A hypothetical, ideal body which absorbs completely all incident radiation. independent of wavelength and direction. No actual substance behaves as a true black body, although platinum black and other soots rather closely approximate this ideal. However, ...

A decrease in the central pressure of a pressure system. Usually applied to a low rather than to a high.

In nautical terminology, a contraction for "weather glass" (a mercury barometer).

That horizontal wind velocity at which the Coriolis acceleration exactly balances the horizontal pressure force. It is directed along contour lines or isobars.

The transducer's output when the maximum sensed value is applied to the transducer's input. For example, the F.S. output of a 4-20 mA transmitter is 20 mA, whereas its span is only 16mA.

An instrument for measuring the pressure of gases and vapors. A mercury barometer is a type of manometer.