AS 4747.3:2013 Meters for non-urban water supply
4.2 METERING OF PARTIALLY FILLED PIPES
Meters for partially filled pipes include devices for measuring water velocity and height. The output from these devices coupled with the geometry of the meter is used to calculate the flow rate which, when integrated over time, results in measured volume. The height and velocity measurement devices may be one device (for example, a meter incorporating a flow disturbance such as a weir or flume).
Meters for partially filled pipes shall be tested from a minimum height (nominated by the manufacturer) to full pipe condition. Meters shall indicate when flow has occurred below the minimum height specified by the manufacturer. The duration of such flow shall be recorded. If meters for partially filled pipes are not designed to measure under full pipe condition, a visual or audible alarm shall occur and the duration of the full pipe condition shall be recorded.
4.3 MODULAR OPEN CHANNEL METERING SYSTEMS
As outlined in Section 7, modular open channel metering systems may be pattern-approved after assessment against the permissible error limits given in Clause 7.3, or they may be assessed via indirect volumetric calculation for negotiation between the meter owner and licence issuer.
NOTE: An example of the uncertainty measurement for the indirect measurement calculation is given in Appendix C.
During testing, meters and meter modules shall be tested for the effects of influence factors likely to be encountered after installation. The installation instructions shall state limitations of installation, if any.
The installation and putting into service of modular metering systems may involve taking measurements of length, diameter, depth, height, width, angle, time or other quantities. Devices used to make such measurements shall have a certificate from the International Laboratory Accreditation Corporation (ILAC) accredited facility showing the accuracy, uncertainty and traceability of the instruments to Australian Standards of Measurement.
NOTE: In Australia, an ILAC MRA signatory is the National Association of Testing Authority (NATA).