[ RadSafe ] X-Ray Spectrometer Safety considerations

[Bob Westerdale]

Greetings:
        I'm working on a design spec for an X-Ray Fluorescence 
spectrometer we're developing,  and I have a couple of Safety-related ( 
note requisite RadSafe tie-in!) items that I hope to get some feedback 
on.......
        1.      Color of the fail-safe 'X-Ray On'  lamp.    In the US, a 
yellow lens with the traditional magenta trefoil has been the accepted 
standard for quite a            while.   Years ago,  I did run into some 
problems when shipping instruments overseas where a red lens was needed. 
Could some of our                       International  folks comment on 
this?  colors/labelling/location, etc.

        2.      Electrical circuitry for initiation of X-ray power and 
Safety Interlock circuits.   Years ago,  before microprocessors took over 
the world,  X-Ray On            functions were basically push-buttons and 
latching relays.  These circuits we required to be 'floating',  ie 
transformer powered so that a problem                   like a ground 
fault ( eg. pinched or abraded wire)  could not inadvertently turn on the 
X-Ray power.   I believe the German regs even called for 
                redundant circuits,  so that the failure of one circuit ( 
while unlikely) would not result in the chance of an accident.    These 
days,  most digital                     designers ( well, at least the 
ones I work with!) scoff at the idea that there could be a code problem or 
blown logic gate that might leave the X-ray             status in 
question.   However, most of us have had a piece of digital equipment crap 
out  ( HW or SW) at very bad time;  the potential damage from           an 
accidentally powered analytical X-ray tube is both immediate and long 
lasting.

        I'd be quite interested in hearing the community views on these 
matters, 

        Thanks!

        Bob Westerdale
        RSO,  EDAX Inc.