I am currently using LabVIEW 2009 to measure and record frequencies generated by 8 small turbine flowmeters. The flowmeters generate pulses at 24V which need to be counted in all 8 pins of my NI9421 module. I have read all the product manuals, spoken with NI tech support, and tried all kinds of variations in code to measure an appropriate value.
Currently, we can read a frequency (30Hz to 350 Hz confirmed) using the DAQ assistant alone and using the 2 Counter Large Range measurement method. This only works for frequencies above 0 Hz. If we use any other method (single or dual counters), the values are completely wrong and inconsistent. When the flow stops, the VI times out (this is true of all cases) and throws out erroneous numbers. I need to figure out how to accurately read a frequency on each of these flowmeters with my DAQ setup and then how to route the terminals so that all pins can be read. Based on pin drawings and route diagrams, I believe I need to route the following:
/cDAQ2Mod4/PFI0 -> /cDAQ2/Ctr0Source
/cDAQ2Mod4/PFI1 -> /cDAQ2/Ctr0Gate
/cDAQ2Mod4/PFI2 -> /cDAQ2/Ctr2Gate
/cDAQ2Mod4/PFI3 -> /cDAQ2/Ctr2Source
/cDAQ2Mod4/PFI4 -> /cDAQ2/Ctr1Source
/cDAQ2Mod4/PFI5 -> /cDAQ2/Ctr1Gate
/cDAQ2Mod4/PFI6 -> /cDAQ2/Ctr3Gate
/cDAQ2Mod4/PFI7 -> /cDAQ2/Ctr3Source
I have tried using property nodes with frequency terminal properties, DAQmx tasks, etc. with no luck. Any help in the next day or so would be greatly appreciated. Thanks.