Măsurări mecanice - presiunea

Pressure

Pressure Measurment

Many techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure pressure are called pressure gauges or vacuum gauges.

A manometer is a pressure measuring instrument, usually limited to measuring pressures lower than atmospheric. It is often used to refer specifically to liquid column hydrostatic instruments.

A vacuum gauge is used to measure the pressure in a vacuum, which is broadly divided into two categories: high and low vacuum (and sometimes ultra-high vacuum). Many of the different techniques used to measure these categories have an overlap at some point in the pressure range. By combining several different types of gauge it is possible measure system pressure from 10 mbar down to 10e-11 mbar.

Applications

Manometer

Barometer

McLeod Gauge

Depth gauge

Boost gauge

Tire-pressure gauge

Sphygmomanometer

Instruments

Many instruments have been invented to measure pressure, with different advantages and disadvantages. Pressure range, sensistivity, dynamic response and cost all vary by several orders of magnitude from one instrument design to the next. The oldest type is the liquid column manometer invented by Evangelista Torricelli.

Manometers

A Manometer is a device to measure pressures. A common simple manometer consists of a U shaped tube of

glass filled with some liquid. Typically the liquid is mercury because of its high density.

Manometers

Manometers

Barometers

Water-based barometers

This concept of "decreasing atmospheric pressure predicts stormy weather" is the basis for a primitiveweather prediction device called a weather glass or thunder glass. It can also be called a "storm glass“or a "Goethe thermometer" (the writer Goethe popularized it in Germany).It consists of a glass container with a sealed body, half filled with water. A narrow spout connects to the bodybelow the water level and rises above the water level, where it is open to the atmosphere. When the air pressure is lower than it was at the time the body was sealed, the water level in the spout will rise above the water level in the body; when the air pressure is higher than it was at the time the body was sealed, the water level in the spout will drop below the water level in the body.