Personal Geiger counter, radiation measurements in the city of Goes, The Netherlands. Note: I'm not using officially calibrated equipment, so don't draw any conclusions. Just use the graphs for comparing variations over time.
About this blog
So I got the urge to be able to detect and measure radiation by my own, especially since I live within a 15km radius from the NPP of Borssele and a 30km radius from the four reactors of Doel NPP, Belgium.
Browsing the internet, I found some relatively cheap ex-army radiation detectors at an army-dump shop. One of them appeared to be suitable to even detect the (usually low) background radiation levels: A Frieseke & Hoepfner FH40T Geiger counter (fitted with a FHZ76V energy-compensated geiger-mueller tube), sensitive to γ (gamma) radiation and β (beta) radiation over 0.25MeV.The FHZ76V tube actually contains a Valvo 18550 tube, which is equivalent to Centronics ZP1320, Mullard Mx164 and LND-713 (found in this Probe Selection Guide and here)
The specs of the ZP1320 tube claim a sensitivity of 9cps/mR/h for Cs-137 (540cpm/mR/h). For 'normal' background (0.025-0.045mR/h) this results in a counting rate of approx.10-20cpm.. Where I live, I measure values varying between 4cpm up to 25cpm. This variation is caused by the randomness of the decay of radioactive elements.
Note:
1 R = 8.77 mGy
1 Gy = 115 R
For sake of simplicity, in our calculations we simply use 1R = 10mGy and 1Gy= 100R. And so is 10µR = 0.1µSv.
This approximation is good enough for this experiment.
There are 3 types of radiation:
α (alpha) decay is helium nucli being released, (beta) decay is electrons (β-) or positrons (β+) and γ (gamma) decay is electromagnetic radiation (like X-rays).
This Geiger-Mueller tube is only sensitive to β and γ radiation. The calibration is only correct for the γ radiation (662keV) emitted from Cs-137 .
I am now on the lookout for a device that can detect alpha radiation too. But the current situation in Fukushima has stirred up the market (crazy prices, run out of stock) for detection devices so I better wait until better times.
Saturday, April 23, 2011
Pictures of my Geiger counter - computer interface
The FH40T Geiger Counter, with its speaker-output connected to a breadboard with PIC16F628A microcontroller and LCD and RS232 output.
The microcontroller counts the pulses from the geigercounter during a fixed interval (111.11seconds) and converts them to a value in mRem/h. The value is displayed on the LCD and sent on the RS232 port connected to a PC, which also supplies 5V DC to all circuits
On the left is a more detailed photo of the experimental breadboard setup of the Pulse counter with PIC16F628A processor / LCD / RS232.
Thank you for the pictures and the description. Very nice work!
ReplyDeletePeople may be curious about the circuit diagram and the µC sourcecode, but that may cause you a lot of work.
Maybe a link to the datasheet of the geiger-tube will be much appreciated by your readers.
Greetings from Germany,
katze
hi katze,
ReplyDeletethank you for the comment. I'll see what i can do to fulfill your request. stay tuned.
regards, RadGoes
Hi,
ReplyDeleteWe did something very similar here in Geneva. Look at http://www.pachube.com/feeds/21511
Best regards,
Jacques
Thanks for leaving a comment, Jacques.
ReplyDeleteIt's nice to see there are more similar activities.
Have been able to observe any noticeable changes in CPM, caused by the
Fukushima Nuclear disaster ?
Best regards, RG