Hi Jerry, See AN4776 on st.com. Section 2.6 looks particularly interesting.
Orin. On Mon, Apr 24, 2017 at 12:06 PM, Jerry Hancock <[email protected]> wrote: > This is an exercise more than anything. It started when I noticed the > counter in a 3586B I purchased was +1 count unless I dropped the input > frequency .25hz. I was using my GPSDO reference for it and the 3336 it was > counting. I then took my GPSDO and tried reading that directly and I see > the same thing. This is annoying more than anything and I assume there is > a slight gate phase related issue. I don’t have anything to read the > jitter on my GPSDO which is a Lucent RFTG-U with the REF1 and REF0 but > since I am using it as the reference and the signal under test, it > shouldn’t matter at .1hz. If I run the count over 3 minutes, the count is > .923hz high consistently. To put a finer point on it, reading > 10,000,000.00hz from my GPSDO, It will read consistently 10,000,000.1 or > 10,000,000.0 with the distribution of each to average 10,000,000.923 over 5 > minutes. If I drop the input frequency by .25hz, it will read 10,000,000.0 > without a 10,000,000.1 until the cows come home. I’ve > let it run about a day to check. > > So I was thinking, o.k., let’s put a frequency counter on the back to read > the F0 output signal rom the 3586B and see what it reads but I then > realized I don’t have anything that accurate. I do have a lot of micro > processors around, everything from the lowly PIC thru the DSPIC to the > STM32F7’s, F4’s and if I have to, I will get a FPGA and go from there. I > could purchase an HP 12 digit counter if I could find one locally as I am > tired of paying shipping but haven’t found one to date. > > So no really pressing reason for the counter other than just curious as to > what is causing the issue with the 3586B. By the way, when I read any of > the WWV signals they count +.1hz as well under constant signal. I am > pretty sure the 3586B is recognizing my reference input as the OCXO is > dialed to 10,000,000.0 and the standard oscillator is a little high at +.4 > (if I disconnect the OCXO strap) and I haven’t looked into it yet. > > Thanks for the interest and help > > Jerry > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
