subject: Re: [time-nuts] TimeLab
>>
>> Hi,
>>
>> Well, yes. You can do some fancy stuff with additional hardware, but I
>> think with already a handful of relatively simple software fixes and
>> some basic setup conditions, a sufficiently robust method emerges.
>>
>> I could not sign-swap the measurements in TimeLab when I tried.
>> I don't seem to be able to force the unwrapped phase to be +/- half cycle.
>> I don't seem to be able to offset my readings. I have two sources of
>> offset, one is the additional delay of cables, and the other is the
>> offset due to wrong cycle (I hope this one can be baked into alternative
>> phase-unwrapping mode). I would prefer if I could hit calibration to
>> establish the zero-level. Typically I use a BNC barrel and well, it does
>> add smoe more delay
>>
>> What I propose should be doable with a simple counter like 5335A,
>> 53131/2A or similar. If you have a locked say 100 Hz or 1 kHz signal
>> (TADD-2 can be useful if the GPSDO does not output proper signal), you
>> can do the picket fence and resolve things, it is just that there is a
>> few things to aid in the post-processing to make values useful.
>>
>> I further hint about a few things which makes easier to analyze is the
>> improved support for zooming.
>>
>> Oh, I do care about phase variations and absolute phase measures. I do
>> such measures a lot. ADEV and TDEV is not all the things I measure,
>> especially when considering systematic effects.
>>
>> Cheers,
>> Magnus
>>
>> On 10/09/2016 03:42 PM, Bob Camp wrote:
>>
>>> Hi
>>>
>>> Given that *some* of us have more than errr … one counter :)
>>>
>>> There are several setups that involve two or three counters to resolve
>>> some of these issues. Having
>>> multiple serial ports or multiple devices on a GPIB isn’t that big a
>>> problem. Addressing multiple devices
>>> (setting up the addresses in TimeLab) is an added step. Coming up with
>>> standard setups would be the
>>> first step. Getting them documented to the degree that they could be run
>>> without a lot of hassle would be
>>> the next step.
>>>
>>> Another fairly simple addition (rather than a full blown counter) would
>>> be some sort of MCU to time tag
>>> the input(s). It’s a function that is well within the capabilities of a
>>> multitude of cheap demo cards. Rather than
>>> defining a specific card, it is probably better to just define a
>>> standard message (115200 K baud, 8N1, starts
>>> with “$timenuts$,1,”, next is the channel number, after that the (32
>>> bit?) seconds count.The final data field is
>>> a time in nanoseconds within the second, *two byte check sum is last,
>>> cr/lf). If there is a next generation version that is
>>> incompatible, the 1 after timeouts changes to a 2.) Yes, even 10 seconds
>>> after typing that definition I can see
>>> a few problems with it. Any structural similarity to NMEA is purely
>>> intentional. That’s why it needs a bit of
>>> thought and work before you standardize on it. It still would be a cheap
>>> solution and maybe easier to integrate
>>> into the software than multiple counters. You do indeed have all the
>>> same setup and documentation issues.
>>>
>>> In any of the above cases, the only intent of the added hardware is to
>>> get a number that is good to 10’s of ns.
>>> Anything past that is great. Once you know where all the edges really
>>> are, sorting out the phase data becomes
>>> much easier.
>>>
>>> Bob
>>>
>>> On Oct 9, 2016, at 7:32 AM, Magnus Danielson <magnus at rubidium.dyndns.org>
>>>> wrote:
>>>>
>>>> Fellow time-nuts,
>>>>
>>>> I don't know if it is me who is lazy to not figure TimeLab out better
>>>> or if it is room for improvements. I was considering writing this directly
>>>> to John, but I gather that it might be of general concern for many, so I
>>>> thought it be a good topic for the list.
>>>>
>>>> In one setup I have, I need to measure the offset of the PPS as I upset
>>>> the system under test. The counter I'm using is a HP53131A, and I use the
>>>> time-interval measure. I have a reference GPS (several actually) which can
>>>> output PPS, 10 MHz, IRIG-B004 etc. In itself nothing strange.
>>>>
>>>> In the ideal world of things, I would hook the DUT PPS to the Start
>>>> (Ch1) and the reference PPS to the Stop (Ch2) channels. This would give me
>>>> the propper Time Error (DUT - Ref) so a positive number tells me the DUT is
>>>> ahead of the reference and a negative number tells me that the DUT is
>>>> behind the reference.
>>>>
>>>> Now, as I do that, depending on their relative timing I might skip
>>>> samples, since the counter expects trigger conditions. While TimeLab can
>>>> correct for the period offset, it can't reproduce missed samples.
>>>> I always get suspicious when the time in the program and the time in
>>>> real world does not match up.
>>>>
>>>> I could intentionally shift the PPS output of my DUT to any suitable
>>>> number, which would be one way to solve this, if I would tell TimeLab to
>>>> withdraw say 100 ms. I might want to do that easily afterhand rather than
>>>> in the setup window.
>>>>
>>>> To overcome this, I use the IRIG-B004 output, which is a 100 Hz signal
>>>> with a stable rising edge aligned to the PPS to within about 2 ns. Good
>>>> enough for my purpose. However, for the trigger to only produce meaningful
>>>> results, I will need to swap inputs, so that the PPS from DUT is on
>>>> Start/Ch1 and the IRIG-B is on Stop/Ch2. This way I get my triggers right.
>>>> However, my readings have opposite sign. I might have forgotten about the
>>>> way to correct for it.
>>>>
>>>> However, TimeLab seems unable to unwrap the phase properly, so if I
>>>> have the condition where I would get a negative value of say -100 ns then
>>>> the counter will measure 9,999,900 ns, so I have to force a positive value
>>>> as I start the measurement and then have it trace into the negative. I
>>>> would very much like to see that TimeLab would phase-unwrap into +/-
>>>> period/2 from first sample. That would be much more useful.
>>>>
>>>> I would also like to have the ability to set an offset from which the
>>>> current zoom window use as 0, really a form variant of the 0-base but
>>>> letting me either set the value or it be the first value of the zoom. I
>>>> have use for both of these. I often find myself fighting the offset issues.
>>>> In a similar fashion, I have been unable to change the vertical zoom, if I
>>>> don't care about clipping the signal then it forces me to zoom in further
>>>> than I like to. The autoscale fights me many times in a fashion I don't
>>>> like.
>>>>
>>>> OK, so there is a brain-dump of the last couple of weeks on and off
>>>> measurement experiences. While a few things might be fixed in the usage, I
>>>> wonder if there is not room for improvements in the tool. I thought it
>>>> better to describe what I do and why, so that the context is given.
>>>>
>>>> Cheers,
>>>> Magnus
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>>>
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