[volt-nuts] Traveling Standards

[Andreas Jahn]

> Hi Andreas,
> 
> In view of your comments, shouldn't we be looking at a LTZ1000 for the
> "traveller"? It's relatively expensive but not out of reach I would
> think.
> 
> John

Hello John,

a LTZ1000 is a fine thing no doubt. 
But I personally would not use it as a travelling reference. 
It might get lost or damaged during transportation.
And for this its too expensive.

Further you will need to place a short cirquit proof 
output buffer to the reference. Otherwise the Output 
Voltage will be shifted at least for several days when you
accidently short the output. A large capacitor may be
enough for a short cirquit. When the output is shorted
the temperature regulator goes to maximum temperature
and introduces some hysteresis on the chip.
Its not very easy to get the "hand adjustment" off the
LTZ1000 cirquit since the temperature setppoint 
transistor is very sensitive.
(see my cirquit from November 6th the last year).

A LM399 is stocked at Digikey for some bucks. And you
will have to add only a voltage regulator and a constant 
current source (resistor, LM334 temperature compensated,
or a simple LT1013 Opamp as Current source).
With some blocking capacitors you get a robust cirquit
with a low output impedance. (around 0.5 Ohms against
around 5 Ohms at unbuffered LTZ).

With best regards

Andreas