# [rrd-users] Summarize minute values into hourly values

JoeSpam8 JoeSpam8 at gmail.com
Fri Feb 18 20:55:59 CET 2011

```>OK, I think part of your problem is that you don't appear to
>understand the units in use - or you are just sloppy in your use of
>units. Either way, that is a recipe for problems.

>I assume you mean, your power meter will show you between 20 and 60
>watts. Watts/minute doesn't make sense as watts is a unit of power
>(energy/time) so dividing by time again would give you energy/time^2
>or rate of change of power.

OK, I think we talk about the same but let me clarify.

I have a pulse counter that counts the LED flashes on my households power
meter. Every pulse is a watt used. I get the data from the pulse counter
once every minute and I do my own calculation and I find out how many watts
have been used since last time I read the pulse counter. This is normally
something between 20 and 60 pulses (watts) every minute. So... fx. 40
watt/min.

>If your meter tells you an instantaneous rate (such as 60W) then you
>should use type gauge - and update frequently so as to capture
>changes in the value.

Yup, exactly.

>If your meter tells you accumulated energy (eg kWh) then you should
>use type counter - and it's not as critical to update so often since
>the meter is capturing all those fluctuations and adding up the total.

Nope - I am getting the watts - I have a GAUGE defined, not a COUNTER.

>Now, having got an rrd database which holds power usage in watts, you
>can get values out. You can graph the data, and scale it as you wish
>- eg divide by 1000 if you want to display kW. Also, you can work out
>totals - so if you want the energy used over the last hour, then you
>can get the average power over the last hour, multiply by 3600 to get
>energy used in Joules (Ws), divide by 3600 to get Wh, and divide by
>another 1000 to get kWh.

> Eg, if you were running a 60W light bulb,
>then you'd have 60 stored in the database. 60*3600 = 216,000 Ws,
>divide by 3600 to get 60 Wh, and divide by 1000 to get 0.06 kWh.

I don't want to convert my current watts into Kwh(I know that's possible and
how to). I want to see how many watts I have used the last hour... on that
exact timing.

Hmm.. for example if I have a graph for the last hour showing my minute-data
where I see a rate changing between 20 to 60 watts over this hour then I
want to go an hour backwards in time and summarize for an hour... and show
that in the same graph.

So this is maybe some kind of double-graph where I have my normal one hour
graph on the first Y-axis and another summarized one hour graph on the other
Y-axis.

Not sure I even can explain it, so how should it then be possible ;-)

But anyway... I am thinking of another way to do this. I will just put all
my data into my MySQL database and summarize it in there and then create a
new RRD graph out from the summarized values in there. It could be a long
way around but I just simply don't understand RRD that well.
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