[time-nuts] V refs

[Richard Moore]

On Nov 30, 2008, at 4:00 AM, Bruce wrote:

> Message: 1
> Date: Sun, 30 Nov 2008 17:26:28 +1300
> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
> Subject: Re: [time-nuts] V refs
>

> <clip>
> Does the Datron use a series stack of zeners or does it use the once
> popular ring of 2 reference circuit?
>
> Bruce

Bruce, the 1082 uses two sets of two zeners in series. Each series  
set of zeners has its own current setting resistor set. The out put  
from each zener string is fed thru a 9.1k resistor into the + input  
of an opamp mixer which drives an emitter follower, and that drives  
the current setting resistors for the zeners, and, divided down, the  
ref. output for the meter. The system actually works very well, but  
given the ages of these meters, I suspect that the zero TC current  
point of the zeners might need tweaking. The opamp is a Fairchild  
uA714CH. I'm not familiar with its noise performance or, in this  
system, its input temp characteristics -- I'll bet this also would be  
a good spot for a chopper amp, if I switch to a LTZ1000....

Dick Moore