How to Display Flow Rate from a DP Transmitter

DP Flow via Square Root Extraction | An Acromag Solutions Video Application Note

A water treatment facility has differential pressure (DP) transmitters that they want to display the flow rate from. The output is a 4 to 20mA signal to their SCADA system. They also want to display the flow rate to the operators working nearby; but the signal from the differential pressure transmitter is nonlinear.

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Click on the AcroMaggie video below to learn how to Display Flow Rate from a DP Transmitter.

System Requirements to Display the Flow Rate from a DP Transmitter:

The panel meter must be able to perform a square root calculation on the incoming signal; to display the flow in gallons per minute. The display also must have large, easily read characters. The signal to the SCADA system cannot be interrupted, even if the display is down for any reason.

Implementing the Solution:

  1. Use Acromag’s SP336 to split the 4-20mA signal; which will fully isolate the loop to the SCADA system from the loop to the display.
  2. Acromag’s VPM3000 panel meter can extract the square root from a 4-20mA signal and display the gallons per minute in bright red 1.2” characters. The user-selectable low-flow cutoff feature gives a reading of zero when the flow rate drops below the user-selected value. Options for user-settable relay alarm outputs for low and high flow rate are available.
  3. The SP336-0700 defaults to 4-20mA in and two 4-20mA signals out. But it can be scaled differently with either the Acromag Windows® based software or the Agility™ app.
  4. The VPM3000 can easily be configured from the front panel pushbuttons or with Acromag DisplayWizard software.

VPM3000 Series Panel Meter: Universal Transmitter / Alarm with Display

SP336-0700: Four-Wire Current / milliVolt Signal Splitter

Why Acromag for this I/O Solution:

The square root calculation feature saves money because no additional computation units are necessary. Combining a signal splitter with a panel meter creates a convenient and fail-safe display of the flow rate. Both units are easily configured with Acromag’s free software. Furthermore, Acromag guarantees technical support within one business day!