[time-nuts] Making a HP 10811 better

Don Latham djl at montana.com
Tue Sep 20 00:32:22 UTC 2011

I have to ask again. Is there anything in the 10811 that would be
degraded by mineral oil? No condensation, even temperature distribution
throughout, or at least small gradients. The only downside I see is that
there might be some components that might be chemically degraded.


ed breya
> Yes, running everything chilled would be better if low temperature
> crystal turnovers were available. It is more complicated to chill
> than heat, of course, even today, but way back when they started
> temperature stabilizing things it was nearly impossible on a small
> scale - or at least very impractical, until the advent of TECs. It's
> also trickier to do both because there's that crossover region where
> the mode has to shift and you can get dead zones in the control
> function. Doing heating or cooling only is like a Class-A amplifier -
> much simpler to keep linear.
> I think the main problem with chilling though, is that you get
> condensation, depending on the humidity (or dewpoint), so you can't
> go very low in temperature to take advantage of lower noise and
> bias/leakage currents in devices, without encountering the
> condensation problem. For example, one of my projects involves making
> a very stable voltage standard that has the guts inside a TEC-chilled
> (or warmed) aluminum block. I plan to run it somewhere around 15-20
> deg C or so, or as low as I can without having condensation under
> most conditions, since the guts aren't going to be hermetically
> sealed inside (but maybe have a rechargeable dessicant). Another
> project involves building a log attoammeter with the input amplifier
> TEC-chilled as far down as possible (-40 to -50 deg C or so) to
> minimize bias current. This one has to be specially guarded, and with
> the cold block inside a hermetically vacuum sealed enclosure, as any
> condensation whatsoever - inside or out - could defeat the whole
> purpose.
> Ed
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"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
R. Bacon
"If you don't know what it is, don't poke it."
Ghost in the Shell

Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304

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