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

Wed Sep 23 07:07:16 EDT 2015

Hi

> On Sep 22, 2015, at 11:49 PM, Bob Benward <rbenward at verizon.net> wrote:
> 
> Continuing this discussion, I have included a PDF showing the past 30days of
> EFC.  Amazingly, the drift has reversed direction!

Yes, it’s fairly common. The standard advice with OCXO’s is to leave them on 
power as much as you possibly can.  

A bit more detailed explanation:

You have multiple processes that contribute to aging. They each have different rates, and
directions. Most of them follow a exponential decay. On a crummy oscillator, you may have 
one really terrible process that dominates everything. On a good part, you will see reversals 
and multiple slopes.

Bob

>  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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>>>> Date:
>>>>>>>>>>>>> 09/05/15
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