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

Magnus Danielson magnus at rubidium.dyndns.org
Tue Sep 22 17:45:58 EDT 2015


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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