[time-nuts] Bad batch of HP10811's
Jeroen Bastemeijer
J.Bastemeijer at TUDelft.nl
Fri Feb 16 14:45:47 UTC 2007
Dear Time-nuts,
New info on an old subject:
I opened the counter (5345A) to check what kind of oscillator was
inside. It was a 10544A instead of a 10811A!!!
I checked for a datasheet of the 10544 but I couldn't find it. Luckily I
ran across an article in HP Journal. See the quote below:
Warmup. The 10811A/B Oscillator cuts the 10544/B/C
warmup time specification in half: 10 minutes for the
10811A/B compared to 20 minutes for the 10544A/B/C Oscillator.
Warmup time is defined as the time between oscillator
oven turn-on and the time when the output frequency
is within 0.05 Hz of the operating frequency, In portable
instruments, where battery weight must be minimized, low
power and quick warmup are crucial. Since the instrument
warmup time is likely to be much shorter than the oscillator
warmup time, the latter usually dominates. A side benefit of
the 10811A/B is that its frequency just after oven turn-on is
only 100 Hz low compared to 1 kHz low for the 1054aA/B/C.
This allows faster lock-in for instruments using phaselocked
loops.
Bottom line: The 10544 gives a higher offset at switch-on compared to
the 10811.
Only thing to do now is find a datasheet to verify it with real numbers,
as my oscillator was 1700 Hz off (compared to 1 kHz in the article) and
Didiers' oscillator was 200Hz off (compared to 100 Hz in the article).
Is there a link to the 10544 datasheet somewhere out there???
Have a nice weekend, Jeroen
Didier Juges wrote:
>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 <J.Bastemeijer at TUDelft.nl> 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 at 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: J.Bastemeijer at TUDelft.nl
>>>
>>>
>>>
>>>
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>>
>>
>>
>
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>
>
>
--
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: J.Bastemeijer at TUDelft.nl
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