đŸ Archived View for nytpu.com âș gemlog âș 2021-08-04.gmi captured on 2024-08-31 at 13:00:38. Gemini links have been rewritten to link to archived content
âŹ ïž Previous capture (2024-05-10)
-=-=-=-=-=-=-
A while ago I got a CD V-777-2 Radiation Detection Set, manufactured circa 1964. It's a kit that includes a CD V-715 radiation survey meter, six CD V-742 dosimeters, and a CD V-750 dosimeter charger. The main point of this post is just to provide my scans of the documentation (the only high-quality ones I've found), and some fun facts about it.
Fun fact, this set was FEMA's recommended and standardized radiation kit well into the â90s despite the fact that the U.S. Office of Civil Defense (OCD) that commissioned their manufacture was dissolved in the early â70s. My kit was updated with what I call a âquickstart guideâ in August 1976, around the time when the OCD was dissolved and FEMA took over, so I guess they started taking measures to at least update the instructions. My set has labels that said it was tested and calibrated in November 1996, so I assume it was still in use then. I bought it in 2017, so sometime between 1996 and 2017 is when they phased them out in lieu of some other kit.
On the whole the set is pretty useless to actually own because nothing in it is sensitive enough to detect radiation levels you'd encounter in real life. Still pretty fun to have though.
Miscellaneous materials:
It comes in a standard government-issue box with the old âCDâ OCD logo.
The most major component of the kit is the CD V-715 radiation survey meter. âDon't you mean a Geiger counter?â you might ask, and yet you'd be wrong! GeigerâMĂŒller tubes are relatively expensive to manufacture (despite being considered the cheap way to measure radiation), so for the kit that they're manufacturing millions of they instead opted for a simple ionization chamber, which is less sensitive.
While the meter looks cool, and is a very common prop in movies, it's not particularly useful for actual radiation detection due to its low sensitivity. It's only capable of sensing very high doses of radationâon the levels of a nuclear explosion, what it's designed to detectâso even with a large radiation calibration disc it doesn't give anything outside of the range the manual claims as an invalid reading.
Side view of the calibration knobs and internal components
Right to repair! Circuit diagram right in the case.
See also:
Wikipedia on ionization chambers
I find the dosimeters the most fascinating, despite being as equally useless for measuring radiation as the survey meter. I get probably 0.669 Roentgens per year in background radiation, which is on the high end of what most people get because of how high Colorado is in elevation and the relatively high radon concentration in most of Colorado. That is so little that it would probably be unnoticable on the dosimeters, which have a scale from 0â200.
However, I find them more fascinating because of how they work. They're quartz fiber dosimeters, and use the same basic ionization chamber principle that most radiation detectors use, but they're completely free of electronicsâthey don't have a battery or supercapacitor, all you do is put them on the charger to zero them out and then they'll just work. It works by charging an electrode, which repels the oppositely-charged quartz fiber away from it and onto the scale. Then, when radiation hits the ionization chamber, it will ionize it and those ions will discharge the electrode and the quartz fiber will move slightly closer, moving it along the scale, which is viewed with a mini self-contained microscope apparatus that takes up most of the dosimeter.
Manual for the dosimeters and dosimeter chargers. Once again contains detailed diagrams and a BOM.
The set of dosimeters and the charger
A dosimeter. This one's my favorite because it's colored different than the rest of them.
The side that you look through to view the reading
The charger, with the charging port cap off
The circuit, it's pretty simple. Also comes with an extra light bulb.
This circuit diagram is on the side of the case instead of being on the bottom for some reason
See also:
Wikipedia on quartz fiber dosimeters
This is a pretty low-effort post in terms of the actual writing I did, I mostly made this as an excuse to post the pictures and manual scans I made. Speaking of which, the licensing on those manuals:
âRadiological Dosimeter Charger Operating and Maintenance Instructionsâ and âRadiological Survey Meter Operating and Maintenance Instructionsâ were produced by the now-defunct Victoreen Instrument Company (VIC) under contract for the U.S. Office of Civil Defense (OCD). It is thought that the copyright was assigned by VIC to the OCD and that both instructional manuals are in the United States Public Domain. If they are not in the public domain, then they are orphaned works (i.e. they're still under copyright and you can't get permission to use them; but there's also no one around to sue you for using them either).
The copyright for the stuff I've produced on this page:
Copyright © 2021 nytpu - CC BY 4.0
â
contact via email: alex [at] nytpu.com
