ISO INTERNATIONAL STANDARD 2537 Fourth edition 2007-05-01 Hydrometry Rotating-element current- meters HydrometrieMoulinetsaélementrotatif Reference number A ISO 2537:2007(E) ISO @ISO 2007 ISO2537:2007(E) Contents Page 1 Scope 2 Normativereferences 3 Termsanddefinitions 4 Principle ofoperation 5 Types of current-meters 2 6 Operational requirements...... 2 7 Characteristics of cup-type and propeller-type current-meter 3 8 Constructionfeatures 3 9 Calibration (rating). 3 10 Maintenanceofcurrent-meter 6 Operationalandservicingmanual 6 Annex A(normative)Construction features of current-meters AnnexB(normative)Maintenanceofcurrent-meter 11 Bibliography 13 ili ISO 2537:2007(E) Foreword IsO (theInternational OrganizationforStandardization)isa worldwidefederationof nationalstandardsbodies (isO member bodies). The work of preparing International Standards is normally carried out through IsO technical committees. Each member body interested in a subject for which a technical committee has been ElectrotechnicalCommission(lEC)onallmattersofelectrotechnicalstandardization adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 %of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent ISO 2537 was prepared by Technical Committee ISO/TC 113, Hydrometry, Subcommittee SC 5, Instruments, equipmentanddatamanagement. This fourth edition cancels and replaces the third edition (IsO 2537:1988), which has been technically revised. Is02007-Allrights reserved ISO 2537:2007(E) INTERNATIONALSTANDARD Hydrometry Rotating-element current-meters 1 Scope This International Standard specifies the operational requirements, construction, calibration, and maintenance ofrotating-elementdevicesforthemeasurementofflowvelocitiesinopenchannels IsO748gives informationon theuseofthesedevices. 2Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IsO772,Hydrometricdeterminations-Vocabularyandsymbols Iso3454,Hydrometry-Direct depthsounding and suspension equipment ISO3455,Hydrometry-Calibrationofcurrent-metersinstraightopentanks 3 Terms and definitions For the purposes of this document, the terms and definitions given in IsO 772 and the following apply 3.1 propeller pitch distance the propeller current-meter relatively moves through the water during one revolution 4 Principleof operation 4.1 Proportionality The rotating element of a current-meter is driven by the fluid at an angular velocity that is proportional to the local velocity of the fluid at the point of immersion when that velocity exceeds a critical value. 4.2Flowvelocity In order to determine the velocity of the fluid, a current-meter is placed at a point in a stream and the number of number of revolutions is observed.The velocity is obtained from the current-meter calibration table or calibration equation(s), established experimentally during its calibration (Clause 9). The number of current-meter revolutions (rotations) may be determined by sensing the signals emitted (such as electrical pulses)through the thespeedofrotationoftherotatingelementbymeansofequipmentdesignedforthispurpose. 1 ISO2537:2007(E) 5 Types of current-meters 5.1 General cup-type and horizontal axis propeller-type. 5.2 Cup-type current-meter intervals around the perimeter of a hub, which rotates whenplaced in a fluid flow.Usually,the rotoris mounted with the axis vertical. 5.3Propeller-type current-meter equal intervals around the perimeter of a hub, or two or more helical screw blades formed around a hub that rotatesaboutahorizontalaxiswhenplaced inafluidflow. 6Operational requirements 6.1 Positioning The current-meter shall maintain a