[time-nuts] How to create a super Rb standard

Chris Albertson albertson.chris at gmail.com
Wed Jan 18 20:37:14 EST 2017

On Tue, Jan 17, 2017 at 9:23 PM, Li Ang <379998 at qq.com> wrote:

> Hi
> I am wondering if anyone tried to put a Rb unit into a vacuum container.
> And how much the performance is improved?

Vacuum is a VERY good thermal insulator.   If the electronics used even
just a few watts of power you'd need some way to cool it, other then
convection.    Almost all electronics depends on air for cooling.  You'd
need to redesign it for conductive or radiative cooling.   That is not easy.

I did something very simple that works.   I placed the Rb unit in a metal
box and used a thermostatically controlled fan. The fan speed is controlled
by a PID controller.  It all runs on one 8-pin AVR chip,  I use two analog
inputs for two temperature sensors (one epoxied to a heat sink and one in
free air.  Another pin is analog output to control the fan speed.   In
improvement would be to use a three wire fan with a tachometer.

I tried before to make an analog fan controller but without using a dozen
op amps it is hard to implement any kind of decent algorithm.

But BEFORE you try and improve the Rb performance you need to have some way
to MEASURE its performance.  This is likely much harder.

Chris Albertson
Redondo Beach, California

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