[time-nuts] Making a HP 10811 better

[Bob Camp]

Hi

I assume they are running that at 1 to 100 seconds :)...

The simplest reason would be to stretch the 100 seconds to 1,000 seconds. Two common things that get you at longer tau are aging and temperature. If it's temperature in your case - you might be able to help that out.

Bob


On Mar 28, 2010, at 8:55 AM, EWKehren at aol.com wrote:

> Good morning
> I have a more fundamental question. Having three 10811-5071 all with Allan  
> Variance from 1 to 100 Hz well below 1 E-12 one as low as 6 E-13 why would 
> I  want to mess with them at all?
> Bert Kehren
> 
> 
> In a message dated 3/28/2010 8:32:12 A.M. Eastern Daylight Time,  
> lists at rtty.us writes:
> 
> Hi
> 
> If your zero g axis only works over a 1/100 G range, you  are looking at 
> something other than acceleration. If you have found an axis  with a zero, it 
> should be a just as much a null at 1 mG as at 1 G as at 10  G's. It's also 
> possible that your "zero" is actually a minimum below your test  resolution 
> and higher G's bring it up to the point you can measure it. There's  no 
> guarantee of a zero being there. 
> 
> Hitting the oscillator makes it  vibrate in all three axis, that's not 
> going to be suppressed regardless of  which way you have it mounted.
> 
> Bob
> 
> On Mar 28, 2010, at 12:42 AM,  WarrenS wrote:
> 
>> 
>> Humm,
>> Have to admit, I did not  consider that as a possibility before.
>> Maybe when I tap on it, its not  microphonics after all that cause the 
> freq to modulate, but the vibration of  the inside stuff that is warming it up.
>> For every action there is a  reaction and for every  nut there is a 
> wing-it-nut.
>> 
>> ws
>> *****************
>> Hi
>> 
>> If that's the result  you are getting, you are measuring something other 
> than G sensitivity.  Temperature effects possibly.
>> 
>> Bob
>> 
>> ****************
>> On Mar 27, 2010, at 11:02 PM, WarrenS wrote:
>> 
>>> 
>>> Just a friendly comment about the Zero G turn over  point and Vibration
>>> 
>>> Like Zero temp turn over, Special  orientation of the OSC ONLY works 
> good over a VERY SMALL range, (maybe a 1/100  of G change)
>>> It would not help vibration and has no effect on  microphonics which are 
> likely a bigger problem anyway.
>>> Try taping  you Osc, It's freq will go crazy if monitoring it at high 
> resolutions and  bandwidths
>>> 
>>> ws
>>> 
>>> ************************
>>> 
>>> Hi
>>> 
>>> The concrete basement floor is your friend.
>>> 
>>> Stay as  far away from the blower on the furnace as you can. If you have 
> a drop forge  in the basement avoid it as well :)....
>>> 
>>> You will  indeed have a seismograph, but not a very useful one. There's 
> not a lot of G's  at seismic frequencies unless you live in an active 
> earthquake region. The  fundamentals of G's and displacement vs frequency are in 
> your favor in that  respect.
>>> 
>>> Bob
>>> 
>>> 
>>> On  Mar 27, 2010, at 12:42 PM, Stanley Reynolds wrote:
>>> 
>>>> Is the source of the vibration important ? I'm thinking that  any 
> vibration that is not on the same axis as gravity. Walking across the lab  vs a 
> fan that is out of balance close by. Would a suspended mass mounting help  
> with vibration isolation and damping with rubber pads and springs or would  
> that just make a seismograph ?
>>>> 
>>>> Stanley
>>>> 
>>>> 
>>>> ----- Original  Message ----
>>>> From: Peter Vince <pvince at  theiet.org>
>>>> To: Discussion of precise time and frequency  measurement <time-nuts at 
> febo.com>
>>>> Sent: Sat, March 27,  2010 10:51:07 AM
>>>> Subject: Re: [time-nuts] Making a HP 10811  better
>>>> 
>>>> Warren,
>>>> 
>>>>  If you turn over an oscillator, is the frequency  change
>>>> completely reversible (to your "under 1e-12  resolution") when it is
>>>> restored?  Thinking aloud, if an  hour-glass is turned over twice, the
>>>> final level will be the  same, but the grains will be mixed.  A quartz
>>>> crystal,  however, is solid, so hopefully nothing actually moves.
>>>> Presumably the zero-G axis is with the axis of oscillation at  90
>>>> degrees to gravity?
>>>> 
>>>>  Peter (the "other" one :-)
>>>> 
>>>> 
>>>> 
>>>>> Another thing I use it  for is to test high resolution Freq meters.
>>>>> Using a  calibrated wedge that I can then slide under one edge of the  
> zero-G
>>>>> Osc box, I can
>>>>> make small,  variable, repeatable, freq changes of under 1e-12  
> resolution,
>>>>> something pretty hard to do  otherwise.
>>>>> If I want to make BIG changes like 1e-10, I can  rotate the box on any 
> of its
>>>>> sides and still use the  wedge,
>>>>> and for a quick check of new equipment, I just turn  the box over 
> which then
>>>>> gives a couple of parts in 1e-9  freq change.
>>>>> It makes a weird but simple and indispensable  variable freq source 
> that is
>>>>> useful for many things, such  as checking the LOOP TC of a TBolt.
>> 
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> 
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