[time-nuts] Z380XA The saga of the aging 10811

[Bob Benward]

Continuing this discussion, I have included a PDF showing the past 30days of
EFC.  Amazingly, the drift has reversed direction!  Anyone have any insights
into this behavior?  Each data point represents 10 seconds.

Bob

>>> -----Original Message-----
>>> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Magnus
>>> Danielson
>>> Sent: Tuesday, September 22, 2015 5:46 PM
>>> To: time-nuts at febo.com
>>> Cc: magnus at rubidium.se
>>> Subject: Re: [time-nuts] Z380XA The saga of the aging 10811
>>> 
>>> Analog is nice and dandy, but for longer time-constants, digital does
have it's
>>> merits.
>>> 
>>> Wonder how good resolution one really need for sensing and how to
achieve
>>> it.
>>> 
>>> Cheers,
>>> Magnus
>>> 
>>> 
>>> On 09/15/2015 12:58 PM, Bob Camp wrote:
>>> > Hi
>>> >
>>> > To the extent that the oven controller is an integrator, it only
>>> > integrates over a couple of seconds.
>>> >
>>> > Bob
>>> >
>>> >> On Sep 14, 2015, at 5:58 PM, Bob Benward <rbenward at verizon.net>
>>> wrote:
>>> >>
>>> >> Robert,
>>> >> The drift has slowed down to something around 8xE-10, which is a bit
>>> >> over the spec of <5E-10.  But this is the single oven, I have not
>>> >> reassembled the double oven yet.
>>> >>
>>> >> If the oven regulation was off, I would suspect I would see the EFC
>>> >> go back and forth a bit, maybe a general trend up, but some retracing
>>> >> would be expected.  The oven control is an integrator, so unless the
>>> >> offset is very large compare to the output of the thermistor, a
>>> >> continuously changing offset voltage will not have a large effect on
>>> >> setpoint.  A crystal resonator will drift about 1-5E-8/degC, so I
>>> >> guess a loose temperature control would certainly exhibit the drift I
am
>>> seeing.
>>> >>
>>> >> Bob
>>> >>
>>> >>
>>> >>
>>> >>>>> -----Original Message-----
>>> >>>>> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of
>>> >>>>> George Atkinson
>>> >>>>> Sent: Monday, September 14, 2015 2:42 PM
>>> >>>>> To: Discussion of precise time and frequency measurement
>>> >>>>> Subject: Re: [time-nuts] Z380XA The saga of the aging 10811
>>> >>>>>
>>> >>>>> Well, if the batch/revision of op-amps had a doping, contamination
>>> >>>>> or
>>> >> similar
>>> >>>>> issue, the input offset could be drifting fairly constantly
>>> >>>>> causing a temperature channge in one direction.
>>> >>>>>
>>> >>>>> Robert G8RPI.
>>> >>>>>
>>> >>>>> On 9 September 2015 at 04:40, Bob Benward
>>> <rbenward at verizon.net>
>>> >>>>> wrote:
>>> >>>>>
>>> >>>>>> Hi Ed,
>>> >>>>>> OK, a bad oven.  I can buy that.  But then if the oscillator is
>>> >>>>>> constantly drifting, would that not imply that the oven is
>>> >>>>>> constantly changing temperature, in one direction?
>>> >>>>>>
>>> >>>>>> BTW, the curve is starting to flatten out.  It might be flat
>>> >>>>>> before It gets to 1000K counts.
>>> >>>>>>
>>> >>>>>> Bob
>>> >>>>>>
>>> >>>>>>>>> -----Original Message-----
>>> >>>>>>>>> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf
>>> >>>>>>>>> Of ed breya
>>> >>>>>>>>> Sent: Tuesday, September 08, 2015 10:55 AM
>>> >>>>>>>>> To: time-nuts at febo.com
>>> >>>>>>>>> Subject: Re: [time-nuts] Z380XA The saga of the aging 10811
>>> >>>>>>>>>
>>> >>>>>>>>> It could be that the inner oven temperature regulation is off
>>> >>>>>>>>> a bit, or
>>> >>>>>> even
>>> >>>>>>>>> failed. There was a report at one of the popular time-nuts
>>> >>>>>>>>> oriented
>>> >>>>>> websites (I
>>> >>>>>>>>> forget which one, but it's the one that had extensive coverage
>>> >>>>>>>>> of the
>>> >>>>>> Z3801A)
>>> >>>>>>>>> about inner oven problems a few years ago. I took mine apart
>>> >>>>>>>>> and found
>>> >>>>>> that
>>> >>>>>>>>> it had an IC of a particular date code range that was prone to
>>> >> failure.
>>> >>>>>> I can't
>>> >>>>>>>>> recall whether I replaced it with the same type but different
>>> >>>>>>>>> date, or
>>> >>>>>> an
>>> >>>>>>>>> alternative, but it worked just fine after that, with no
>>> >>>>>>>>> tweaking of
>>> >>>>>> coarse EFC
>>> >>>>>>>>> needed.
>>> >>>>>>>>>
>>> >>>>>>>>> The IC was a dual opamp I think, that controlled the oven
>>> >>>>>>>>> temperature according to the thermistor signal, and drove the
>>> >> heater
>>> >>>>> transistor(s).
>>> >>>>>>>>> It was a fairly high performance type, but not that unusual. I
>>> >>>>>>>>> think it
>>> >>>>>> was a
>>> >>>>>>>>> Linear Technology brand part.
>>> >>>>>>>>>
>>> >>>>>>>>> Ed
>>> >>>>>>>>> _______________________________________________
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>>> >>>>>>>>> Version: 2015.0.6140 / Virus Database: 4409/10580 - Release
>>> Date:
>>> >>>>>>>>> 09/05/15
>>> >>>>>>
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