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!