We've installed four Mass Flowmeters with a pulse output signal and bringing the signal in to an M-Series Multifunction I/O card and PIN function block. The 24 VDC power for the pulse signal is provided from the carrier through the 32pin terminal block as shown in BOL for the multifunction I/O card. We've set the parameters (pulse width, pulse rate, pulse_val, time_units) and the frequency shown in DeltaV Diagnostics is ~2000 Hz. We are seeing somewhat erratic flow signals which we resolved by adjusting the Pulse rate (cc/P) at the flow meter and Pulse_val on the PIN block to achieve a higher frequency. We also have flowmeter where the flowrate at the DCS is ~30% higher than displayed in the field at the flowmeter (converter). Similar applications onsite have capacitors installed at the input terminal blocks in the DCS cabinet, or ferrite modules on the input cable at the I/O Card. We think we need to do the same, but I'm having a hard time finding any documentation on this in guardian or Books online (which just says a filter may be needed). Can anyone help me understand which should be used and why?
Kathy Pate
Toray Carbon Fibers America
Decatur, AL 35601
kathy.pate@toraycma.com