On Nov 30, 2008, at 4:00 AM, Bruce wrote: > Message: 1 > Date: Sun, 30 Nov 2008 17:26:28 +1300 > From: Bruce Griffiths <[EMAIL PROTECTED]> > 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 _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
