Pulse to m³/h

[pklok]

one pulse is 0,01 m³ it is a gasmeter pulse how can i convert it to m³/h have some one a function blok for it. Patrick

[pfort]

First you have to decide a sampling period. As an example, lets say you decide 1 sec. period: For each pulse/sec you have 0,01m³/sec x 3600sec/hour = 36m³/hour

[pklok]

Thanks but i know the formula but my problem is how can i measuring the time between 2 pulses on a good way.

[Mendon Systems]

The answer depends a bit on the frequency of your input. If the input frequency isn't real low you can set the PRV instruction up to return the frequency. If the pulse rate is too low then you need to read the count over a fixed time period (perhaps once per second) and reset the HS counter then calculate the frequency from that result. If the pulse rate is really low then set up a scheduled task to read the pulse count periodically and use the AVG function to average the pulse count.

[digispark]

As above, frequency of the pulse do matter with the choice of calculation method. Do you know what is the operating range of this flow meter? what is minimum and maximum flow rate? Is it a constant flow or it activates infrequently?

[pklok]

The pulse is activates infrequently. i wanted to monitor my home gas pulse and i will see the m³/h if the heater is on.

[panic mode]

there are many ways to do this but since pulses are infrequent I would prefer to use totalizer and then compute the rate. for example you could just: a) count pulses (to get total in 0.01 m^3/h) b) have free running timer that is preset to one minute (60sec) c) have array of 60 samples (one reading every minute) d) every minute (that's our timer) increment index with rollover (0-59) and use it to save current total count to a location in sample array. also compute difference between the current total and oldest sample (1h or 60min old). that difference is your result in 0.01m^3/h. hint: oldest sample is just next value in your sample array (with rollover). of course you can do a variation of it (timer set to 2min and use 30 samples for example). if you choose period other than 60 min, you need to scale result

[Mendon Systems]

There are lots of variations of panic mode's approach you could use. For example, the pulse rate may be slow enough that you could count an entire day with a simple counter and do the calculation once per day. Another thing to consider also is the pulse duration. Is the pulse on long enough that you can use a normal PLC input or do you need a high speed counter input to pick it up?? The answer depends on what PLC you are using.

[pklok]

Thanks