Loading ...
Sorry, an error occurred while loading the content.

Source for used Gieger counters

Expand Messages
  • teleronni
    A CD V-700 modified to read 50 r/hr would be ideal(?). Open to ieas/suggestions. Thanks
    Message 1 of 8 , Sep 4, 2005
    • 0 Attachment
      A CD V-700 modified to read 50 r/hr would be ideal(?). Open to
      ieas/suggestions.

      Thanks
    • n5tsx
      If you are around ANY source that requires an insturment to be reading that high a value, you are either in the industry(and you would know there are far
      Message 2 of 8 , Sep 4, 2005
      • 0 Attachment
        If you are around ANY source that requires an insturment to be
        reading that high a value, you are either in the industry(and you
        would know there are far better meters for reading that level), or you
        have alot to learn about radiation, it's effects, and how to avoid
        just such a level at all costs. My $.02's worth. Phil N5TSX




        --- In CDV700CLUB@yahoogroups.com, "teleronni" <telewinze@a...> wrote:
        > A CD V-700 modified to read 50 r/hr would be ideal(?). Open to
        > ieas/suggestions.
        >
        > Thanks
      • Geo
        ... Let me address this question from a technical standpoint. True, most of us in this hobby want low range, high sensitivity detectors and systems. We have
        Message 3 of 8 , Sep 4, 2005
        • 0 Attachment
          --- In CDV700CLUB@yahoogroups.com, "teleronni" <telewinze@a...> wrote:
          > A CD V-700 modified to read 50 r/hr would be ideal(?). Open to
          > ieas/suggestions.
          >
          > Thanks

          Let me address this question from a technical standpoint.

          True, most of us in this "hobby" want low range, high sensitivity
          detectors and systems.
          We have easily reached the maximum sensitivity allowed by nature and
          physics, considering the ambient
          background radiation, and have then exceeded that level by another
          order of magnitude by building shields to
          reduce the background.

          There exists another portion of our "hobby" that are interested in
          radiation detectors for other reasons than pure
          science, at least to some extent or the other. These fall into many
          subgroups, but we sort of lump them into
          the "War Meter" category, that is high range, low sensitivity
          detector units.

          Back in the Cold War days, the best technology available for a high
          range meter was the ion-chamber.
          These are embodied in the CDV-705 and CDV-71X series.
          For some applications this remains true even today. Ion-chambers are
          by nature typically less sensitive than a GM tube, but this is not
          always the case. Certain designs, particularly the ones which operate
          at a high internal pressure, can be quite sensitive.
          In addition, these advanced designs share a common feature of all ion-
          chambers, namely they have a tremendous dynamic
          range, and react very similarly to all energies of gamma radiation.
          GM tubes are not linear in the same way, and will respond
          way differently to gamma rays of different energies unless they are
          intentionally "energy compensated" by the addition of metallic
          filters ( this also cuts the counts way back for certain energies-
          basically the probe is reduced in overall sensitivity to match the
          least sensitive area of its response curve)

          I myself don't rely on the CDV-71X ion-chamber units much mainly
          because they are SO insensitive, overall
          operation can never be verified with civilian rad sources.

          Lets now look at some common GM tubes, their maximum usable ranges,
          some alternatives, and point out a few unusual instruments that may
          fill both roles, science and war.

          Pancake probe, LND 7311 my favorite for most science and
          environmental rad measurements. Very sensitive, actually the
          most sensitive of all 900V alpha-beta-gamma GM tubes> returns 60 CPS
          for every 1 mR/H of Co-60
          ( a standard radiation source for almost all probe calibrations now).
          60 CPS is 3600 CPM, derated to 3300 opn most scales, but
          this tube tops out at about 166 mR/H, usable but not accurate to 200
          mR/H..

          Next in line would be the very common beta-gamma tube, LND Model 725,
          used in Ludlum, Eberline and most other modern Hot-Dog probes. This
          is the modern improved equivalent of the venerable 6993 of the
          1960's. Beta-Gamma only, sensitivity of 20 CPS. Tops out at about 500
          mR/H @600K CPM, in reality, limited to 200 mR/H.

          Jumping way down in sensitivity is the LND Model 715 tube, giving a
          return of only .5 CPS (30 CPM)per 1 mR/H. On a
          Ludlum Model 3 meter, the max CPM readout is 500,000, so max reading
          would be 16 R/H. Using a meter with a higher count range (X1000)
          would allow an even higher reading to be taken, but not as much as
          the range extension would indicate.
          NOTE this is a 500V tube, not directly exchangeable with a 900V tube
          until voltage is adjusted.

          At the highest range, you would select something like a LND Model
          7161, which gives .26 CPS and 32 R/H. This can even be extended to a
          little higher if a special meter with a X1000 scale is used. Also a
          500V tube.

          Caveat: very high range GM tubes will do the job, but just like very
          high range ion-chambers, can't be tested with civilian level rad
          sources.
          All GM tubes suffer from dead-time or paralysis issues at high end
          making them non linear.

          For a complete chart of all the LND tubes, arranged according to
          their Gamma Sensitivity see:
          http://www.lndinc.com/gammaref.htm

          Another company called Eurysis makes a line of small glass GM tubes
          that are well suited to high range applications, but they have been
          bought up by someone and I lost the link.


          High Range Meters with built in probes:

          Ludlum Model 14C. Has a connector for a typical external GM, but also
          has an internal high range , energy compensated
          GM that is good out to 2000 mR/H. Internal probe used only on the
          X1000 scale.

          Ludlum Model 5 Geiger Counter ( most others are actually ratemeters
          or survey meters). 2 built-in high range energy compensated GM
          tubes. Covers 0-2000 mR/H

          Modern Ion-Chamber units with sound!:

          Ludlum Model 9 > 0-5000 mR/H. Very cool, my favorite unit, can read
          home lab strength sources on lowest ranges. Also can be tested using
          a Beta source. Has Beta shield.

          Ludlum Model 17 High Range Ion Chamber > 0-50,000 mR/H, my "war
          meter", can actually detect civilian samples. Has Beta shield.



          Geo
        • DH
          Phil, I think this was a zen riddle. There are two solutions, one complex involving dealing with electronically driving & handling an otherwise overdriven
          Message 4 of 8 , Sep 5, 2005
          • 0 Attachment
            Phil,

            I think this was a zen riddle. There are two solutions,
            one complex involving dealing with electronically driving & handling
            an otherwise overdriven tube; and the simple one consisting
            of a barrel of sand with the probe inside.



            --- In CDV700CLUB@yahoogroups.com, "n5tsx" <n5tsx@n...> wrote:
            > If you are around ANY source that requires an insturment to be
            > reading that high a value, you are either in the industry(and you
            > would know there are far better meters for reading that level), or you
            > have alot to learn about radiation, it's effects, and how to avoid
            > just such a level at all costs. My $.02's worth. Phil N5TSX
            >
            > --- In CDV700CLUB@yahoogroups.com, "teleronni" <telewinze@a...> wrote:
            > > A CD V-700 modified to read 50 r/hr would be ideal(?). Open to
            > > ieas/suggestions.
            > >
            > > Thanks
          • Ron
            Why not this surplus tube as a spare? Whats the ups and downs? PROBE 5980 THESE PROBES WERE USED IN THE SEVERAL MILITARY COUNTERS TO EXTEND THE RANGE UP TO
            Message 5 of 8 , Sep 5, 2005
            • 0 Attachment
              Why not this "surplus" tube as a spare? Whats the ups and downs?

              PROBE 5980 THESE PROBES WERE USED IN THE SEVERAL MILITARY COUNTERS TO
              EXTEND THE RANGE UP TO 500mR/hr. EASILY ADAPTABLE TO THE CDV-700 FOR
              RANGE EXTENSION.

              It's about $30 plus shipping.


              --- In CDV700CLUB@yahoogroups.com, "DH" <revtkatt@y...> wrote:
              >
              > Phil,
              >
              > I think this was a zen riddle. There are two solutions,
              > one complex involving dealing with electronically driving & handling
              > an otherwise overdriven tube; and the simple one consisting
              > of a barrel of sand with the probe inside.
              >
              >
              >
              > --- In CDV700CLUB@yahoogroups.com, "n5tsx" <n5tsx@n...> wrote:
              > > If you are around ANY source that requires an insturment to be
              > > reading that high a value, you are either in the industry(and you
              > > would know there are far better meters for reading that level),
              or you
              > > have alot to learn about radiation, it's effects, and how to avoid
              > > just such a level at all costs. My $.02's worth. Phil N5TSX
              > >
              > > --- In CDV700CLUB@yahoogroups.com, "teleronni" <telewinze@a...>
              wrote:
              > > > A CD V-700 modified to read 50 r/hr would be ideal(?). Open to
              > > > ieas/suggestions.
              > > >
              > > > Thanks
            • civildefenseinfo2002
              Mr. Telewinz, I think it might help everyone out if you mentioned why you want all of this equipment in the first place. My guess is its for some type of self
              Message 6 of 8 , Sep 5, 2005
              • 0 Attachment
                Mr. Telewinz,
                I think it might help everyone out if you mentioned why you want all
                of this equipment in the first place. My guess is its for some type
                of self protection type of thing, but I may be wrong.

                If it is, I think you'll find that your standard CD V-700, coupled
                with a CD V-715, 717, or 720, will be quite adequate for your
                monitoring needs. There is no need to get your 700 to go up to 50
                R/hr when a standard ion chamber meter will do that easily. You're
                just overlapping ranges otherwise.

                Again, if my assumption is correct, I suggest that if you haven't
                already, try and get some high-range dosimeters (CD V-742 is most
                common, but CD V-740 is just fine) and a dosimeter charger (CD V-750
                is most common). I might also suggest that there is a lot of
                commerical stuff out there, and on eBay, that is also excellent, but
                doesn't come with the yellow paint and CD sticker. I'd take a PRDM 82
                over a CDV anyday. Most importantly, all of the equipment you buy for
                this purpose either needs to be serviced and calibrated by the person
                you buy it from, or calibrated and serviced before you put it into
                service. The only place I know of that calibrates with a "hot" enough
                source is radmeters4u.com in Texas; the people who advertise on eBay
                you mentioned earlier.

                But, then again, most important thing to do is learn how to use them.
                Hang around here for a while, I have for a few years now, and you'll
                learn a lot. There's a bunch of reading materials on radiological
                monitoring available on the internet as well.

                I'm sure someyone here can tell you about the 5980; as I have no
                experience with it.

                CivilDefense2002
              • Geo
                ... TO ... FOR ... The QPL 5980 is a small thin wall tube for Gamma detection only. A modern part number would be LND 726. They both return 3.5 CPS per 1
                Message 7 of 8 , Sep 5, 2005
                • 0 Attachment
                  --- In CDV700CLUB@yahoogroups.com, "Ron" <telewinze@a...> wrote:
                  > Why not this "surplus" tube as a spare? Whats the ups and downs?
                  >
                  > PROBE 5980 THESE PROBES WERE USED IN THE SEVERAL MILITARY COUNTERS
                  TO
                  > EXTEND THE RANGE UP TO 500mR/hr. EASILY ADAPTABLE TO THE CDV-700
                  FOR
                  > RANGE EXTENSION.
                  >
                  > It's about $30 plus shipping.
                  >
                  >
                  The QPL 5980 is a small thin wall tube for Gamma detection only. A
                  modern part number would be LND 726.
                  They both return 3.5 CPS per 1 mR/H. Used as the high range tube in
                  many wide dynamic range Military Geiger's.

                  3.5 CPS = 210 CPM, therefore with a CDV700, max reading would be
                  30,000 ( max range switch) / 210 =142 mR/H.

                  A LENi with X2 range extender switch would double that.

                  Clearly the CDV-700 based units are biased for very low,
                  environmental and science project ranges.

                  Ludlum Model 3 has a 0-500,000 CPM range, so could read out all the
                  way to 2380 mR/H ( 2.38R/H)
                  still not WAR METER material, but better than the original Military
                  capabilities ( .5 R/H)

                  Most of the commercial high range tubes use 500V, while the Military
                  versions all use 700V. CDV-700's use 900V and are not normally
                  adjustable.

                  This is not a deal breaker though, because I have developed an in-
                  probe adaptor that works very well:
                  From the meter jack, series a 3.3M resistor with a 1.8M resistor,
                  then run that to the tube. At the junction of the two resistors,
                  place a Zener Diode string to ground, of a value to equal the tube's
                  requirement ( say 700V). Now from the connection point on the tube,
                  run a .01 uF, 2000V capacitor back to the jack connection. The
                  resistors and Zeners drop the 900V down to that required by the tube,
                  while the capacitor shunts that DC network, passing the pulse back to
                  the meter.

                  In most meters, this setup works perfectly, and is the basis for a
                  new probe I'm making, using those 480V Russian Pancakes!

                  One last thing, Lee Frank now advertises the 5980's for 19.99 USD on:

                  http://www.surplustuff.com/radiolog.html

                  Note, his 7616 is also small and has 10 CPS per 1 mR/H.

                  Have Fun

                  Geo
                • telewinze@aol.com
                  No, it s just toys and 60 s memorabilia. Thanks for the recommendation for a source.
                  Message 8 of 8 , Sep 5, 2005
                  • 0 Attachment
                    No, it's just toys and 60's memorabilia.  Thanks for the recommendation for a source.
                  Your message has been successfully submitted and would be delivered to recipients shortly.