Pressure & Vacuum What is pressure? What is vacuum? Table of Contents Pressure is defined as the force applied over Vacuum is defined as an enclosed space an area, such as the wall of a container or in which the pressure has been reduced as part of a manufacturing process. The below surrounding atmospheric pressure. Mechanical Gauges common English unit for pressure is pounds Gauges, meters, and controllers measure Commercial and per square inch, or psi. To convert from psi to the absolute pressure in a vacuum system. Industrial 568–569 other units, see the conversion table below. How is it measured? Sanitary 569 How is it measured? Bar: a unit of vacuum or pressure. The Psig (Gauge Pressure): a measure of unit mbar (millibar) is used to define small pressure in psi that is referenced to ambient changes in pressure. pressure. Inches of Mercury (" of Hg): the English Digital Gauges Psia (Absolute Pressure): a measure of unit for measuring vacuum. The Vacuum 568–570 pressure in psi that is referenced to zero international standard unit for vacuum absolute pressure. is millimeters of mercury (mm of Hg). Industrial 572–573 High-Accuracy 570–571 Psid (Pressure Differential): a measure of Pascal (Pa): the unit for measuring the difference between two pressures. vacuum or pressure in the International Test 573 System or SI. One pascal equals one Manometers 577–579 BFSL (Best Fit Straight Line) Accuracy: newton (SI unit of force) per square meter. a transmitter’s percent deviation from the best 105 Pa equals 1 bar. fit straight line to the transmitter pressure vs output curve. See figure below. Torr: the provisional international standard unit to replace inches of Hg. One torr is 1/760 Monitors/Controllers/Systems BFSL accuracy of a standard atmosphere (the air pressure Pressure Monitor 574 Typical measured at mean sea level). transmitter response Vacuum and Pressure 578 How are units converted? Full-scale or To go from Multiply by To get Current (mA) terminal point " of Hg 3.3864 kPa Switches accuracy " of Hg 33.864 mbar " of Hg 25.400 torr Gauge and Differential Pressure (psi) kPa 0.2953 " of Hg Pressure ColeParmer.com kPa 10.000 mbar Compound Gauge: a gauge that indicates kPa 7.5008 torr both pressures above and below ambient mbar 0.02953 " of Hg mbar 0.100 kPa pressure. mbar 0.75008 torr Transducers Liquid-Filled Case: a case filled with either torr 0.039370 " of Hg Sanitary 574 glycerine or silicone to at least 75% of its total torr 0.13332 kPa torr 1.3332 mbar Industrial 575 internal volume. Protects the internal parts from damage due to vibration, pulsation, or ambient High-Accuracy 575–576 corrosives. Differential Pressure 576 Absolute, gauge, and Process Connection: the size and type of the connection to your system. differential pressure scales How are units converted? Regulators To go from Multiply by To get Laboratory and bar 14.50 psi Industrial Gas bar 401.47 " of H2O Regulators 579–580 bar 29.53 " of Hg Manual Pressure bar 100.0 kPa bar 1000 mbar Regulators 581 bar 1019.73 cm of H2O bar 750.06 mm of Hg " of H2O 0.036127 psi " of H2O 0.073554 " of Hg I/P Transducers " of H2O 0.2491 kPa " of H2O 2.491 mbar Industrial and " of H2O 2.5400 cm of H2O Explosion-Proof 581 " of H2O 1.8683 mm of Hg psi 27.680 " of H2O psi 2.036 " of Hg psi 6.8947 kPa psi 68.947 mbar Use differential pressure sensors to measure Find Even psi 70.308 cm of H2O gauge pressure by leaving one process connec- psi 51.715 mm of Hg tion open to atmosphere and connecting the More Online! kg/cm2 14.223 psi second sensor port to your system. 2 kg/cm 393.7 " of H2O Go to kg/cm2 28.96 " of Hg kg/cm2 98.06 kPa ColeParmer.com for kg/cm2 980.6 mbar 2 our full selection. kg/cm 1000 cm of H2O kg/cm2 735.5 mm of Hg Toll-free: 800-323-4340 Fax: 847-247-2929 [email protected] www.coleparmer.com Cole-Parmer® 567.