Warmup data on the HP 10811: Here is some data collected on the internal HP 10811 timebase in my HP 5370A counter, which had been turned off and plugged off for about 3 days.
21:39:25, 9999798.6 21:39:35, 9999806.0 21:39:46, 9999822.6 21:39:55, 9999836.8 21:40:06, 9999853.2 21:40:15, 9999866.8 21:40:26, 9999881.7 21:40:35, 9999892.4 21:40:46, 9999904.1 21:40:56, 9999913.1 21:40:58, 9999915.2 21:41:07, 9999923.0 21:41:16, 9999930.1 21:41:25, 9999936.5 21:41:36, 9999944.0 21:41:46, 9999949.3 21:41:55, 9999954.3 21:42:06, 9999959.9 21:42:15, 9999964.0 21:42:26, 9999968.6 21:42:35, 9999971.8 21:42:45, 9999975.2 21:42:54, 9999977.9 21:43:05, 9999981.0 21:43:17, 9999983.9 21:43:26, 9999985.9 21:43:35, 9999987.8 21:43:46, 9999990.0 21:43:55, 9999991.3 21:44:07, 9999992.9 21:44:16, 9999994.0 21:44:25, 9999994.9 21:44:36, 9999996.1 21:44:45, 9999996.9 21:44:56, 9999997.7 21:45:06, 9999998.3 21:45:15, 9999998.9 21:45:17, 9999999.0 21:45:19, 9999999.1 21:45:21, 9999999.2 21:45:24, 9999999.3 21:45:26, 9999999.4 21:45:36, 9999999.7 21:45:45, 9999999.8 21:45:56, 9999999.9 21:46:05, 9999999.9 21:46:08, 9999999.9 21:46:10, 10000000.0 After that, the display was a stable 10,000,000.0 for the next 15 minutes (one reading was 10,000,000.1), then I stopped the data collection. The counter used was the HP 5334B with the Thunderbolt as external reference. Ambient temperature: about 22 degrees C (cool) Bottom line: about 200 Hz from a cold start and about 7 minutes to within 0.1 Hz of final frequency. Didier KO4BB Didier Juges wrote: > That is interesting. I have not checked the 10811 for that particular > behavior, but I have checked a number of cheap, non TC crystal oscillators, > and the initial drift has always been much smaller, in the order of 100's of > Hz, not 1,000's, scaled for 10 MHz. > > I refer to the crystal oscillators inside my various ham radio gear and > non-TCXO controlled instruments, such as the 5334B counter I have. > > It may be due to the fact that the crystal in the HP 10811 is optimized for > flat temperature sensitivity around the operating point of the oven, when the > cheap crystals I have checked are optimized around ambient (if they are > optimized at all). > > I have several 10811's here (one by itself, the others inside instruments) > and now that you picked my attention, I have to do the test :-) > > It's easy to plot it against the Thunderbolt with a counter hooked to the > GPIB controller and with my logging software running. I shall report here > soon :-) > > Didier KO4BB > > > ---- Jeroen Bastemeijer <[EMAIL PROTECTED]> wrote: > >> Dear Time-nuts, >> >> Just a quick experiment. I started with the cold 10811 OCXO (switched >> off for >24 hours). I connected it to a counter and noted the frequency >> every 30 seconds. (last two measurement each 5 minutes). >> >> You can see the curve in the attached PDF. The offset at t=0 was 1706 Hz >> (Compared to 10.000000MHz). >> >> After 10 minutes warm-up the total offset is 0.75Hz (compared to >> 10.000000MHz) and offset is 0.12Hz from the "final" value. According to >> the spec the offset should be within 5*10^-9. >> >> From this I conclude the oscillator is not faulty. Sorry, Didier ;-) >> >> The possible reason for this offset is probably not the crystal, but the >> tempco of the rest of the circuit. The oven heats up till about 82 >> degrees centigrade. A PN-juntcion at room temperature (22 degrees) will >> increase 60 degrees in temperrature, it's forward voltage will change by >> approx. 120 mV!!!!! This change will lead to a significant change in >> circuit properties (e.g. of the oscillator and the attached AGC circuit). >> >> Probably this was the reason HP specfied it's oscillator first after 10 >> mins of warm-up. >> >> This makes me wonder: If an oscillator gives a big offset, the >> ovencontroller may be faulty... not working at all, or not getting warm >> enough. >> >> Jeroen PE1RGE >> >> >> >> The raw data: >> Time Frequncy [MHz] Offset [Hz] >> 0 9,998294 1706 >> 30 9,998405 1595 >> 60 9,998645 1355 >> 90 9,998854 1146 >> 120 9,999038 962 >> 150 9,999197 803 >> 180 9,999349 651 >> 210 9,999466 534 >> 240 9,999569 431 >> 270 9,999666 334 >> 300 9,99974 260 >> 330 9,999804 196 >> 360 9,999858 142 >> 390 9,999906 94 >> 420 9,99994027 59,73 >> 450 9,99996696 33,04 >> 480 9,99998633 13,67 >> 510 9,99999979 0,21 >> 540 10,00000062 -0,62 >> 570 9,99999958 0,419999999 >> 600 9,99999925 0,75 >> 900 9,99999933 0,67 >> 1200 9,99999937 0,630000001 >> >> >> Didier Juges wrote: >> >> >>> That sounds like an awful lot of drift, absolutely inconsistent with a >>> crystal oscillator of any kind. >>> >>> Either this OCXO is really sick, and just happen to end up at the right >>> frequency by accident, or it is an OCO (Oven Controlled Oscillator :-) >>> >>> Didier KO4BB >>> >>> Jeroen Bastemeijer wrote: >>> >>> >>> >>>> Dear Rick, >>>> >>>> Are you sure the 500Hz is too much for a cold oven? I checked my 5345A >>>> (recently acquired) counter, which was switched off for some time. >>>> Measuring the frequency directly after applying power and switching on, >>>> resulted in about 1640 Hz frequency offset. After warm up, the error is >>>> below 0.4 Hz. (The unit used here is a 10811a). The error drops pretty >>>> fast, allthough I didn't measure an accurate curve. Is the frequency >>>> difference caused by the tempco of the oscillator circuit? >>>> >>>> Cheers, 73s Jeroen PE1RGE >>>> >>>> >>>> >>>> >>> _______________________________________________ >>> time-nuts mailing list >>> time-nuts@febo.com >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> >>> >>> >>> >>> >>> >> -- >> Ing. Jeroen Bastemeijer >> >> Delft University of Technology >> Department of Electrical Engineering >> Electronic Instrumentation Laboratory >> Mekelweg 4, Room 13.090 >> 2628 CD Delft >> The Netherlands >> >> Phone: +31.15.27.86542 >> Fax: +31.15.27.85755 >> E-mail: [EMAIL PROTECTED] >> >> > > > _______________________________________________ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts