![]() On the other hand, temperature and pressure fluctuations have little effect on thermal mass flow meters. Additional mass flow sensors for these parameters, as well as a flow computer to correct for fluctuations in these process conditions, would be required for mass flow measurement. Variable area meters and turbine flow meters are volumetric measurement devices that are prone to temperature or pressure variations. Please note: Real caution should be taken in the measurement units each sensor is calibrated because, if the difference is not considered, it may result to an error of 7% – considering the high levels of precision and low total error band required in flow sensors for medical applications, for example, one can understand how important this is!įurther reading: How to calculate gas flow rate from a pressure measurement?ĭifferences between volumetric and mass flow meters ![]() Therefore, in order to maintain this principle, you can express mass flow in volume terms as long as the conditions for converting mass to volume are agreed upon (in other words if you agree on the “ reference conditions”).Īccording to the ‘European’ standard, a temperature of 0☌ and a pressure of 1,013 bar is defined as “ normal” reference conditions, indicated by the underlying letter “ n” in the unit of volume used (ln/min, m3n/h, etc).Ī temperature of 20☌ and a pressure of 1,013 bar are used as “ standard” reference conditions, indicated by the underlying letter “ s” in the unit of volume used (ls/min, m3s/h).įor the ‘American’ standard, the prefix “s” in sccm, slm or scfh refers to “standard” conditions 101.325 kPa absolute (14.6959 psia) and temperature of 0☌ (32☏). The majority of users, on the other hand, think and operate in volume terms. Mass & volumetric flow standardsįollowing the example above, you would consider that mass flow should be stated in weight units like g/h, mg/s, and so on. When we move the piston halfway to the bottom of the cylinder, the volume of air contained is only 1/2 liters, the pressure is increased to around 2 bar, but the mass remains the same, 1.293g, as nothing has been added or removed from the cylinder. This volume of air weights 1.293g, which equals the mass of the air enclosed to the cylinder. Secondly, assume that this cylinder holds 1.0 litre of air at ambient pressure (1 atm) and 0 oC temperature. ![]() Wondering what is mass flow and what is volumetric flow? Let’s see it this way:Īssume you have a 1.0 litre cylinder with a movable piston of negligible weight that closes it. This unit looks like a volumetric flow unit, but in truth expresses mass flow. Lien V, Vollmer F (2007) Microfluidic flow rate detection based on integrated optical fiber cantilever.ES Systems’ thermal gas mass flow meters measure flow in ln/min. Katayama K, Uchimura H, Sakakibara H, Kikutani Y, Kitamori T (2007) In situ microfluidic flow rate measurement based on near-field heterodyne grating method. Lee GB, Kuo TY, Wu WY (2002) A novel micromachined flow sensor using periodic flapping motion of a planar jet impinging on a V-shaped plate. Lab Chip 5(12):1344–1347Ĭzaplewski DA, Ilic BR, Zalalutdinov M, Olbricht WL, Zehnder AT, Craighead HG, Michalske TA (2004) A micromechanical flow sensor for microfluidic applications. Wu J, Ye J (2005) Micro flow sensor based on two closely spaced amperometric sensors. Lab Chip 4(1):7–10Īmatore C, Belotti M, Chen Y, Roy E, Sella C, Thouin L (2004) Using electrochemical coupling between parallel microbands for in situ monitoring of flow rates in microfluidic channels. Meas Sci Technol 14(8):1321–1327Ĭollins J, Lee AP (2004) Microfluidic flow transducer based on the measurement of electrical admittance. Analyst 128(6):543–546Īyliffe HE, Rabbitt RD (2003) An electric impedance based microelectromechanical system flow sensor for ionic solutions. Nakagama T, Maeda T, Uchiyama K, Hobo T (2003) Monitoring nano-flow rate of water by atomic emission detection using helium radio-frequency plasma. Markov DA, Dotson S, Wood S, Bornhop DJ (2004) Noninvasive fluid flow measurements in microfluidic channels with backscatter interferometry. Wu JA, Sansen W (2002) Electrochemical time of flight flow sensor. Scholer L, Lange B, Seibel K, Schafer H, Walder M, Friedrich N, Ehrhardt D, Schonfeld F, Zech G, Bohm M (2005) Monolithically integrated micro flow sensor for lab-on-chip applications. ![]()
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