717 Radiation Detector

[Grumpy Old Man]

Just got in my new order from Sportsman's Guide which included a 90 pill bottle of 32.5 mg KI. While I was checking out when ordering this product they did the usual thing of "people who bought this also bought ......". Lo and behold there was a 717 CD Radiation detector for $99 (cheaper if you belong to the Buyer's Club). So I picked one up to fill that big hole in my preps when it comes to radiation. Basically on this unit the geiger-mueller tube is completely enclosed in the base of the machine. It runs on one D cell battery which means I'll have to buy a new rechargeable battery set-up as the one I have is for AAA & AA batteries. All in all I'm very pleased with this acquisition.

BTW for our purposes 1 Roentgen (R) is approximately equal to 1 Rem (Roentgen equivalent man). I won't go into the conversions of Grays and Sieferts. I stick to what I learned originally and screw the SI units!

[Twitchy]

IF that is calibrated I may just head over there myself...

[Grumpy Old Man]

The meters very seldom drift out of calibration. This was NIB as the electronics are up to date. When I was an RSO I was sent to Troxler school in Arlington TX to learn repair and calibration of nuclear densometers and detection devices. The densometers were the only ones that really drifted owing to half-life of the Cesium source (~30 years). If you know your typical background radiation you can check that way. I have friends who are still dirt cops so I'll check the calibration by using one of their densometers.

[Twitchy]

The meters very seldom drift out of calibration. This was NIB as the electronics are up to date. When I was an RSO I was sent to Troxler school in Arlington TX to learn repair and calibration of nuclear densometers and detection devices. The densometers were the only ones that really drifted owing to half-life of the Cesium source (~30 years). If you know your typical background radiation you can check that way. I have friends who are still dirt cops so I'll check the calibration by using one of their densometers.

You could make a quick buck calibrating machines...

[bacpacker]

It's not a bad job. I did it for a few years.
Grumpy, I'm not familiar with the 717, what all does it measure? I've been considering a surplus Bicron and get an Alpha and beta-gamma probe, just for rough counting. Easy to work on and pretty simple to use for general survey's

[AlphaTea]

I too have a little experience with the 717 and some of its cousins.
For the most part, you get what you pay for.
I have seen folks buy these things expecting more than they got.
Stated accuracy is + 20%.
I worked in the RP Calibration Lab for about 16 years and I would try to get a decent Calibration for friends (on my own time). It was rare to get one that was able to get the 20%.
Generally we would adjust it at 50% full scale and check it at 20% and 80% of scale. Not always linear, but hey, it was usable.
You have to remember that these were made back in the early '60s. The technology is VERY rugged and reliable.
They were made for the average Joe to use, not professionals who might need very precise readings.
That being said i have a few suggestions:
Dont use rechargeable batteries. Voltage varies too much. They were designed for the old style carbon batteries, but alkaline will be just fine.
Do not store it with the battery installed. Too many people forget to turn it off when done which causes dead batteries which leak. Also if stored in a hot area (car trunk, attic etc) the battery my not fare well. Remove the battery after use.
The 717 has a remote use feature (case separates) try to minimize using this. While the cable was usually OK the connectors were sometimes weak.
Being an Ion Chamber type detector, it has limitations. Temperature and barometric pressure will effect the reading. Usually calibrated to 22C and 760mm Hg (room temp at sea level). Every 1000ft in elevation increase will cause about a 5% increase in the reading. Hotter temp makes readings higher too.
It is imperative that you keep the inside of the meter dry. VERY dry.
Buy a Photon Micro-light or equivalent and tape it to the handle. I usually used shrink tube. Meter is no good in the dark or low light if you cant read it.
YMMV

[Grumpy Old Man]

Ditto what AlphaTea said. I checked this last night against my buddy's troxler case which has a TI of 0.3. The lower end of the scale (0.01X) is way out of whack, at higher scales (1X and 10X) it was OK, but just. BTW I was checking the Cesium source. The lower end of the scale is problematical. As has been pointed out above this is not a super fine instrument. KI4U will calibrate for $92, which is more than I have in the instrument, so I will probably do that. But I still don't expect good results on the lower end. The CDV 717 was designed primarily for surveys on the high end after a nuclear event. That being said, this will be used to get an initial reading which I can then plug into TOM's spreadsheet to calculate decay rates and when it will be safe to go out.

Or, I'll get blown up in the event and you guys can divvy up my remaining preps.

ETA: This is for gamma radiation.

[bacpacker]

Good info guys. I worked in a cal lab for 2 years and for 10 years in a plant manufacturing gamma spectroscopy detector and electronics. They were very specific instruments.

There is some older stuff being taken out of service for new equipment that will probably be salvaged at some point. I'm tryin to keep an eye out for when that happens.A lot of the old gear gets sent over seas to third world cuntries, so I don't know if anything worthwhile will ever come up for a bid.

[Grumpy Old Man]

I've seen one deal recently for CDV 715, 717 and 720 for ~$70 for all three. I think KI4U's dosimeters are the bomb, but they are a little pricey. (Sorry for the bad pun). These things are like a 1 minute Transit versus a total Station in surveying-you can accomplish the task, you just have to have a feel for the accuracy of your instrument. I'm going to e-mail Tired Old Man and ask if I can post his spreadsheet here. He's a good guy and he and Jerry Young are pretty tight, so we might even get him to join here.

[The Stig]

I have to admit, I'm a flaming dumbass because I have no idea what any of the above means.