When used for liquid level applications, differential pressure transmitters measure which quantity?

When used for liquid level applications, differential pressure transmitters measure which quantity?

• A. head pressure
• B. differential pressure
• C. static pressure
• D. ambient pressure

Answer: (A)

In liquid level measurements with a differential pressure transmitter, what you’re sensing is the pressure difference produced by the liquid column. The pressure at the bottom of the tank is higher than the pressure at the top by an amount equal to the hydrostatic head of the liquid, which is ρ g h (density times gravity times height). That differential pressure is the head pressure, and it changes directly with the liquid height. So the transmitted signal represents this head pressure, not a single-point static pressure or the ambient/environmental pressure. The differential pressure reading is the raw sensor value, but in level applications it’s interpreted as head pressure to indicate how tall the liquid column is.

In liquid level measurements with a differential pressure transmitter, what you’re sensing is the pressure difference produced by the liquid column. The pressure at the bottom of the tank is higher than the pressure at the top by an amount equal to the hydrostatic head of the liquid, which is ρ g h (density times gravity times height). That differential pressure is the head pressure, and it changes directly with the liquid height. So the transmitted signal represents this head pressure, not a single-point static pressure or the ambient/environmental pressure. The differential pressure reading is the raw sensor value, but in level applications it’s interpreted as head pressure to indicate how tall the liquid column is.