ISO 6416:2017

Overview

ISO 6416:2017 - "Hydrometry - Measurement of discharge by the ultrasonic transit time (time of flight) method" describes how to establish and operate an ultrasonic transit-time gauging station for continuous measurement of discharge in rivers, open channels and closed conduits. The standard covers the physical principles, instrumentation performance, commissioning, verification, operation and procedures specific to the ultrasonic transit time (time-of-flight) technique. It is limited to transit-time systems (not Doppler, correlation or level-to-flow methods) and excludes measurement in rivers with ice. Note: IEC 60041 covers full-pipe applications.

Key topics and technical requirements

• Principle and physics: transit-time/time-of-flight measurement fundamentals and sound propagation in water (speed of sound, propagation losses, path bending, reflections).
• Flow velocity determination: calculation of discharge from transit-time measurements, single- and multi-path configurations, crossed and reflected paths.
• Gauge configuration: single-path, multi-path, reflected-path, transponder and wireless systems; use of divided cross-sections and sloping paths.
• Instrumentation components: transducers, transducer cabling, reflectors, signal timing and processing, signal-to-noise and gain control, self-checking and diagnostics.
• Site and installation: site selection, pre-installation survey (cross-section, velocity distribution, signal propagation), civil works and equipment installation.
• Commissioning and verification: procedures for system commissioning, calibration, routine checks and maintenance.
• Operational requirements: measurement of water stage/depth, channel width and bed level; clock/calendar and data output (local/remote).
• Uncertainty and performance: measurement uncertainty definitions, uncertainty estimation for discharge (including low and high flow considerations), system performance criteria and environmental limits. (See Annex A for uncertainty principles.)

Applications and users

ISO 6416 is intended for practical hydrometry and water management uses that require continuous, accurate flow measurement using ultrasonic transit-time technology:

• Hydrologists and river gauging agencies
• Water resource and flood management authorities
• Environmental monitoring and research institutions
• Utility and industrial water managers (open channels and partly filled conduits)
• Manufacturers and integrators of ultrasonic flow gauging equipment
• Civil and hydraulic engineers designing gauging stations

Typical applications: river and open-channel discharge monitoring, irrigation and drainage canals, weir and channel monitoring where transit-time ultrasonic systems are preferred.

Related standards

• IEC 60041 - covers ultrasonic transit-time technique for full-pipe flow measurement.
• ISO 6416:2017 - reference for transit-time/time-of-flight hydrometry installations and uncertainty estimation.

Keywords: ISO 6416, ultrasonic transit time, time of flight, hydrometry, discharge measurement, gauging station, transit-time method, flow measurement, measurement uncertainty.