Since the middle of the 17th century, when Italian physicist Evangelista Torricelli discovered that a glass tube filled with mercury could be used to measure atmospheric pressure, liquid-column manometers have been used as a primary standard to measure pressure. Even today, they operate on the same principle that pressure can be determined if you know the density and the differential height of a liquid-column manometer, as well as the acceleration due to gravity. The problem with making reliable pressure measurements in modern research and industrial processes, which can range from ultra-high vacuum (10 8 Pa) to atmospheric pressure (105 Pa), is that many kinds of gauges are required from ionization and spinning-rotor gauges to capacitance-diaphragm and resonant-silicon gauges. However, the improper use or incorrect calibration of any of these can result in unreliable measurements that cost time and money. It is therefore vital that gauges should be traceable to the SI system of units, which have been accurately measured by standards laboratories, such as the National Institute of Standards and Technology (NIST) in the US and other national metrology institutes around the world. Indeed, developing and maintaining suitable high-accuracy standards that allow traceability to the SI units is one of the most significant challenges in vacuum metrology. Standards labs are thus responsible for developing these standards for the unit of pressure the pascal (Pa).
Citation: Physics World
Pub Type: Journals
Atmospheric Pressure, Barometer, Capacitance Diaphragm Gauge, Ionization Gauge, Pressure Calibration, Pressure Metrology, Pressure Standards, Quartz Bourdon Gauge, Resonance Silicon Gauge, Spinning Rotor Gauge, Transfer Standards, UHV, UIM, Ultra High Vacuum, Ultrasonic Interferometer Manometer, Vacuum Calibration, Vacuum Metrology