Flowmeter NPN Output

Hi,

Could I ask for some help, I'm getting bogged down in a simple DAQ VI. I am using a flowmeter outputting a series of NPN pulses through the counter line on my USB-6501. I have set the DAQ Assistant within a For Loop that counts the pulses within each iteration but naturally after each iteration the count resets to zero so

my indicator (gauge in this case) appears erratic despite a steady flow through the meter. How would I go about creating a VI that can output a steady reading on

the indicator but still be senstive to changes in flow? Thank you very much for any help.