[rrd-users] how to calculate the sum of a DS
Alex van den Bogaerdt
alex at vandenbogaerdt.nl
Fri Jul 5 13:09:50 CEST 2013
----- Original Message -----
From: "stefan" <Stefan.Bruder at gmx.net>
To: <rrd-users at lists.oetiker.ch>
Sent: Friday, July 05, 2013 9:31 AM
Subject: Re: [rrd-users] how to calculate the sum of a DS
> Hi Alex,
> thank you for your explanation, but now I am little more confused.
> my PV controller gives me the power created ( example 400Watt) each 10
> so I have 400W/10s.
No. It's not 40W every second. It's 400 (on average) Joules every second
during 10 seconds.
That is: if your device indeed does report in Watt.
Also possible (and more likely) is that your device reports energy
delivered, for instance in Wh.
If you confuse W with Wh, you won't get correct numbers unless by chance.
Make sure you understand the difference, and why it is watt multiplied by
hour, not divided by hour.
> For my understanding I should take the sum of all value (where watt >0)
Why the ">0" restriction?
We'll get to the rest as soon as you figured out exactly what is reported:
energy or power.
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