[time-nuts] Re: Why do have OCXO a Vref output? (was: help reviving Trimble UCCM-LPS GPSDO)

[va2hdd at ebox.net]

Hello to all members.

And also remember that properly applied, a Zener diode can be a very 
good reference.  This might be more in the Volt--Nuts class, but the 
Solartron 7081 8.5 digit DVM uses a TC Zener as a voltage reference.  Of 
course it is a selected Zener with a carefully controlled bias current 
and assorted compensation tricks, but still a Zener for a lab class 8.5 
digit DVM.

Nice and safe holidays,

Claude VA2 HDD


On 2021-12-26 12:49, ed breya wrote:
> Andy wrote:
> "... I too was surprised to see nothing more than a Zener being used
> in one case, but bearing in mind this was in a temperature controlled
> environment is not as bad as a Zener in open air."
> 
> In the OCXOs I've had opened up, they used a temperature compensated
> Zener, typically in the 1N821 class, 6.2 V, or one near 9.1 V (I
> forget the part number series). So, it could actually have a very good
> overall tempco - a TC Zener operating at a fixed oven temperature.
> These were directly regulating the internal circuit voltage, and not
> buffered, so I think the main problem with stability is the external
> loading effects on the  operating point of the TCZD. I think the first
> noticeable effect would be a drop from open-circuit reference voltage,
> when hooking up an external pot.
> 
> Ed
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