[time-nuts] question about multi-way measurement

[Jerry Hancock]

The other issue is application priority in windows.  Here’s an example.  I have a timer running at .75 seconds in Visual Basic.  To the left is normal priority and to the right I set the application to real time priority in device manager.

I then calculated the time between timer interrupts.  I was having a problem reading my 3457a over GPIB using Visual basic at a consistent rate.  I still can’t figure out why every 4 or 5 reads, the time increases by about .05 seconds.  It’s not in the 3457a, could be in the Keysight VISA code. What I need is a way to read GPIB with an STM32F7 board.

After setting the priority to real time, the standard deviation improved by a factor of 7.  By the way, I thought it was interesting that my PC counts ticks to .1us.  



Regards,

Jerry


> On Dec 26, 2018, at 3:42 PM, Hal Murray <hmurray at megapathdsl.net> wrote:
> 
> 
> tvb at LeapSecond.com said:
>> But most people have only one counter (one internal or external timebase
>> reference) and one clock to be measured. So the measurements are one-to-one.
>> If you have more references or more clocks, you're welcome to combine 2, or
>> 3, or as many as you want. It gets complicated but in some cases this
>> complexity is justified. 
> 
> Lots of people have several PCs, each with their own clock.  If you have your 
> time-nut hat on, they are crappy clocks with lots of common mode errors 
> (temperature, network delays).  I think the techniques should apply.
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.