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April 2007
New soil moisture sensors New soil moisture sensors Enable high performance SWAT Enable high performance SWAT
ControllersControllersMike van Bavel, President Mike van Bavel, President
Dynamax Inc. - Our MissionDynamax Inc. - Our Mission • Combine science and technology to produce
advanced & affordable soil moisture irrigation control solutions for efficient water management and water conservation.
• Delta-T Devices (UK)} sensor design and production
• Dynamax Inc (Houston) } system design, controls manufacturing, USA sales / support
April 2007
Background - Portable Moisture Probes
• Multiple soil moisture readings
• Battery operated hand held
recorder & display – HH2
• ThetaProbe soil moisture sensors
• Portable Sensors
- Surface readings
-or inserted in access tubes
-Profile Probes
• Irrigation system audits, test application, and soil surveys for salinity (EC) – electrical conductivity
April 2007
New Conservation Controllersvs Plain Old Timer
• There are 2 basic conservation controller types:– Soil Moisture Sensor:
• Uses actual soil conditions for irrigation start / stop points.
• Uses real-time information on soil moisture conditions for irrigation. Regulates a Timer according to water needs.
– ET (Evapotranspiration):
• Uses historical / pre-programmed water usage, or actual ET from a local station or the controller, updated manually or automatically.
• Regulates a timer according to estimated water use.
• The plain old timer has no feedback on the actual soil or the weather conditions.
April 2007
Why Soil Moisture ?• Properly applied soil moisture irrigation
scheduling is the most accurate and efficient conservation method!
• Both technologies work for water conservation but soil moisture is the most most accurate, when you use accurate and accurate, when you use accurate and proven sensors.proven sensors.
• The answer is: soil moisture is what the plants use and people intuitively understand how it works.
April 2007
SM200 Introduction• Low cost• Good accuracy• Excellent temp stability• Excellent salinity response• Durable• Buriable• Compact for limited space
applications• Patented design• Proven Delta-T technology
April 2007
SM200 specifications
Water tight connector
½” ThreadFor conduits
2.5mm pins 50mm longStainless steel –
indefinite lifespan
Durable plastic body
Shaped pin termination
April 2007
SM200 SpecificationsPower 5 to14 V @15mA typically, low power
Output 0 to 1.2V full scale, easy to read
Range 0 to 40% accuracy 3%
Range 0 to 60% accuracy 5%
Add. Temp errors
0.01%/ C over 0 to 40%, 0 to 60 C
Add. Salinity errors
3.5% over 0 to 40%, to 500mSm-1
April 2007
Why are Delta-T SM200 Soil Moisture Sensors Accurate and Reliable?
• Developed by Scientists and produced for scientists (since 1996). Wide range of applications needed for research.
• The first FDR probe with a single voltage output - ThetaProbe patented technology.
• FDR - (Frequency Domain Reflectometer) Measures soil dielectric with a microwave signal. Wide moisture range 0-60%.
• Operates with a wide range of soils, and includes a calibration built into each and every sensor.
• Salinity and temperature instability are designed out, and have limited effects.
April 2007
Soil Moisture Control –Soil Moisture Control –Set Point RequirementsSet Point Requirements
Yellow Zone - Deficit Irrigation Green Zone - Optimum Growth Range
45%
40%
28%29%
32%
36%
30%
27%
10%
21%
16%
7.0%
11.5%
15.0%
19.5%
22.5%
28.0%
25.0%23.5%
21.5%
30.0%
33.0%
22%
20%
15%
18%18%20%
15%
12%
4%
9%
7%
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
50%
1) Sand 2) LoamySand
3)SandyLoam
4)Loam 5)Silt Loam 6)SandyClay Loam
7)SandyClay
8)ClayLoam
9)SiltyClay Loam
10)SiltyClay
11)Clay
Soil Type
% W
ate
r b
y V
olu
me
Field Capacity(Ratcliff 1983)
Irrigation StartPoint
Wilting Point
Field CapacityWater Above this Line is
Wasted - Run-off
Wilting PointPlants Unable to Take Up Water
M.A.D - IrrigationStart Point
Set Point
April 2007
Moisture Control theory and requirements
•A closed-loop controller (C) uses feedback (-) from sensors to control states or outputs of a dynamical system (y).
• The reference values ( r +) are set by the user to a desired beneficial level.
•A operational controller must also have: Stability, Controllability, and Observability.
• Sensor feedback that has error in excess of the desired control function feedback (e), causes uncontrollability and problems with observability.
April 2007
Closed Loop Controllers- The good news:
Advantages over open loop, ex. timers:• disturbance rejection • guaranteed performance even with model uncertainties, when the model structure does not match perfectly the real process and the model parameters are not exact • unstable processes can be stabilized • reduced sensitivity to parameter variations • improved reference tracking performance
April 2007
What Sensor Accuracy do We need ? What Sensor Accuracy do We need ?
Stress Level < 7%
Irrigation Start (7%)
Stress Level < 33%
Deficit Irrigated
Clay Sand
0%
10%
30%
40%
50%
Field Capacity (10%)
WIlting Point 4%
Over Irrigated
Optimum GrowthMoisture Range
Optimum Moisture Range
Wilting Point 22%
Dead Plants - No Production
Wasted Water & Fertilizer
Irrigation Start Point (33%)
Field Capacity (45%)
Over Irrigated
20%
60%
Maximum Error Allowable +/ – 3 %
Wasted Water
April 2007
Real Time Example - Seattle
April 2007
CIT SWAT Testing protocol - Results
• What does the test result show us?• A correlation between a soil simulator drying
out and a soil moisture sensor reading in the top 4 inches. (not a calibration for the sensor)
• The soil drying trend will show a correlation to the soil sensor in a single installation to be accurate enough for control purposes.
• If there are poor correlations due to salinity effects or temperature operating range changing the sensor characteristics.
April 2007
Correlation of all data with weight loss vs all Delta -T SM200 Sensor readings
y = 1.0253x
R2 = 0.9104
0%
10%
20%
30%
40%
50%
60%
0% 10%
20%
30%
40%
50%
60%
Calculated water content %
Sen
sor
Mo
istu
re c
on
ten
t %
"Overall Soil Texture"
Linear fit for Sensor Measurements vs. Calculated Water Content
Zero Intercept
Linear ("Overall Soil Texture")
April 2007
CIT SWAT Test ResultsAll Salinity Levels Compared On Medium Texture Soil
y = 0.8368x + 0.0417
R2 = 0.9776
y = 0.8077x + 0.0572
R2 = 0.9959
y = 0.9157x + 0.0427
R2 = 0.9815
y = 0.9181x + 0.0199
R2 = 0.95360%
5%
10%
15%
20%
25%
30%
35%
40%
45%
50%
0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50%
Gravimetric Readings
Se
ns
or
Re
ad
ing
s
6.4.1 - 1.0 dS/m
6.4.2 - 1.5 dS/m
6.4.3 - 3 dS/m
6.2.2
Linear (6.4.1 - 1.0 dS/m)
Linear (6.4.2 - 1.5 dS/m )
Linear (6.4.3 - 3 dS/m)
Linear (6.2.2)
April 2007
6.2.3 Delta-T SM200 Rep1Sensor Measurement vs Calculated Volumetric Water
Coarse Textured Soil
y = 0.9x + 0.0289
R2 = 0.9922
0%
10%
20%
30%
40%
50%
60%
0%
10
%
20
%
30
%
40
%
50
%
60
%
Calculated water content %
Sen
so
r M
ois
ture
co
nte
nt
%
6.2.3 Calibration in a CoarseTextured Soil
Upper Limit
Lower Limit
Linear fit for SensorMeasurements vs.Calculated Water Content
The range of 95% confidence, (2*SD) = +/-1.4%.Well within the minimum accuracy needed to control moisture in sandy soils.
April 2007
Advanced Moisture Level Advanced Moisture Level Control IL200-MCControl IL200-MC
• How does it work? – Set desired initial
Irrigation Start Point (% Vol) by soil type chart.
– The output relay triggers when below the set point.
• Or use a learning curve– Determine site specific
field capacity one day after irrigation.
– Adjust the moisture to the ISP, about 0.9 * field capacity.
April 2007
IL200-MC Irrigation System ApplicationsIL200-MC Irrigation System Applications • Satellite and Standard Timer Upgrade Scheduling:• IL200-MC controls the water for 5-8 zones grouped together. • The moisture sensor, SM200, is buried in most critical zone. • Valve power is enabled when moisture is below the irrigation set
point.
April 2007
Moisture ClikTM Setup
• The setup is fairly simple.
• There are only three connections to be made after the box is mounted.
• The basic steps are:– Connect the power lead.
– Connect the sensor leads.
– Connect the output / control wires from the relay to the sensor input.
– Other applications• Direct Valve Control
• Common Interrupt line
• Alarms to central control
April 2007
Set the Dial for the Irrigation Start
• Set by Soil Type Directly, or
• Irrigate and adjust by Soil Field Capacity
• Timer Program - - Short cycles, with multiple start times:
Repeat water & soak so all zones are the same soil moisture.
April 2007
New - Advanced Irrigation Control with SM200, GP1
Precision Moisture control and monitor with recordings:
Soil moisture, water used, rainfall, temperature
April 2007
Conclusions • Accurate water conservation control
solutions with soil sensors are available.
• Smart water solutions may be successful with tested sensors.
• Next: Develop the protocol to measure savings and water efficiency certification.
• Thank you for attending, Dynamax appreciates your time and interest!