[time-nuts] Shera revisted

EWKehren at aol.com EWKehren at aol.com
Wed Aug 10 09:33:30 EDT 2016


I get repeated requests for info on Shera mainly for Rb applications. Shera 
 has a successful history controlling Rb's.  Two things are a problem. The  
AD 1861 is not only unavailable but also never intended for precise DAC  
applications. The LTC 1655 makes a perfect replacement ,16 bits is more than  
enough and covers range and resolution. What is needed is someone proficient 
 with PIC assembly programming. We have the recommended changes.
Second logic IC's are also outdated and hard to get. The solution is simple 
 an Altera 32 cell 10 nsec. gate array, readily still available for less 
than $  2, we have done a design and will gladly share once the PIC has been 
modified  and tetsted.
With the work on the HP 5065A adding pressure compensation and temperature  
will be relatively simple using the 1655 with its reference output.
On the PIC issue please contact me directly off list
Bert Kehren 
 


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