[time-nuts] What's the latest correct PICTIC II Mouserproject?- Heathkid

Stanley Reynolds stanley_reynolds at yahoo.com
Sat Aug 14 16:41:36 UTC 2010


1) I have no previous experience building precision anything, I'm not an expert.

2) My guess is the design expects quality components and depends on the auto 
calibration to correct any component drift.

Short term stability between calibrations is what we want. The absolute value of 
C16 and C17 is not as important as it's stability in leakage and value. 


Guess we could put the didoes in a constant temp oven but not sure all the 
components are more stable at higher temps.

Good ideas about didoes here : 
http://www.sciencebuddies.org/science-fair-projects/project_ideas/Elec_p033.shtml

(note Figure 3 and how the didoes voltage drop is more linear at higher temps vs 
room temp.)

 
Figure 3. 

Stanley

 



________________________________
From: Heathkid <heathkid at heathkid.com>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
Sent: Sat, August 14, 2010 10:43:15 AM
Subject: Re: [time-nuts] What's the latest correct PICTIC II Mouserproject?- 
Heathkid

Okay Stanley... I've got a Tektronix 370A curve tracer at work.  So the diodes 
need to be matched?  No problem.

So I match the diodes and the resistors to within 0.001%.  Are there any other 
components that need matched?  Also, you mentioned using hemostats as heatsinks 
on the diodes while installing them.  I know that diodes make very good 
temperature sensors as well.  Are there any suggestions on keeping them stable 
after they are on the board?  What is the recommended operating temperature of 
the PICTIC II?

Thanks.

73 Brice KA8MAV

----- Original Message ----- From: "Stanley Reynolds" 
<stanley_reynolds at yahoo.com>
To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
Sent: Saturday, August 14, 2010 10:43 AM
Subject: Re: [time-nuts] What's the latest correct PICTIC II Mouserproject?- 
Heathkid


<snip>

Maybe we should buy lots of diodes to match them, they are relative cheap, also
use extra care installing them. Using hemostats as heat sinks and just enough
heat for a good connection do not want to damage/change them after the match.

Stanley 

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