How does a DP cell measure flow?

• A. The plate divides the flow
• B. By counting bubbles
• C. By measuring hydrostatic pressure
• D. By detecting temperature change

Answer: (A)

A differential-pressure flow measurement relies on a restrictive element that divides the flow and creates a pressure difference between upstream and downstream taps. As fluid passes through the restriction (like an orifice plate), the flow is constricted, causing the velocity to rise and the static pressure to drop across the plate. The DP cell sits across those two points and converts that pressure difference into a signal. Because the pressure drop relates to the flow rate for a given fluid density and geometry, the transmitter’s output represents how much flow is occurring. Other ideas, like counting bubbles or measuring a single hydrostatic pressure or a temperature change, don’t capture how a DP device derives flow from the difference in pressure created by the flow restriction.