A differential-pressure flow signal may already contain square-root extraction. Identify that processing before scaling it again in a controller.
Identify the Physical Basis
For a fixed primary-element and fluid basis, flow varies with the square root of differential pressure. Endress+Hauser’s DP-flow explanation describes this relationship and the other physical terms involved. The measured pressure signal and a calculated linear flow signal therefore are different quantities, even if both are transmitted over an identical electrical interface.
Work Through an Example
In a hypothetical fixed-basis case, a DP of 25% of the reference maximum corresponds to 50% of the reference flow: √0.25 = 0.50. If a transmitter has already produced that 50% flow output and a controller takes its square root again, it calculates about 70.7%. If neither stage extracts the square root, it may report 25%. Both mistakes come from processing identity rather than a change in the liquid.
Use the Result in the Review
Trace the quantity at each stage: primary pressure difference, transmitter output, controller scaling and displayed rate. Record where square-root extraction is enabled and which stage owns it. Preserve range and fluid-density assumptions with that map. Compare the configurations against one shared physical test point before assuming a discrepancy is a defective sensor. The complete DP equation still needs its selected primary-element factors.
A flowmeter filling discussion must confirm its actual instrument principle before this question applies. This guide explains a DP-processing boundary; it does not assert an installed DP device, recommend an orifice geometry or treat the simplified normalized illustration as a full flow calculation.
Has square-root flow extraction been accounted for at the correct system boundary?
This blank worksheet is for your own project. It contains no H M machine trial result.
| Review field | Reference or result | Responsible person |
|---|---|---|
| Selected primary element and fluid basis | To complete | To complete |
| Quantity and range at transmitter output | To complete | To complete |
| Single square-root extraction owner | To complete | To complete |
| Controller scale and shared test point | To complete | To complete |
Customer Questions
Should every flow signal be square-rooted?
No. Apply it only where the selected signal represents DP and needs that conversion.
Is a 50% electrical output always 50% DP?
No. The configured output may already be linear flow.
Does square-root extraction establish the whole DP calculation?
No. Density and primary-element factors remain part of the basis.
Related Equipment References
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Primary References
These references support the technical principles discussed in this guide. The worked examples and review questions are educational.
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