Re: CDV-715 Use
- 1 ATM ( atmospheric pressure) Ion Chambers, even of excellent modern
design reach their low end at about 3 mR/H full scale. This is with
every conceivable improvement, far beyond my meager efforts. Their
chief advantage is smooth response to a very wide range of energies,
again something that is achieved only with superlative design and
execution. A GM tube of any description and all sodium iodide
scintillators have a big swing in their energy response, some of
which can be corrected for at the expense of ultimate sensitivity (
energy compensated GM tubes are wrapped in lead or cadmium).
Basically the wrap cuts down the lower energies, making the overall
response from the tube more linear.
Energy response is the parameter that would make one isotope read
say, 1 mR/H when another isotope of the same field strength would
read 10 mR/H.
Very sensitive ion-chambers are made with high pressure inside, as
much as 10X atmosphere or about 150 pounds per square inch. These
offer smooth energy response and extreme sensitivity down to the
microR/H. Usually these are coupled with sophisticated computerized
electronics, especially in the environmental monitoring mode.
Handheld units are likewise very complex and needless to say
expensive to the extreme. Earlier, much simpler versions would
include the RADECTOR series, but their pressure is lower and
sensitivity is of a lesser level too.
None of these would be fodder for the home lab constructor in my
opinion, as the shell material is of exotic nature, and 150 PSI lab
gas is nothing to be played around with.
Far safer are the gas flow proportional detectors. These are very
sensitive and give an output that is proportional to the number of
radiation events, making them ideal for true quantification studies.
Their design is simplicity itself, and many examples can be purchased
for peanuts on ePay. Electronics are slightly more advanced than the
ordinary handheld, but again many units by Ludlum especially are
already rated to run these detectors. The only reason they are not
much more universally used is the fact that they take a special gas
called P10, 10% methane, 90 percent Argon- not to mention special
regulators and gas flow monitors. Nonetheless, commercial systems are
available and can sometimes be had used at Home lab prices. I have
managed to put together a complete gas flow system, comprising of
Matheson regulator, Ludlum gas flow monitors, hoses with QC fittings,
and an array of different detectors.....all at modest cost but over a
long period of time. No gas has been purchased yet so I can't report
on results, but this is a definite upcoming event - funds and time
So many projects, so little time.................and far less $$$$$
--- In CDV700CLUB@yahoogroups.com, "Jim RabidWolf" <unclerabid@...>
>it actually useful (for betas) - if one took the time to add a
> On the other hand, as you well know, a slight modification an make
seconde electrometer tube as a preamp, it can be pushed even further -
the limitations of an Ion Chamber as only those of the designer's
will and imagination.
>hand with morons on e-bay pimping them as "geiger counters," the
> It's a waste of a possible good machine, really - but on the other
water's just a little muddied.
>just such a project. I refuse to pay $29.95 for a machine, purchase
> I'm looking for a few cheep 715's (good meters, not destroyed) for
in a pallet load at $1.00 each. But I'll buy that pallet at cost....
> Jim RabidWolf
> Uncle Rabid ( http://www.unclerabid.com )
> We Repair Electronic Speed Controllers
> For Asian Mini Lathes and Mini Mills
> "Just Crazy Enough To Get the Job Done"
> ----- Original Message -----
> From: Geo
> To: CDV700CLUB@yahoogroups.com
> Sent: Saturday, September 30, 2006 10:00 PM
> Subject: [CDV700CLUB] Re: CDV-715 Use
> Anyhow, we already determined the CDV 715 can double as a wheel
> and/or a single beer can cooler.
> --- In CDV700CLUB@yahoogroups.com, Chris Smolinski <csmolinski@>
> > Finally! A use for a CDV-715! (other than as a doorstop)
> > http://junkfunnel.com/sld/
> > --
> > ---
> > Chris Smolinski
> > Black Cat Systems
> > http://www.blackcatsystems.com