[rrd-users] Quantisation issues - how do i get the math right?

[Tobias Oetiker]

Hi Andreas 

ah it is a counter ... then you use COUNTER ... I thought you had something detecting events ... then you could use update to 'load' and event into the rrd. 

cheers 
tobi 

----- On Mar 10, 2017, at 4:37 PM, Andreas Schuldei <andreas at schuldei.org> wrote: 

> I changed that and am puzzled.
> how do i deal with the huge offset? In that setup, the value the device returns
> is ~8000, and its a 64bit counter...

> in an other thread ( [
> https://lists.oetiker.ch/pipermail/rrd-users/2014-September/020015.html |
> https://lists.oetiker.ch/pipermail/rrd-users/2014-September/020015.html ] )
> that seems to deal with a similar issue, someone recommend:

> "Alternatively, you could use Absolute and reset the counter each time - then
> you don't need to worry about storing the total."

> I can not reset the counter in the device. Or is that some rrdtool counter that
> i can reset with some clever CDEF magic?

> And how will the data, which "absolute" would give me, be usable in my case?
> from the documentation ( [
> https://oss.oetiker.ch/rrdtool/tut/rrd-beginners.en.html |
> https://oss.oetiker.ch/rrdtool/tut/rrd-beginners.en.html ] ) i understand i
> would get an slowly ascending staircase. But in what way can i use that to
> emulate my incoming power? ever increasing power from my solar panels would be
> awesome, but that is not what I experienced before using rrdtool :-)

> On Fri, Mar 10, 2017 at 3:10 PM Tobias Oetiker < [ mailto:tobi at oetiker.ch |
> tobi at oetiker.ch ] > wrote:

>> if you have 'pulses' use the ABSOLUTE DS type ...

>> and the multiply the result by whatever a pulse is worth

>> cheers
>> tobi

>> ----- On Mar 10, 2017, at 2:46 PM, Andreas Schuldei < [
>> mailto:andreas%2Brrdtool at schuldei.org | andreas+rrdtool at schuldei.org ] > wrote:

>>> This is a graph i get with my current intake of sun and my setup, consisting of
>>> thermo sensors on in- and outgoing water pipes, as well as a water meter,
>>> emitting S0 impulses, indicating that 10l of fluid were pumped.
>>> My Issue is with dealing with the impulses in a sensible way. The interval of
>>> these impulses varies, depending on the sun intake.

>>> currently my CDEF for the solar power is
>>> d,c,-,a,*,10,*,4.190,*
>>> where c and d are my temperatures, and a is my counter, indicating 10 liters.
>>> (4.190 is the specific heat constant of water.)

>>> Now what is calculated by that CDEF is not really the solar power, its the
>>> momentary value, only, calculated for the duration of the impulse, which is the
>>> width of my sampling rate (which is 10sec). it would have been more accurate to
>>> take the time between the impulses and calculate the incoming energy during
>>> that period, divided by the duration of that time and graph that for the
>>> previous (or following) interval.

>>> How can I do that?

>>> _______________________________________________
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>> --
>> Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland
>> [ http://www.oetiker.ch/ | www.oetiker.ch ] [ mailto:tobi at oetiker.ch |
>> tobi at oetiker.ch ] [ tel:+41%2062%20775%2099%2002 | +41 62 775 9902 ]

-- 
Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland 
www.oetiker.ch tobi at oetiker.ch +41 62 775 9902 
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