© abb | slide 1 automation & instrumentation in the irrigation sector james maclellan – abb...
TRANSCRIPT
© ABB| Slide 1
Automation & Instrumentation in the Irrigation SectorJames MacLellan – ABB Limited
Irrigation show, April 2014
January 2014
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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
Month DD, YYYY
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Accurate metering of water use
Month DD, YYYY
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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.
Month DD, YYYY
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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
Month DD, YYYY
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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.
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Optimising water usage
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Efficiency = (H2O Transpired / H2O Applied) x 100
Need to obtain some detail as to:-
1. How much water has been provided to the crop (applied)
2. How much water is absorbed by the crop (transpired)
Need to MEASURE
3. Rainfall.
4. Soil depth.
5. Soil moisture.
6. Pasture response.
7. Irrigation application rate and efficiency.
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Factors ‘below the surface’.
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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.
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So, measure temperature @ 10cm depth.
Crop & Food Research: R.J Martin, S.M.Thomas, R.F. Zykowski
AgResearch: D.R Stevens
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Instruments & technology in use today
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Pt100
0.385 ohms per degree C
LINEAR
Accurate
$$$$$$$
Thermistor
Similar principle to Pt100
NON LINEAR
Not so accurate
Cheap!
Pt100 & Thermistor (RTD’s)
Month DD, YYYY
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Possible methods:-
Capacitance
Resistance
Conductivity
Temperature
Soil moisture content
Most common:-
Time Domain Transmission
Electrical pulse
Time / size affected by surrounding media
Month DD, YYYY
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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
Time Domain Transmission
Month DD, YYYY
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3rd Law of induction (1832).
Left Hand Rule (motors).
mV signals generated
Electro-magnetic field ‘switches’.
mV signal size proportional to flow.
The Electro-Magnetic Flow Meter
Month DD, YYYY
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Control of water quality standards
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pH (measure of acidity / alkalinity)
Conductivity (measure of ionic concentration)
Turbidity (measure of the particulates)
Chemical analysis…
Month DD, YYYY
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pH / Conductivity / Turbidity
Month DD, YYYY
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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
Month DD, YYYY
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Mitigation of electrical issues & managing energy efficiency
Month DD, YYYY
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Instruments: Delicate / Fragile / Fine / Precise
Month DD, YYYY
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Getting the WaterThe crowded room
Energy required to ‘lift’ or ‘pump’ water.
Most efficient use of electrical energy via VSD / VFD.
Month DD, YYYY
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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
Variable Speed Drives (VSD / VFD)
Month DD, YYYY
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Sending the signalsMiscommunications
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Conventional
Flow data via pulses.
Telecommunication fail.
Pulses / units disagree.
Punch up.
Common issues – Missing data
Serial communication
Flow data via digital comms
Receiver reads instrument value from a register
Doesn’t matter if communications are intermittent
MODBUS
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Energy Efficient Devices
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Le Chatelier’s Principle
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What we don’t want to see….
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“Before you rip down a fence, think for a moment why it was put there in the first place”
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