Rate of increase of an analog signal

Hi,

I'm having some trouble.

 I have a 1000 liter tank of water that is measured with a 4-20mA level transmitter.  Water is flowing into the tank and I want to display how fast the tank is filling in liters per minute.

I have a very messy way of doing it.  Use counters to store the analog value, wait 5 seconds, compare it to the live value, multiply by 12 for minutes.  Then reset the counters to the new value and restart the process.

Perhaps if there is a way to create a pulse for every liter added, I could use  the same logic as calculating RPM.

Certainly there is a better way but I can't figure it out.  Any help greatly appreciated.

Thanks

It takes about an hour to fill.  Flow rates to the tank should be between 5 and 30 liters per minute.

Thanks

Hi,

LOGO will convert that 4-20mA signal into 0-1000 , and according to your situation it means 1 value is 1 litre. 

Measure the time taken to increase by 1 value and divide 60 by this, this way is better as you will get the actual result.