Re: [time-nuts] DDS, OCXO and ADEV
The counter is in TIME MODE. And simple calculation could transform it to frequency as necessary. For example: 1/(350.50824*10^-9) 2852999.97512184021693755330 OR 1/0.00350508240900 2852999.96779619226350692058 Which is pretty close to my DDS VFO freq. value [2853000] I switch counter to TIME MODE, because ADEV1 utility using times, not frequency: Here is from documentation: Adev1 works on everything from pendulum clocks to hydrogen masers. The only restrictions are that the data must be phase (time interval) rather than frequency; the data must be sequential (no gaps); and the data should be free from glitches or outliers. I am using 10 second intervals for the measurement. DDS VFO clocked by Trimble TB and its using AD9852 chip. Regards, V.P. On 2015-05-03 10:01, Bob Camp wrote: Hi Either the output data is with the counter set to time mode (and it’s in 100’s of ns) or you have it set to frequency mode and have a very stable system. Bob On May 2, 2015, at 9:53 PM, d0ct0r t...@patoka.org wrote: Hello, I would like to create some charts for ADEV for following setup: HP5386A counter connected to External REF. (OCXO). The input of counter connected to my DDS VFO. The frequency on VFO is 2853000 Hz. Here is what I got from counter via GPIB: S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082409E-7 S +3.505082408E-7 S +3.505082409E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 I converted it to following form: 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240800 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 Then I tried to use ADEV by tvb (long life to Tom!). See attached file 1b.bmp And I tried to create the charts for the collected data. See attached file 1a.bmp. But it seems I am doing something wrong. Any advises will be greatly appreciated. Thanks ! -- WBW, V.P.1a.png1b.png___ 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. -- WBW, V.P. ___ 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.
Re: [time-nuts] DDS, OCXO and ADEV
Hi Either the output data is with the counter set to time mode (and it’s in 100’s of ns) or you have it set to frequency mode and have a very stable system. Bob On May 2, 2015, at 9:53 PM, d0ct0r t...@patoka.org wrote: Hello, I would like to create some charts for ADEV for following setup: HP5386A counter connected to External REF. (OCXO). The input of counter connected to my DDS VFO. The frequency on VFO is 2853000 Hz. Here is what I got from counter via GPIB: S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082409E-7 S +3.505082408E-7 S +3.505082409E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 I converted it to following form: 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240800 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 Then I tried to use ADEV by tvb (long life to Tom!). See attached file 1b.bmp And I tried to create the charts for the collected data. See attached file 1a.bmp. But it seems I am doing something wrong. Any advises will be greatly appreciated. Thanks ! -- WBW, V.P.1a.png1b.png___ 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.
Re: [time-nuts] DDS, OCXO and ADEV
Hi Vlad, Here are some comments. Please read carefully. Look at your data and notice that every reading is the same 3.505082408E-7, except one is 3.505082409E-7. That's not going to give you very good plots at all. Also you're not going to get much information out an ADEV tool with just 13 points. It's not clear from your post what those readings are. They do not look like phase difference. They do not look like frequency, or frequency offset, or fractional frequency error. Instead I will guess they are period, since 1 / 3.505082408E-7 is 2852999.968 and that is close to the frequency you mentioned: 2853000 Hz. My ADEV tools do not accept period or frequency data as input. This is by design. They expect a series of phase measurements. That is, a periodic sampling of the phase difference between the REF and the DUT. There is no need to convert a number like 3.505082408E-7 to a number like 0.00350508240900. Software knows how to read floating point numbers. You can convert your period measurements (seconds) to frequency (Hz) by inverting them. Some tools will then take this frequency data as input. You can convert period measurements (seconds) to fractional frequency error by inverting, subtracting 2853000 Hz, and dividing by 2853000 Hz. Some tools will take fractional frequency error as input. Or, you can convert your period measurements to phase difference by subtracting 1/2853000 and accumulating (running sum) the phase error for each sample. There's a tool for you that does this, p2t, and the arguments are the nominal phase and the sample rate ( www.leapsecond.com/tools/ ). In other words, you can get correct ADEV statistics from your gpib.dat file using: sed gpib.dat s/...// | p2t 1/2853000 10 | adev1 10 I won't get into zero dead time measurements yet. One step at a time. I'm not sure if my tools are the best for you. Command line tools work best when you understand what's going on and can keep track of units and such. Instead consider using John's TimeLab ( www.ke5fx.com/timelab/readme.htm ) which is a GUI with an extensive help system. Your DDS vs OCXO plot looks suspect. You must remove that huge outlier point before you do any statistical analysis (like ADEV). The y-axis of that plot doesn't look right: all the grid lines are zero. Also there are no units. The Allan Variance Plot Y you included is odd. I would not expect a y-axis scale to go from -31 to -45. But this is probably a side-effect of your feeding period readings into an ADEV tool instead of a phase difference time series. If you want send me the full raw data file (more than 13 points), I'll make a set of plots that you can compare against. /tvb - Original Message - From: d0ct0r t...@patoka.org To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, May 02, 2015 6:53 PM Subject: [time-nuts] DDS, OCXO and ADEV Hello, I would like to create some charts for ADEV for following setup: HP5386A counter connected to External REF. (OCXO). The input of counter connected to my DDS VFO. The frequency on VFO is 2853000 Hz. Here is what I got from counter via GPIB: S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082409E-7 S +3.505082408E-7 S +3.505082409E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 I converted it to following form: 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240800 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 Then I tried to use ADEV by tvb (long life to Tom!). See attached file 1b.bmp And I tried to create the charts for the collected data. See attached file 1a.bmp. But it seems I am doing something wrong. Any advises will be greatly appreciated. Thanks ! -- WBW, V.P. ___ 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.
Re: [time-nuts] DDS, OCXO and ADEV
I switch counter to TIME MODE, because ADEV1 utility using times, not frequency: No. ADEV1 expects phase. Not time, not period, not frequency. Here is from documentation: Adev1 works on everything from pendulum clocks to hydrogen masers. The only restrictions are that the data must be phase (time interval) rather than frequency; the data must be sequential (no gaps); and the data should be free from glitches or outliers. Busted! It looks like you broke all three rules: your data was period (not phase), your data has deadtime (gaps), and your data has glitches! Anyway, here is a more complete explanation. The word phase is confusing because it is used differently in time frequency metrology than in other branches of science. The units are seconds (not degrees, not radians, not rotations, not angles). Think of phase as simply the difference between the time that two clocks display. If you call one clock the reference and assume it is the true time, then phase is simply the time error of the DUT clock. Think of a wall clock; maybe 2 seconds behind, or 15 seconds ahead. This is the phase. It tends to wander slowly and grow larger over time. If you were to write down the time error of your clock once a day for a month you'd have a nice set of phase numbers that you can feed to any tool that computes ADEV. Note also that phase is a cumulative measurement. That is, every successive data point reflects the net clock error since you started collecting data. Even if you lost 29 days of data in the middle, you'd still know how far off the clock had drifted in time between day 1 and day 30. If this all makes sense so far, I'll go on to explain how period or frequency measurements are related to this. /tvb ___ 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] DDS, OCXO and ADEV
Hello, I would like to create some charts for ADEV for following setup: HP5386A counter connected to External REF. (OCXO). The input of counter connected to my DDS VFO. The frequency on VFO is 2853000 Hz. Here is what I got from counter via GPIB: S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082409E-7 S +3.505082408E-7 S +3.505082409E-7 S +3.505082408E-7 S +3.505082408E-7 S +3.505082408E-7 I converted it to following form: 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240800 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 0.00350508240900 Then I tried to use ADEV by tvb (long life to Tom!). See attached file 1b.bmp And I tried to create the charts for the collected data. See attached file 1a.bmp. But it seems I am doing something wrong. Any advises will be greatly appreciated. Thanks ! -- WBW, V.P.___ 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.
