A little help with SCL and array's if you dont mind

HI all

i have a calculation in Tia portal V15.1 that calculates a gas flow rate but now i need to convert that flow rate into an average so i can work out the cost of the gas.

I need to take samples of the flow rate every 10s (this is variable) for all the time the heater is running then at the end do some simple maths to calculate the average ( mean / sum of samples)

The thing is, i don't know how many samples it would be because that depends on the heater being on, so i think this rules out an array (i think)

SCL is not my strong point so if anyone who can assist, it would be mostly appreciated.

as mentioned by jacek, it would be logical directly calculating the volume of gas, instead of doing a rolling average. There are a couple of reasons for this, but mainly you need to know how long (how many samples) the average will be calculated. At a sampling of 10s you need 60 samples for 10 minutes, for 10 hours you will need 3600, and this as far as array indexes go is starting to get into the ridicolous.

to get volume you can simply add the flow rate at a fixed interval.

the first step is to get your flow rate at a adequate time constant, since you were mentioning a sampling of 10s, let's get your flow to example l/s. then every second you add the flow to the volume.

//lets read the local time
return := read_loc_t(localTime);
//when the seconds change
if localTime.SECONDS <> oldLocalTimeSeconds then
    //increment the volume by the flow
    volume += flow;
    //count how many s the process runs
    if flow <> 0 then
        processTimeElapsed += 1;                  
    end_if;
end_if;
//store the time for next cycle
oldLocalTimeSeconds := localTime.SECONDS;         

For billing purposes you really only need the volume, however if you want you can calculate your average flow by doing volume/processTimeElapsed.

hope this helps