[time-nuts] Fine print on HP 5334B

[Hal Murray]

(Interesting timing given the SR620 discussion.)

I'm (finally) getting my GPIB gizmo working.

I have a HP 5334B running off its (good) internal osc looking at the output 
of a Z3801A.  Assuming the Z3801A is stable, this is a backwards way of 
looking at the internal osc.  (There is a shared in/out connector for the 
internal clock, so I can't see the internal osc if I feed it an ext 
reference.)

I left it running for a night with the mostly default setup and 100 cycle 
averaging.  I think the default gate time is 0.3 seconds.  Answers ranged 
from:
  F  +9.999999330E+06
  F  +9.999999333E+06

I've had this setup running for several weeks.  The bottom digit doesn't fit 
on the display, so I never noticed there was anything interesting going on 
down there.  The 100 cycle averaging has a button on the front panel.  
Without it, the display is one digit shorter.

Yesterday, I got it running with a single 60 second gate.   Now it's wobbling 
between:
   F  +9.999999339E+06
   F  +9.999999340E+06

I was a bit surprised there is such a difference.  Is this all obvious to 
anybody who has carefully read the manual?

Of course, now that I think about it, averaging frequency measurements seems 
less helpful that simply using a longer measurement time.  But I'm still 
surprised the answers were so different.

Another quirk I noticed.  They truncate rather than round for the display on 
the front panel.  9.999999339 shows up as 9.99999933 rather than 9.99999934


Is there anything else like this I should watch out for?  Does anybody have a 
quick summary on how to get good results or traps to avoid?

-- 
These are my opinions, not necessarily my employer's.  I hate spam.