# GLOSSARY OF TERMS: Pressure Measurement

Feb. 14, 2007

ABSOLUTE PRESSURE: Gage pressure plus atmospheric pressure. AMBIENT PRESSURE: Pressure of the air surrounding a transducer. BURST: The maximum pressure applied to a transducer sensing element or case without

ABSOLUTE: Absolute pressure (PSIA) is the gauge pressure plus atmospheric pressure.

AMBIENT: Ambient pressure is the pressure of the air surrounding a transducer.

BURST: Burst pressure is the maximum pressure applied to a transducer sensing element or case without causing leakage.

COMPENSATION: An addition of specific materials or devices to counteract a known error.

DEAD VOLUME: The volume of the pressure port of a transducer at room temperature and ambient barometric pressure.

DIAPHRAGM: The sensing element consisting of a membrane, which is deformed by the pressure differential applied across it.

DYNAMIC: Dynamic pressure is the difference in pressure levels from static pressure to stagnation pressure caused by an increase in velocity. Dynamic pressure increases by the square of the velocity.

ENTHALPY: The sum of the internal energy of a body and the product of its volume multiplied by the pressure.

EXPANSION FACTOR: Correction factor for the change in density between two pressure measurement areas in a constricted flow.

GAUGE PRESSURE: Gauge pressure (PSIG) is absolute pressure minus local atmospheric pressure.

HEAD LOSS: The loss of pressure in a flow system measured using a length parameter (i.e., inches of water, inches of mercury).

PSID: Pounds per square inch differential. Pressure difference between two points.

PSIS: Pounds per square inch standard. Pressure referenced to a standard atmosphere.

STAGNATION: Stagnation pressure is the sum of the static and dynamic pressure.

STATIC: Static pressure of a fluid whether in motion or at rest. It can be sensed in a small hole drilled perpendicular to and flush with the flow boundaries so as not to disturb the fluid in any way.

The terms and definitions for this issue’s Word Search come from a glossary of terms compiled by Omega Engineering (www.omega.com), a manufacturer of flow, level, pressure, and temperature measurement and control solutions.