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Automation & Instrumentation in the Irrigation Sector James MacLellan – ABB Limited

Irrigation show, April 2014. Automation & Instrumentation in the Irrigation Sector James MacLellan – ABB Limited. Presentation topics covered. Accurate metering of water use and adherence to legislative requirements Optimising water usage Control of water quality standards

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Automation & Instrumentation in the Irrigation Sector James MacLellan – ABB Limited

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  1. Irrigation show, April 2014 Automation & Instrumentation in the Irrigation SectorJames MacLellan – ABB Limited

  2. Presentation topics covered • Accurate metering of water use and adherence to legislative requirements • Optimising water usage • Control of water quality standards • Mitigation of electrical issues for the wider community • Managing energy efficiency

  3. Accurate metering of water use

  4. What is required? • Consent holders need to provide data regarding water takes. • Flow data needs to be within 5% of a known standard value* *ABB units are OIML R49 Type P.

  5. So which device and why? • Mechanical Meters • Paddle wheel / Turbine / Gear. • Inexpensive& simple. • Accuracy limitations. Moving parts. • Coriolis Flow Meter • Uses principle of inertia for moving mass. • Extremely accurate, minimal install requirements. • Limitation on bore size. Expensive

  6. So which device and why? • Differential Pressure • Bernoulli’s Principle (> speed = < pressure). • Requires a constriction. • Not super ideal for irrigation sector. • Electromagnetic • Magnetic induction. • Without mechanical ‘moving’ parts. • Any ionic electrically conductive fluid.

  7. Optimising water usage

  8. Efficiency = (H2O Transpired / H2O Applied) x 100 Need to obtain some detail as to:- • How much water has been provided to the crop (applied) • How much water is absorbed by the crop (transpired) Need to MEASURE • Rainfall. • Soil depth. • Soil moisture. • Pasture response. • Irrigation application rate and efficiency.

  9. Factors ‘below the surface’.

  10. Efficiency = (H2O Transpired / H2O Applied) x 100 Soil temp @ 10cm depth < 10 deg C: Nil growth. Soil temp @ 10cm depth > 10 deg C: Sun / Moisture. --------------------------------------------------------------------------------- So, measure temperature @ 10cm depth. Crop & Food Research: R.J Martin, S.M.Thomas, R.F. Zykowski AgResearch: D.R Stevens

  11. Instruments & technology in use today

  12. Pt100 & Thermistor (RTD’s) Pt100 • 0.385 ohms per degree C • LINEAR • Accurate • $$$$$$$ Thermistor • Similar principle to Pt100 • NON LINEAR • Not so accurate • Cheap!

  13. Soil moisture content Possible methods:- • Capacitance • Resistance • Conductivity • Temperature Most common:- • Time Domain Transmission • Electrical pulse • Time / size affected by surrounding media

  14. Time Domain Transmission • Conditions constant. • Repeatable result. • Imagine the wall changes… • The speed, time & force of the returning ball will very. • Alter one ‘constant’. • Results vary • Moisture change = change in pulse signal properties

  15. The Electro-Magnetic Flow Meter • 3rd Law of induction (1832). • Left Hand Rule (motors). • mV signals generated • Electro-magnetic field ‘switches’. • mV signal size proportional to flow.

  16. Control of water quality standards

  17. Chemical analysis… • pH (measure of acidity / alkalinity) • Conductivity (measure of ionic concentration) • Turbidity (measure of the particulates)

  18. pH / Conductivity / Turbidity

  19. Nitrate & Dissolved Oxygen Analysis • Leaching • Human health issues • Death of fish & marine species • Affect soil nutrition (< Ca) • Reduced by decomposition of organics (>BOD) • Affect aquatic species

  20. Mitigation of electrical issues& managing energy efficiency

  21. Instruments: Delicate / Fragile / Fine / Precise

  22. Getting the WaterThe crowded room • Energy required to ‘lift’ or ‘pump’ water. • Most efficient use of electrical energy via VSD / VFD.

  23. Variable Speed Drives (VSD / VFD) • Extremely efficient devices with regard to power use. • ‘Raw’…VSD’s can cause huge power issues across networks and disrupt/distort instrument signals • If you install them 100%...The instrumentation guy is happy…Everybody is happy

  24. Sending the signalsMiscommunications

  25. Common issues – Missing data Conventional • Flow data via pulses. • Telecommunication fail. • Pulses / units disagree. • Punch up. Serial communication • Flow data via digital comms • Receiver reads instrument value from a register • Doesn’t matter if communications are intermittent • MODBUS

  26. Energy Efficient Devices

  27. Le Chatelier’s Principle

  28. What we don’t want to see….

  29. “Before you rip down a fence, think for a moment why it was put there in the first place”

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