# RS Logix Flow Rate

• posted

Using SLC5/03 & RS Logix.
I have a pump that pumps water at about 5 litres a minute. The flow is
measured from a DP cell across an orifice plate. The 4-20 mA signal from the
DP Cell is linearised by the square root function in the plc program.
How can I take the linearised flow signal and give me a readout of pump
flowrate and total flow within the plc. I only want the readings in the RS
logix program and not to an external device. The readings need to be in
engineering units litres per minute & total litres.
TIA
• posted
If the formula really linearizes the curve -- in practice, not just in theory -- then all you need to do to get the rate is multiply by an appropriate scale factor. Determine that factor experimentally.
Total flow is obtained by integrating flow rate over time. For suitably short intervals, the accumulated sum of the flow rates at the start of each interval gives the total flow or a number proportional to it. You can calculate the proportionality constant from the calibrated rate and the measurement interval.
Jerry
• posted
If I understand your question correctly----To get instaneous flow rate is there any reason why you can't run a calibration of flow vs Delta P on a bench (vs doing it analytically) and then make a table of Delta P vs Flow. Input Delta P into this look up table to get flow. MLD
• posted
The setup is on a test rig. Just want the readout of flowrate & total in the plc program.
• posted
Have used non linear flow sensors as well Delta P across an orifice many times and got a flowrate readout on both a digital counter display as well as on a transient data tape and print out. Never had the need to know the absolute total flow. MLD
• posted
Google on "orifice plate flow calculator"