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.

[AlphaTea]

I have to admit, I'm a flaming dumbass because I have no idea what any of the above means.
"Pardon me stewardess, I speak Nerd" (second time I wrote that, Im gonna have to change my sig line...)
If you want a cheap radiation detector for your preps, these are adequate without breaking the bank. You just need to understand the limitations of the detector(s).

BTW, I dont know about the 'flaming' part, but you are not a 'dumbass'. After all you did get this site rolling.
This is why I am here. We can each offer up our areas of expertise to fill in somebody elses blanks. I watch more than I post and I for one have gotten a lot from you folks than you will ever know. I will try to jump in whenever I see something I know about.

[AlphaTea]

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.
I was having a little trouble deciphering what you actually did here.
When you are calibrating, or checking the calibration, you cant just put the instrument in a radiation field and check all the ranges with just one doserate. Each range has its own cal pot. To get a source with enough activity to check the high scale, you would need a source that emmited 2-2.5R/hr @ ~20 inches from the source. You aint gonna find that.
That high of a doserate will have to be in a well type calibrator or a box calibrator (like a safe).
Most of the range type calibrators I have used usually had a max (usable) doserate of about 200mR/hr. You could then use a DR(r)^2 calculation to get the lower doserates.
My advice?
Pony up the bucks and have KI4U do it for you.
If anybody is interested I can show you how to make your own check source for the lower range to at least check the operability of your meter.

[The Stig]

After all you did get this site rolling.


Actually RedJohn gets the credit for that but thank you for the kind words.

[Grumpy Old Man]

I was having a little trouble deciphering what you actually did here.
When you are calibrating, or checking the calibration, you cant just put the instrument in a radiation field and check all the ranges with just one doserate. Each range has its own cal pot. To get a source with enough activity to check the high scale, you would need a source that emmited 2-2.5R/hr @ ~20 inches from the source. You aint gonna find that.
That high of a doserate will have to be in a well type calibrator or a box calibrator (like a safe).
Most of the range type calibrators I have used usually had a max (usable) doserate of about 200mR/hr. You could then use a DR(r)^2 calculation to get the lower doserates.
My advice?
Pony up the bucks and have KI4U do it for you.
If anybody is interested I can show you how to make your own check source for the lower range to at least check the operability of your meter.

What I was doing was using the cesium source in the backscatter position just to see if the instrument was functioning. It wasn't meant to try and calibrate, just to see how it was working. That source isn't very strong but it can give a good idea of what needs to be done. That was where the detachable feature was useful. And yeah $92 is cheap at KI4U. It beats $150+ for my nukalert (which also has a battery shelf life).

[LUNCHBOX]

I'm with Stig on this, I heard gamma and thought of the Hulk. It must be late. Really though, you guys sound like your on your game. I hope we don't need any of those cause I'm hit if we did.

[AlphaTea]

What I was doing was using the cesium source in the backscatter position just to see if the instrument was functioning. It wasn't meant to try and calibrate, just to see how it was working. That source isn't very strong but it can give a good idea of what needs to be done. That was where the detachable feature was useful. And yeah $92 is cheap at KI4U. It beats $150+ for my nukalert (which also has a battery shelf life).
Cool. as long as you understand you are doing a response check, not in any way should this be used to adjust the meter. Any adjustments should be done in a controlled environment where the field strength, backscatter and geometry effects have been accounted for.
I have a couple of those Nukalerts. Matter of fact I have one of the prototypes. Accuracy on them is actually pretty decent across the range once they settle in.
Wifey used to keep one in her purse but she stopped because the chirping was driving her nuts. Seems they dont like quick temperature changes and during the winter her in NY her purse could change temps quickly. Getting it cold makes it think there is a radiation field nearby.
Anyway NukAlert.com has a battery/calibration deal where you get a new case (they get scratched up after a while), battery and desiccant change and a new calibration for $35.
Mine are better than 10 years old and still chirp. I occasionally check them at work :)

[Grumpy Old Man]

A response check is what I thought I was describing. I have nothing here to calibrate with-no sources, so that is out of the question. As I said previously, I'll spend the $92 at KI4U for calibration.

On a separate note, KI4U is now marketing a dosimeter sticker that is relatively inexpensive. I may pick up some of them as well. The dealer out here is Cal-Quake Inland Empire. The are about $5 each so that is a pretty cheap way to get a dosimeter. They do have a minimum order of 5, so that could easily cover a typical small family today.

[bacpacker]

Alpha, Do you all use a pulser for a part of your calibrations? We use A Ludlum Model 500, for a lot of our cal's at work. for the linearity portions of the cal's.
Did you and grumpy get your nukalerts at KI4U? I've thought about gettin a couple for me and the wife.

[Twitchy]

RedJohn should consider becoming a distributor of KI4U... Money to be made!

[AlphaTea]

Alpha, Do you all use a pulser for a part of your calibrations? We use A Ludlum Model 500, for a lot of our cal's at work. for the linearity portions of the cal's.
Did you and grumpy get your nukalerts at KI4U? I've thought about gettin a couple for me and the wife.
I moved out of the Calibration Lab a few years ago, but if I remember correctly it was a Ludlum model 500A Pulser. We would use it for most any GM or BF3 type detector and some PM detectors for ranges we could not get to with a source. Of course this would not work on an Ion chamber as those are just glorified ampmeters.
When I worked in the Cal Lab, we bought a few of the NukAlerts from KI4U to evaluate for our emergency response teams. While they are pretty neat and the price is not too high, they did not have the precision we were looking for. Our management decided to spend more for something with a lot more features. Since the NukAlerts were "orphan" instruments that we were not going to use, they were up for grabs. I got three and gave one away.

[Grumpy Old Man]

BP, I gave the place in my previous post where I got mine (nukalert). KI4U typically uses distributors to sell such items. When you go to their website they will have the distributors listed at the bottom of the page. Click the links to find the one closest to you.

[bacpacker]

I missed that Grumpy, thanks.
Alpha that is pretty much the same set up we use for cal's. Just curious if you guys did the same or had other gear.

[AlphaTea]

We have a Shepherd model 89 box calibrator and a Table mounted beam calibrator that I think was a Model 28. For neutron Cals we have a PuBe source.