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HART monitoring of Flowmeters to increase Accuracy

Many industries rely on the availability of water for their processes and to succeed in the current climate, companies must adapt to the changing conditions. Major companies are now marketing their “green” credentials.  With iron ore mining, saving water in the washing process can lead to further savings down the process chain where water usage could be as high as 800 cubic meters/hour for the processing of 800 tons/hour of ore.  The primary water source is saline water from underground bores, they manage the water resource with water re-injection, and the process owner is accountable for the water use. To achieve this the engineers require an improvement in accuracy over the existing 4-20mA loop from the magnetic flowmeters to their PLC,  where they have also identified the totalization of the pulse count from the meter is not accurate.

With the existing magnetic flowmeter, they can tap into the improved digital resolution of the meter using HART protocol and the HCS HART to MODBUS Converter. The HCS is connected in parallel with the existing 4-20mA loop, and reads the primary process variable (PV) → Volume flow plus secondary process variable (SV) → Totalizer.

HART monitoring of Flowmeters to increase AccuracyDownload the PDF file

Additional Considerations
In some applications, flow rate and flow totalization are critical variables. A facility will use a flowmeter that they believe is producing accurate flow measurement and integration, but by the time that data gets into the SCADA, the values are questionable. There are several variables that may contribute to the questionable data quality like the accuracy and resolution of your input cards or timing issues in reading a pulse output.

Reading the data digitally can eliminate any and all variables. Since the flow rate and totalization are already digital in the flowmeter, a HART master product like the HCS can be used because it takes the 32-bit floats from the flowmeter and delivers them as MODBUS 32-bit floats to the SCADA. Once the rate and totalization is digital, it is best to keep it digital all the way back to the destination, and the HCS accomplishes that with its serial MODBUS RTU, RS-485 output. If Ethernet communications is required instead, the HES HART to Ethernet Gateway System outputs over Ethernet using the MODBUS/TCP protocol.

Key attributes:

  • Keeping the signal digital increases accuracy and saves money
  • HART to MODBUS conversion
  • Get more data to your SCADA system

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