Thermo Scientific HB-S200, User Manual

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Sarasota 200 Ultrasonic Multipath
Flowmeter
Section 6 CALIBRATION/VERIFICATION Page 6-1 Thermo Fisher Scientific
CALIBRATION/
VERIFICATION
6 CALIBRATION/VERIFICATION
Flowmeters of this type do not normally require calibration. Exceptions are where there are
significant unmeasured areas, for example, behind transducers, or where local conditions
might create atypical velocity profiles and a small number of velocity paths are deployed. See
Section 1: Introduction and Appendix 3: References.
However, it is normal to carry out periodic checks to verify the overall performance of the flow
determination.
Whether for calibration or verification purposes, the comparison method to be used will be the
same and will depend on the site.
Reference is made to ISO 748 for details of methods. See Appendix 3: References.
The most common method used is by current metering using a calibrated rotating element or
electromagnetic current meter. Recently the use of an acoustic Doppler profiler (ADP) has
become more common for this purpose. This has enabled the checking process to become
much quicker and, where high flows in rivers are concerned, safer too.
Care should be taken to use repeated checks and to minimise the experimental uncertainties
which could otherwise be greater than the uncertainty of the ultrasonic flowmeter.