[time-nuts] Tbolt Damping setting

[WarrenS]

Tbolt users,

One of the questions I often hear is what should the Tbolt's Damping be set to?
Assuming the Dac_Gain and TC_Sec are correctly set, then Damping is the easy one;

1) If your concerns are freq accuracy and you don't care about Phase accuracy, 
Set the damping from 1 to 1.5  with the Factory default of 1.2 being a good Nominal Value.

2) If your concerns are Phase accuracy and are willing to accept some increase in freq noise, 
Set the damping from 0.5 to 0.7  with  0.6 a good nominal value.

3) And for a compromise between both Phase and Freq 
Set the Damping from 0.7 to 1.0, with 0.85 a good nominal value. 

Lower damping settings < 1.0  are best used only with longer TC settings > 100  

The non technical description of what damping does (in the Tbolt) is:  
The TC setting is the Tbolt's Freq correction Time Constant  (short term Osc error)
and the Damping setting effects the Tbolt's Phase correction time. ( Long term Phase error)
The way that Damping controls Phase is by causing the Freq error correction to Overshoot.

As to how much difference changing the damping makes.
The difference in phase error between slow and fast damping setting can be 10 to 1 
when the TC is set to the high value needed to get best freq noise.

Hope this clears up some of the Damping setting questions.
Attached shows the response with various TC and Damping settings

ws
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Tbolt Damping.GIF
Type: image/gif
Size: 54144 bytes
Desc: not available
URL: <http://febo.com/pipermail/time-nuts_lists.febo.com/attachments/20091214/cd8bab74/attachment.gif>