[time-nuts] Sign of Time Interval & SR620 Hint 2

Brooke Clarke brooke at pacific.net
Sat May 20 15:23:05 EDT 2006


Not knowing which direction to move the C-field, I tried 000 where 500 
is probably more like correct.
The result on s/n 1013 is no change, in the TI when compared to s/n 1227 
that's probably near 1E-13.  The difference between the two cesium 
standards is 9.9E-12 and changing the C-field on s/n 1013 has no effect.

s/n 1013 is the one the shipper did not put in the Jiffy-box, and 
instead metal banded to the pallet. 
I think there is a problem with the C-field circuitry.  Maybe that's why 
the green Lock LED is on but it can't be set.

This is very easy to see when using a good cesium as a reference.

------------------SR620 Hint #2 --------------
The External reference can be either 5 or 10 MHz, but not 1 MHz.  If you 
connect a 1 MHz source to the ext ref input it confuses the counter, 
i.e. may change in internal reference frequency value.  To fix that you 
need to go into the CAL menu and set the frequency to 10000000.

Also after moving the jumper on the PCB to enable cal constants (I'm 
leaving it there since I'm the only person using this counter)  you can 
use the front panel keys to view and change internal calibration 
constant #4 which can be between 0 and 4095.  This is the control 
voltage to the internal 10.0 MHz oscillator.  Mine was slow 17 Hz and 
changing the cal constant from 02038 to 01957 brought it back to within 
0.01 Hz.  This might make it easier for locking to the external reference.

Have Fun,


w/Java http://www.PRC68.com
w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml

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