[time-nuts] Ovens

Brooke Clarke brooke at pacific.net
Tue Aug 17 13:51:56 EDT 2004

Hi Rick:

Is E1938A something I could search eBay for, or are there other HP model 
numbers that encompass the E1938A?
i.e. how to get one of these?


Brooke Clarke, N6GCE


Rick Karlquist wrote:

>Brooke Clarke said:
>>HP did quite a bit of research on isothermal oven design.  The idea is
>>that you can draw a line in three dimensional space where the
>>temperature is constant.  Since you can not have the temperature sensor
>>and the device being controlled in the same place it's important to have
>>them both on an isothermal line.  Then the trick is to get the system
>>gain as high as possible.
>In the 10811, this is accomplished by ratioing the power to
>2 heater transistors.  You can tweak the ratio in an individual
>10811 to optimize its thermal gain.  A thermal gain of about 1000
>can be achieved.  The E1938A goes beyond this theory, and keeps
>the temperature constant over a volume, not a line.
>(See http://www.karlquist.com/oven.pdf).  A thermal gain of
>over 1,000,000 can be achieved in a single (not double) oven this
>Rick Karlquist
>time-nuts mailing list
>time-nuts at febo.com

More information about the time-nuts mailing list