Inside Old Geiger Counter

I would look for some 'date of manufacture' info on the components...or a date code in the serial number....

This is from the early 50's...

https://en.wikipedia.org/wiki/Civil_defense_Geiger_counters

Thanks for reply. Years ago I used to own the one you pictured. I looked on the inside of this current one and dont see a date. One number says 8073 which might be 8th week of 1973 but not sure.

I would try to find one like it on ebay...

Interesting. How do you know that it works?

I bought a Geiger Counter like the one below at an antique store that supposedly works, but I have not found anything that gives a reading. My understanding is that they are only sensitive to Gamma and if you get a reading, you should consider evacuation.

"Ion-chamber survey meters[edit]

These are instruments using the ionisation chamber principle.

If the meter on any of the ion chamber devices are observed to respond at all to a radiation source, evacuation of the area should be considered. No legally exempt source of gamma radiation would be expected to cause any visible deflection of the meter on its most sensitive setting, so it might be assumed that such a radiation field could be dangerous. Such a meter would not be expected to detect the presence of radiation except the very high levels that might be found in the event of a nuclear weapon detonation or a major release of radioactive material as from a nuclear reactor meltdown. The CD V ion chamber units are now all approaching 50 years old at a minimum and that they contain parts that are sensitive to moisture, so relatively frequent calibration and inspection by an accredited and properly equipped facility is required to ensure reliable and accurate function."

https://en.wikipedia.org/wiki/Civil_defense_Geiger_counters

I bought the one shown below a while back from Amazon. It plugs into the earphone jack and is only sensitive from the direction it is pointed.

It does react to a piece of uranium ore that I purchased from United Nuclear.

http://unitednuclear.com/

Yes that ion chamber one of yours is for after the bomb has gone off so its insensitive. Mine has a GM tube in it and will register if you show it anything more than 10 microsievert/hour. I had one of those phone ones and they are great but only go up to something like 100 microsievert/hour. Thanks for your reply.

I would suggest that the build time frame would be early 1950's. The molding technique of the capacitor would match what I find inside some similar vintage National Radio receivers that I have rebuilt. If it was constructed in the 1970's the capacitors would be epoxy dipped. A good resource I find is either old Farnell Electronics catalogs, or on this side of the pond, Allied Electronics catalogs.

Thanks very much for your post. I would not have though of epoxy dipping or catalogs. Its interesting the thing is so old.

My guess would be that it pre-dates 1968 when FR4 board material was introduced. Your board seems to be Bakelite or G10 or some similar material.

I see no evidence of printed circuit on either side, and the through holes do not seem to be plated through.

This "high value" item would have used leading edge technology (if it was for military use) and thus possibly pre-dates 1950 when single sided boards became available.

I suspect however that it post-dates 1945 as all the insulating material seems resin based as opposed to wood and other insulation used in the '30's.

Production dates on capacitors might provide "most recent" repair, or indicate year of manufacture. If there is a moving coil meter, then sometimes the technician would pencil the date onto the non-visible portion for traceability purposes.

Thanks, your post is full of interesting thoughts.

I have a Geiger counter outside in a rescue truck. Will have to get it to see if it is dated. Similar to the one Rixter shows. Never tried to put batteries in to see if it works. I'm pretty sure the dial scale is in mR.

I would expect background radiation to give a few ticks per minute. There is a threshold below which radiation is OK--it even helps the body.

Finally retrieved it. What I have is a Tracerlab Model SU-14 GM Survey Meter made 1955-1960. Serial number 402. The readings go from 0 to 25 mR/hr. There are 3 scales to give max scale readings of .25, 2.5, and 25 mR/hr. The latter is 50000 counts per minute. It has a jack for headphones which are the only audio output. There are no batteries with it, so I have never tried; 3 of them are special (to me) 45 volt batteries, so I'll probably never try, because I have no use to justify the cost of those batteries. It also needs (4) D cells.

Looks to be in pristine condition. The style of the transistors, components, etc., would give the range of possible dates. Presumeably, there's no make or model number evident on it?...

Maybe, you could take it to a pawn shop, or to a used military equipment store, or a relic re-seller, that could point you to an authority on the subject?...