Which type of pressure sensor uses a second process pressure as a reference instead of atmospheric pressure?

• A. Differential pressure
• B. Gauge pressure
• C. Absolute pressure
• D. Sealed pressure

Answer: (A)

Differential pressure sensors use two process pressures as their reference points, not the surrounding atmosphere. They have two sensing ports, so the output reflects the difference between the two pressures on those ports. This makes them ideal for measuring things like flow across a restriction, filter pressure drops, or level in a tank where you want to know how much pressure change exists between two process points.

In contrast, gauge sensors reference atmospheric pressure, so they measure pressure relative to ambient. Absolute sensors reference a vacuum (zero pressure), not the atmosphere, while sealed sensors keep a fixed internal reference that’s not another process pressure.