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

Andreas Schuldei andreas+rrdtool at schuldei.org
Fri Mar 10 14:46:27 CET 2017

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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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