Hi,

My water meter delivers one pulse per liter consumed. I have a script that 
counts the pulses (raspberry and piface).

Periodically I want to store in the RRD database  the number of pulses.
The first solution is to periodically store the number of impusions since the 
last backup.
The second solution is to periodically store the total impusions since the 
start of counting

Which to choose? The second solution requiring an intermediate backup in case 
of bugs(!) or system reboot

For graphs, displaying data on last 5 minutes, last hour, last day, last month 
should be enough.

Thank you for your reply.

Bruno

----- Mail original -----
De: "Simon Hobson" <li...@thehobsons.co.uk>
À: rrd-users@lists.oetiker.ch
Envoyé: Lundi 29 Septembre 2014 11:48:28
Objet: Re: [rrd-users] Bar graph by hour, day, month

Bruno Suarez <bsua...@free.fr> wrote:

Some clarification is needed, it could be that you are using terms that mean 
one thing to you and something else to us.

> I want to make graphs of water consumption.
> I have a counter that is incremented for every liter of water consumed,
> this counter will be stored in the database and reset every minute.

Can you clarify that.
I take you mean you'll be reading the counter and updating the RRD file every 
minute, but does the act of reading the counter reset it to zero or not ?

> In the end I would make graphs (bar) to view the water consumption for
> each period (eg 5 min, 1 hour, 1 day, 1 month ...)

Do you want the bars to match specific time periods - eg have a bar that covers 
1st Sept to 30th Sept and so on ?
5 minutes is fairly easy - if your RRD consolidates data to a minimum 
resolution of 5 minutes then that's what you'll get. But once you get up to 
days and weeks it gets harder - depending on what you want.
Showing a graph of "the last 7 days" or "the last 31 days" is easy. Doing it 
for "the last calendar week" (Sun -Sat or Mon-Sun) or "last calendar month" 
(1st to 28th/30th/31st) is somewhat harder.

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