A differential pressure (DP) cell is used to measure which parameters?

• A. Level and flow
• B. Temperature and pressure
• C. Pressure and level
• D. Flow and temperature

Answer: (A)

A differential pressure sensor reads the difference between two pressures. That differential pressure can then be converted into different process quantities depending on how the taps are arranged.

For level measurement, taps are placed to sense the hydrostatic pressure difference produced by the liquid column. The pressure difference equals the liquid’s density times gravity times the height of the liquid, so ΔP directly relates to level when density is known. For flow measurement, the taps are placed across a restriction such as an orifice or venturi; the drop in pressure across that restriction is related to the flow velocity through established flow equations, allowing calculation of flow rate.

Temperature isn’t measured by a DP cell itself, though temperature can affect fluid density and thus the calibration needed for accurate level or flow readings. The key point is that the same differential pressure signal underpins both level and flow measurements, not temperature.