1. Gauge Pressure Measurement – Gauge pressure is measured with reference to the standard atmospheric pressure at sea level (approximately 1013.25 mbar). Gauge pressure is positive when it is more than atmospheric pressure, and negative when it is lesser than atmospheric pressure.
2. Description of Measuring Instruments – The most commonly used device to measure gauge pressure is a Bourdon tube pressure gauge. It is a mechanical device which consists of a tube formed into a C-shape and sealed at one end. The sealed end is free to move a pointer over a scale according to the applied pressure within the tube, entering through the open end. Other mechanical devices like diaphragms and bellows can also measure gauge pressure. Among hydrostatic ones, the u-tube manometer is effective.
3. Applications – Gauge pressure measuring devices are the most widely used pressure measuring instruments for industrial purposes, particularly in power, refineries, chemical, petrochemical, pharmaceutical, food, refrigeration, air-conditioning and sanitation industries.