Thanks, I'm doing that now. I've got values for the flowmeter input, its readings and a 'standard' curve for the new impulse flow sensor. I shall do a physical check on that measuring the liquid volume, number of counts and use a stop watch. Where I'm blind is achieving a modified output pulse stream related to changing frequencies at the input? It's most important that the number of pulses output from the flow sensor over time puts the correct count into the meter, because these values are used to display accumulate total volume of liquid. If my new flow sensor produces more pulses I could count them, drop n in x pulses and send the result to an io port. Although it would be nice to get a continuous output pulse stream, it doesn't matter if there are timing gaps, as long as the total number of pulses counted by the flowmeter and therefore accumulated volume is correct.