Hi
> On Oct 9, 2016, at 1:22 PM, Magnus Danielson <mag...@rubidium.dyndns.org> > wrote: > > Hi Bob and Bob, > > This is why the two-counter setup is so messy, you have to have software that > will sync up and query them alternatively. You also need to make sure you get > the counters to trigger. Besides, another issue is that difference in the two > counters read-outs will cause a false signal, so calibration and compensation > becomes important to remove that. That’s why I believe the time tagger + counter is the better solution rather than multiple counters. Let it give you the global information and then use it to sort out what you see from the counter. Yes, a full blown multi channel time tagger with picosecond resolution would be better still. That’s going to cost more than $5…. Bob > > Using a picket fence type of triggering approach is cheaper and easier to > maintain. Some mild software support for the processing and it will work like > a charm. Calibration for true zero offset is needed, but relatively easy to > implement, you want that anyway. > > Cheers, > Magnus > > On 10/09/2016 07:02 PM, Bob Stewart wrote: >> Hi Bob, >> I had actually thought about making a server for the Prologix Ethernet >> adapters, but I gave up when I considered the issue of two processes trying >> to claim the same device. I've experimented with using a C program to >> capture multiple GPIB ports to a live file. But, I can't figure out how to >> get the "live" part to work when running Timelab on a Windows client in a >> Virtual Box under a Linux server that is collecting the data. I think Santa >> may have to bring me another GPIB adapter this Christmas. >> >> Bob >> ----------------------------------------------------------------- >> AE6RV.com >> >> GFS GPSDO list: >> groups.yahoo.com/neo/groups/GFS-GPSDOs/info >> >> From: Bob Camp <kb...@n1k.org> >> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency >> measurement <time-nuts@febo.com> >> Sent: Sunday, October 9, 2016 11:50 AM >> Subject: Re: [time-nuts] TimeLab >> >> Hi >> >>> On Oct 9, 2016, at 12:27 PM, Bob Stewart <b...@evoria.net> wrote: >>> >>> Hi Bob, >>> Is it actually possible to address two devices on one GPIB adapter with >>> Timelab? I admit to not reading the documentation carefully, but I've not >>> been able to do this directly. The only way I could think of doing it was >>> to use some software to send the data to a file and then use Timelab to >>> pull the data from the file. Maybe NI software allows you to configure >>> this? >> >> That was my poorly stated point :) … you would have to add the ability to >> identify and address multiple devices. >> >> Bob >> >>> >>> Bob >>> ----------------------------------------------------------------- >>> AE6RV.com >>> >>> GFS GPSDO list: >>> groups.yahoo.com/neo/groups/GFS-GPSDOs/info >>> >>> From: Bob Camp <kb...@n1k.org> >>> To: Discussion of precise time and frequency measurement >>> <time-nuts@febo.com> >>> Sent: Sunday, October 9, 2016 8:42 AM >>> Subject: Re: [time-nuts] TimeLab >>> >>> 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 <mag...@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 >>>> _______________________________________________ >>>> time-nuts mailing list -- time-nuts@febo.com >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
