(IF you wish to see detailed features of the Radex RD1212 click here.)
(To see my post on what comes in the package & my pictures from the day it arrived click here )
When
I first got my Radex RD1212,I did not understand that radiation is not stable. What I
mean is that it fluctuates minute by minute when you are taking readings in the
rage of .01 uSv/hr (1/100th of a micro serverts/hour).
A sudden reading fluctuation up to 0.30 uSv/hr for one reading during the first two days of owning the device caused some doubts. in general the highest reading for that area is 0.22 is uSv/hr.
After contacting to 2 other more experienced users I learned that such a fluctuation is quite normal, and could be consider small in some parts of the world. One of the contacts was at first thinking that I got a spike form natural minerals in that area. He stated that if I had high levels of natural thorium/uranium/potassium, that can make the readings jump wildly. He suggested I test in multiple locations for an extended time.
I did as he suggested. I tested out the device by taking extended readings at
three locations. I included the location that caused me to doubt the
reliability of the device as location #3. I think with only 3 locations I was
able to determine the device is stable. Let me know if you disagree.
The first location was stable and in a narrow range,
completely opposite from what I expected. I was able to duplicate the same
results 2 more times. I failed to record the average for December 12, but 0.09 uSv/h is a safe bet.
Location #1 - 41.045302,-85.264529 (Yellow
Apartments)
December 11,
2013 - 180 reads, Minimum 0.06, Max 0.14, Avg 0.09
December 12,
2013 - 140 reads, Minimum 0.06, Max 0.14, Avg ?.??
December 15,
2013 - 180 reads, Minimum 0.06, Max 0.13, Avg 0.08
(Readings are
in uSv/h)
For a full
print out of results for each test click here:
I even have
a single test of readings about 1 mile from location #1 that is very similar:
December 24, 2013 - 180 reads, minimum 0.06,
Max 0.14, average 0.09
Location #2 had a lower lowest reading that was 0.01 uSv/h below the lowest reading of Location #1. It had a highest reading that was
0.02 uSv/h higher than the highest reading of location #1.
Once again a rather stable set of readings.
Location #2 - 41.015069,-85.151838 (Willow Creek)
December 11,
2013 - 180 reads, Minimum 0.05, Max 0.14, Avg 0.10
December 13,
2013 - 180 reads, Minimum 0.07, Max 0.16, Avg 0.10
December 22,
2013 - 180 reads, Minimum 0.06, Max 0.15, Avg 0.09
(Readings are in uSv/h)
For a full
print out of results for each test click here:
Location #3 is by far the most interesting. You will note that on December 9, 2013 I got
a high reading or 0.030 uSv/h and that is why I contacted you
for your opinion. You will note
the even without the December 09 reading this location has a noticeably higher
and wider range.
Location #3 - 41.098952,-85.11396 (Buena Vista Drive)
December 08,
2013 - 18 reads, Minimum 0.09, Max 0.22,
Avg 0.12
December 09,
2013 - 39 Reads, Minimum 0.08, max 0.30, Avg 0.14
December 11,
2013 - 65 reads, Minimum 0.09, Max 0.19, Avg 0.13
December 12,
2013 - 118 reads, Minimum 0.08, Max 0.22, Avg 0.13
December 13,
2013 - 153 reads, Minimum 0.08, Max 0.20, Avg 0.13
December 16,
2013 - 160 reads, Minimum 0.07, max 0.19, avg
0.12
(Readings are in uSv/h)
I had one
other instance where I got a spike up to 0.34 uSv/h at location #3. I do not have that data as the device was not
recoding it. That makes Location #3 the only location where I could duplicate
such a spike over 0.22 uSv/h.
I think that
the fact I was able to consistently get stable data in a narrower and lower range
at two different locations shows that the erratic readings I get on the device
are a result of something in the environment of Location #3.
In over 1700 readings I was not able to duplicate the
sudden spike up to 0.30
uSv/h at any other location than
the one that shows the widest and highest readings, except for one time when I
was not recording data and I got a spike up to 0.34 \ in that same location.
Also I was unable to get a reading of over 0.16
uSv/h at any other
location.
I will finish this post with a resonse from one of the other Geiger counter experts:
https://www.youtube.com/watch?v=0tOARezivxo
Interesting!
I would say that your hypothesis that the readings are environmental
is correct. I took all three sets of numbers and ran them through a
spread sheet with some math. Here is what I found:
Samples 1
Avg 0.0897222222
StdDiv 0.0180139783
Max n sigma 2.7910424318
Samples 2
Avg 0.0988703704
StdDiv 0.0170021785
Max n sigma 3.5953998248
Samples 3
Avg 0.1250699301
StdDiv 0.0256849156
Max n sigma 6.8106150984
Note:
1 & 2 did have at least one count each exceeding the normal
rule-of-thumb 2 standard deviations, meaning that these were likely
events above and beyond standard background. 3 had a quite a jump.
Without
more sophisticated gear, we will likely never know the source, but if I
had to guess, I would suspect sample 3 detected a muon shower or
something like that. Environmental contamination is often pretty stable
(the readings). Those jumps are likely cosmic in origin.
Still, a
6.81 standard deviations from the norm jump is higher than anything I
have detected (in terms of a spike, not the actual count). Last time I
got something that high it was from a solar event. When such things
occur, they and correlate them with solar activity.
if you have a spread sheet software, try this:
If Column A has the counts, then for each x in A,
Column B = if( A(x) - AVERAGE(A(0):A(n)) / STDEV(A(0)>2; A(x) - AVERAGE(A(0):A(n)) / STDEV(A(0); 0 )
Change A(x) to the cell number (e.g. A53). A(0) means first cell and A(n) means last cell.
or, if this is easier:
Number of standard deviations = count - Average / Standard Div.
