ISO 14511 pdf download.Measurement of fluid flow in closed conduits — Thermal mass flowmeters
1 Scope
This International Standard gives guidelines for the specification, testing, inspection, installation, operation and calibration of thermal mass gas flowmeters for the metering of gases and gas mixtures. It is not applicable to measuring liquid mass flowrates using thermal mass flowmeters. This International Standard is not applicable to hot wire and other hot film anemometers, also used in making point velocity measurements.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 4006, Measurementoffluidflowin closedconduits — Vocabularyandsymbols ISO 7066-2, Assessment of uncertainty in the calibration and use of flow measurement devices — Part2: Non- linearcalibration relationships Guide to the expression ofuncertaintyin measurement (GUM). BIPM, IEC, IFCC, ISO, IUPAC, IUPAP, OIML, 1 st edition, corrected and reprinted in 1 995 IEC 61 000-4, Electromagnetic compatibility(EMC) — Part4: Testing andmeasurement techniques
3 Terms and definitions
For the purposes of this International Standard, the terms and definitions given in ISO 4006 and the following apply. NOTE The term “gas” is used as a synonym for single gases, gas mixtures and vapours. 3.1 General terms 3.1.1 flowrate quotient of the quantity of fluid passing through the cross-section of a conduit and the time taken for this quantity to pass through this section NOTE In this International Standard.3.1.2 mass flowrate flowrate in which the quantity of fluid is expressed as a mass NOTE The term “flowrate” is used as a synonym for mass flowrate in this International Standard, unless otherwise stated. 3.1.3 accuracy of measurement closeness of the agreement between the result of a measurement and a true value of the measurand NOTE Accuracy is a qualitative concept. 3.1.4 uncertainty of measurement parameter, associated with the result of a measurement, that characterizes the dispersion of the values that can reasonably be attributed to the measurand 3.1.5 repeatability measuring instrument ? ability of a measuring instrument to provide closely similar indications for repeated applications of the same measurand under the same conditions of measurement
3.1.6 flow profile graphic representation of the velocity distribution NOTE The point flow velocity across the cross-section of a conduit is not constant. It varies as a consequence of upstream and downstream disturbances and with the Reynolds number of the flow stream. For a fully developed flow, the point flow velocity varies from 0 m/s at the pipe wall to a maximum value at the conduit centre. The flow profile describes the variation of the flow velocity across the conduit cross-section and may be expressed mathematically or graphically. 3.2 Specific terms 3.2.1 sensor element of a measuring instrument or measuring chain that is directly affected by the measurand 3.2.2 laminar flow element element inserted into the gas stream to establish a constant ratio between the main flow stream and the bypass flow through the sensor3.2.3 thermal mass flowmeter TMF meter flow-measuring device which uses heat transfer to measure and indicate mass flowrate NOTE The term thermal mass flowmeter also applies to the measuring portion of a thermal mass flow controller and not the control function. 3.2.4 capillary thermal mass flowmeter CTMF meter TMF meter normally consisting of a laminar flow element, bypass tube (capillary), temperature sensors (some designs include a separate heater) with supporting electronics and housing 3.2.5 insertion and/or in-line thermal mass flowmeter ITMF meter TMF meter normally consisting of one or two temperature sensing sensors (some designs have a separate heater) with supporting structure, electronics and housing, of which the sensors are exposed to the full gas stream