Alain Thanks for the reply. I would like to use the pic16f877 (since I have a few onhand) but I was concerned it would behave similar to the 16f84a that I am currently using.

I was experiencing a large variation in the incremented variable despite the fact that the time between the sensors was very precise. (I use the raw counts in a flow calculation.) The actual time between the sensors varies from 2 - 5 seconds depending on the flow. The raw counts for the variable (value) are approximately 33,000 for 1 ml/min flow. The variablity was more than 25% between successive measurements and I also observe a decay in the counts.

I thought a chip with more capacity would help. I realize now that it is a large leap from one to the other since I will have to rewire the processor board to the 18f pinout.

If there is a chip you could recommend that would meet the data and calculation needs while trimming down the unused peripherals that would be appreciated as well.

Thanks