<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=us-ascii"><meta name=Generator content="Microsoft Word 14 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";
mso-fareast-language:EN-US;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal;
font-family:"Calibri","sans-serif";
color:windowtext;}
span.EmailStyle18
{mso-style-type:personal-reply;
font-family:"Calibri","sans-serif";
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:72.0pt 72.0pt 72.0pt 72.0pt;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body lang=EN-AU link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='color:#1F497D'>Hi rrdtool users,<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>I just sent this to the list, but it is waiting for the moderator to approve as I incorrectly thought I was a member. That was lucky! I just noticed that I was mistaken about the size of the results I was getting. They are too small, not too large. I was so used to seen +e01, that I didn’t notice the change to –e01 in my latest experiments. So it seems the five minute counts are not being accumulated by rrdtool, but averaged as raw values.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>However, my main question remains, what is the correct way to update a count like this? If I change to datasource type COUNTER, and accumulate the counts myself, will it be ok to update every 5 seconds? Is that recommended, or is there a better way?<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'> Thanks, Alan F. <o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";mso-fareast-language:EN-AU'><br><b>Subject:</b> Capturing a noisy count variable (Geiger counter)<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Hi rrdtool users,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I am trying to generate some graphs of background radiation counts per minute from a Geiger counter. I thought to use rrdtool and learn a bit about the tool as the same time.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>An issue I have is to understand how the interpolation works. I originally used a datasource of type GAUGE, and then I found the database was not storing integral values. That led to learning about how rrdtool captures data. I understood that some form of interpolation was being done, but I found that even when I timed my captures close to the datasource time period (i.e. within a few seconds), I was still getting significant averaging that I could not understand (counts were occasionally well off integral values). I then tried using a MAX RRA for the primary archive and that also did not seem to help. For an example of the effect, see <a href="http://www.chankly.com/geiger_underconstruction/cpm.html">http://www.chankly.com/geiger_underconstruction/cpm.html</a><o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>If my graphs contain non integral counts for one minute intervals, then I am going to need to explain why.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I started reading some forums, I decided to try using and ABSOLUTE datasource type since that seemed to be more appropriate. However it did not seem to change much. Then I considered that since I was actually getting counts every second from my Geiger counter, and accumulating them for one minute in my scripts, I could instead update the database more often than the step interval. That way, I may not expect to get integral counts, but they should accurately reflect the “counts per minute” as a gauge.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>So I have implemented an update every 5 seconds, and I am getting very strange results, way too large values. Is it reasonable to update more often than the step interval?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>If not, then what is a recommended way to accurately capture these counts? What I really want to be sure of is that the integral of the displayed graph should accurately reflect the count for any chosen interval, i.e. avoiding any systemic error. The longer I capture the more accurate my averages should be. The backround CPM is quite stable for long intervals, and I want to look for trends related to sun activity, seasons etc. So I need to be confident the long timeframe averages reported by rrdtool are correct.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Here is an extract of the db, these values are much higher than they should be:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>$ rrdtool fetch /var/apps/geiger/geiger.rrd AVERAGE | tail -20<o:p></o:p></p><p class=MsoNormal>1365867360: 3.5410117577e-01<o:p></o:p></p><p class=MsoNormal>1365867420: 3.1358877058e-01<o:p></o:p></p><p class=MsoNormal>1365867480: 3.7223225156e-01<o:p></o:p></p><p class=MsoNormal>1365867540: 3.2656777052e-01<o:p></o:p></p><p class=MsoNormal>1365867600: 4.9940582148e-01<o:p></o:p></p><p class=MsoNormal>1365867660: 3.9069307467e-01<o:p></o:p></p><p class=MsoNormal>1365867720: 2.6239790085e-01<o:p></o:p></p><p class=MsoNormal>1365867780: 4.2388944703e-01<o:p></o:p></p><p class=MsoNormal>1365867840: 5.0398253216e-01<o:p></o:p></p><p class=MsoNormal>1365867900: 3.2639678663e-01<o:p></o:p></p><p class=MsoNormal>1365867960: 4.4485142178e-01<o:p></o:p></p><p class=MsoNormal>1365868020: 2.9939793410e-01<o:p></o:p></p><p class=MsoNormal>1365868080: 3.6032755674e-01<o:p></o:p></p><p class=MsoNormal>1365868140: 2.8273224979e-01<o:p></o:p></p><p class=MsoNormal>1365868200: 2.4941790093e-01<o:p></o:p></p><p class=MsoNormal>1365868260: 2.7300076071e-01<o:p></o:p></p><p class=MsoNormal>1365868320: 4.3303353491e-01<o:p></o:p></p><p class=MsoNormal>1365868380: 2.3303745712e-01<o:p></o:p></p><p class=MsoNormal>1365868440: 3.0171077034e-01<o:p></o:p></p><p class=MsoNormal>1365868500: -nan<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Here is the perl code I am using to update the db, in a loop every 5 seconds:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal> my $timestamp = `date +%s`;<o:p></o:p></p><p class=MsoNormal> chomp $timestamp;<o:p></o:p></p><p class=MsoNormal> print LOG "time=$timestamp, returned count = $count \n";<o:p></o:p></p><p class=MsoNormal> my $result = `rrdtool updatev /var/apps/geiger/geiger.rrd N:$count`;<o:p></o:p></p><p class=MsoNormal> print LOG "updatev returned: $result";<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>And here is a section of the log, and it is clearly evident something is wrong with the counts (the average CPM is around 21).<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365866940, returned count = 1<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>[1365866940]RRA[AVERAGE][1]DS[geiger] = 2.4979012130e-01<o:p></o:p></p><p class=MsoNormal>time=1365866945, returned count = 2<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365866950, returned count = 3<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365866955, returned count = 5<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365866960, returned count = 0<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365866965, returned count = 2<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365866970, returned count = 1<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365866975, returned count = 7<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365866980, returned count = 6<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365866985, returned count = 3<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365866990, returned count = 1<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365866995, returned count = 3<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867000, returned count = 1<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>[1365867000]RRA[AVERAGE][1]DS[geiger] = 5.6636103674e-01<o:p></o:p></p><p class=MsoNormal>time=1365867005, returned count = 0<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867010, returned count = 0<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867015, returned count = 3<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867020, returned count = 2<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>saving incomplete line <CPS, 1, ><o:p></o:p></p><p class=MsoNormal>time=1365867025, returned count = 1<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867030, returned count = 1<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867035, returned count = 2<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867040, returned count = 1<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867045, returned count = 5<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867050, returned count = 2<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867055, returned count = 2<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867060, returned count = 3<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>[1365867060]RRA[AVERAGE][1]DS[geiger] = 3.6438774029e-01<o:p></o:p></p><p class=MsoNormal>time=1365867065, returned count = 1<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867070, returned count = 1<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867075, returned count = 4<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867080, returned count = 1<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867085, returned count = 1<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867090, returned count = 1<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867095, returned count = 0<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867100, returned count = 1<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867105, returned count = 1<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867110, returned count = 1<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867115, returned count = 1<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>time=1365867120, returned count = 0<o:p></o:p></p><p class=MsoNormal>updatev returned: return_value = 0<o:p></o:p></p><p class=MsoNormal>[1365867120]RRA[AVERAGE][1]DS[geiger] = 2.1964405340e-01<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>The db definition is as follows:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>rrdtool create geiger.rrd -s 60 DS:geiger:ABSOLUTE:100:0:U \<o:p></o:p></p><p class=MsoNormal>RRA:AVERAGE:0.5:1:50000 \<o:p></o:p></p><p class=MsoNormal>RRA:MIN:0.5:60:8800 \<o:p></o:p></p><p class=MsoNormal>RRA:MAX:0.5:60:8800 \<o:p></o:p></p><p class=MsoNormal>RRA:AVERAGE:0.5:60:8800 \<o:p></o:p></p><p class=MsoNormal>RRA:MIN:0.5:1440:7305 \<o:p></o:p></p><p class=MsoNormal>RRA:MAX:0.5:1440:7305 \<o:p></o:p></p><p class=MsoNormal>RRA:AVERAGE:0.5:1440:7305<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal> Alan F.<o:p></o:p></p></div></body></html>