5 Field Testing
The development period for the prototype meter coincided with the winter months and therefore it was not possible to gain access to an operating irrigation system to field test the meter. Instead, advantage was taken of Lincoln Environmental’s involvement with an experimental sprinkler frost protection system to provide a suitable test installation. The advantages of this particular installation were:
- Detailed design information was available for the system;
- The system was heavily instrumented and parameters such as operating pressure and operating times were already being monitored;
- The site was visited regularly as part of the original research programme;
- The system represents (on a small scale) a typical horticultural irrigation block, and
- The environment was expected to be harsh.
5.1 CALIBRATION
Accurate information on the actual design of the installation was readily available. The IRRICAD™ design program was then used to analyse the system performance in terms of flow for a wide range of pressures downstream of the control valve. This analysis provided the data for the lookup table required enabling the meter to convert pressure measurements to flow rate and to total volume used.
5.2 INSTALLATION
The pressure sensor was installed downstream from the control valve at the same location as the existing (and separately monitored) pressure sensor used as part of the control system for the frost protection experiment. The flow meter itself was mounted on a stake adjacent to the sensor. The installation mimics that which would be used if the meter were being used for monitoring the flow into a typical orchard block.
5.3 PERFORMANCE
Early results suggest that the flow meter is performing adequately in terms of converting system pressure to current flow rate and total flow volume. Some minor problems with the software in terms of its robustness to operator error and error checking and some cosmetic (but important) details of the user interface have been identified. These problems are relatively easy to overcome, and other than re-programming the microprocessor, do not require any physical change to the basic concept of the meter. This test will continue until the end of the frost protection ‘season’ (late October) when the software will be upgraded and the unit transferred to monitor the performance of a more conventional irrigation system.
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