[rrd-users] Dynamic Steps

Alex van den Bogaerdt alex at vandenbogaerdt.nl
Wed Apr 17 20:00:49 CEST 2013

>> Try the ABSOLUTE counter type, feeding 3600 (for Wh) or 3600000 (for kWh)
>> every time you get a signal.

> I'm not sure that I get this right. Do you mean to write 3600 every time i 
> get a signal, or to have 3600 steps?

One 'tick' of your device is equal to 3600 Joules, which you consumed during 
the time between the previous tick and the current tick.
That is why you use ABSOLUTE, see the documentation on what this does.

For example, you get one tick after 10 seconds. That means you used 3600 
joules in 10 seconds (which is an average of 360W during 10 seconds). When 
you update your database, RRDtool computes a rate of 360 and works with that 
during the normalization and consolidation phases.

See my site ( http://rrdtool.vandenbogaerdt.nl/ ) for some information.

Your step size is important when considering how much detail you want/need. 
You could set it to 1.
Your heartbeat value should be large enough to not miss updates that happen 
to be far apart. If all consumers in the house are off, almost no power is 
used. Your measuring device itself is the only one. Compute how long it 
takes for it to consume one Wh, double that time just to be sure, and set 
that as your heartbeat value.

> I've been playing around and got a working setup by using the GAUGE 
> counter type and for the RRA I used the LAST aggregate function. It gives 
> me a graph that seems to be right.

That could be. It could seem right, or it could even be right. What I am 
trying to tell you is that RRDtool can do this task of computing the power 
consumption, you do not need to do that yourself.

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