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Background - Portable Moisture Probes

New soil moisture sensors Enable high performance SWAT Controllers Mike van Bavel, President Dynamax Inc. - Our Mission. Combine science and technology to produce advanced & affordable soil moisture irrigation control solutions for efficient water management and water conservation.

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Background - Portable Moisture Probes

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  1. New soil moisture sensors Enable high performance SWAT ControllersMike van Bavel, President Dynamax 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

  2. 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

  3. 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.

  4. 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 accurate, when you use accurate and proven sensors. • The answer is: soil moisture is what the plants use and people intuitively understand how it works.

  5. 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

  6. SM200 specifications ½” Thread For conduits Water tight connector Durable plastic body 2.5mm pins 50mm long Stainless steel – indefinite lifespan Shaped pin termination

  7. SM200 Specifications

  8. 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.

  9. Soil Moisture Control –Set Point Requirements Set Point

  10. 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.

  11. 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

  12. What Sensor Accuracy do We need ? Clay Sand 60% Wasted Water Over Irrigated Over Irrigated 50% Wasted Water & Fertilizer Field Capacity (45%) Optimum Growth Moisture Range 40% Irrigation Start Point (33%) Stress Level < 33% Deficit Irrigated 30% 20% Wilting Point 22% Dead Plants - No Production Field Capacity (10%) Optimum Moisture Range 10% Irrigation Start (7%) Stress Level < 7% 0% Maximum Error Allowable +/ – 3 % WIlting Point 4%

  13. Real Time Example - Seattle

  14. 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.

  15. CIT SWAT Test Results

  16. The range of 95% confidence, (2*SD) = +/-1.4%. Well within the minimum accuracy needed to control moisture in sandy soils.

  17. Advanced Moisture Level Control 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.

  18. IL200-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.

  19. 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

  20. 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.

  21. New - Advanced Irrigation Control with SM200, GP1 Precision Moisture control and monitor with recordings: Soil moisture, water used, rainfall, temperature

  22. 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!

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