[time-nuts] New frequency standard, Mercury better than Cesium?

[Magnus Danielson]

From: "Poul-Henning Kamp" <phk at phk.freebsd.dk>
Subject: Re: [time-nuts] New frequency standard, Mercury better than Cesium?
Date: Mon, 17 Jul 2006 22:30:30 +0000
Message-ID: <21862.1153175430 at critter.freebsd.dk>

> In message <20060717203222.78738.qmail at web50709.mail.yahoo.com>, Normand Martel
>  writes:
> 
> >They should be able.... the standard uses a single
> >mercury atom!! ;-)
> 
> Which interestingly enough might make them incompatible
> with the RoHS (Reduction of Harmfull Substances) regulation
> here in EU.
> 
> As far as I've understood RoHS, you can get away with trace amounts
> of heavy metals on the banned list, under a theory of environmental
> contamination, but if you include them deliberately, you're in
> violation.
> 
> Fortunately metrological equipment is easy to get an excemption for :-)

Especially since the devices we are talking about is fairly bulky and costly,
so the expectation of going in 100000s is not very high. Thus, excemption from
the rule does not really hurt the environment as consumer goods are.

Then again, we might be able to squeeze it into a (nonleaded) tincan, but a
label with pickled herring on it and it may pass relatively unnoted. :-)

I have a real Hg barometer at home in the hallway, so I check how many mm Hg I
have each morning. I feel quite tempted to steal a little Hg from the reservour
to make a Hg ion standard, but there is a lot more work than getting the atoms.
Both cesium and rubidium is harder to come by, but ebay being what it is, it is
no longer that hard if I really wanted to. I have always wondered where one
actually get these things on a commerical basis. Surely Ebay isn't a good
source. Anybody to share some light? Sources in EC is better naturally, the
closer home the better.

The list of explicit excemptions is a quite interesting reading BTW.

Cheers,
Magnus