Probes Calibration

Dr. Jeffrey Walker

THE UNIVERSITY OF

MELBOURNE

Dept. of Civil and Environmental Engineering

Daniele Biasioni

Field Calibration (tools and method)

HydraProbe equipment Soil sampling

Hyd

ra v

alu

es

(V/V

)%

Water content (V/V)%

HydraProbe

Trend line eq.y = 0.8909x + 2.906

R2 = 0.5688

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measured values

trendline

Field calibration

ThetaProbe

Trend line eq.y = 16.735x + 156.61

R2 = 0.6365

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400

600

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measured values

standart organic calibration

standart mineral calibration

trend line

Th

eta

va

lue

s (m

V)

Water content (V/V)%

Rmse = 9,75 %Rmse = 9,70%

Field calibration per team

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team 1-2

team 3-4

Hyd

ra v

alu

es

(V/V

)%

Water content (V/V)%

HydraProbe

Water content (V/V)%

Th

eta

va

lue

s (m

V)

0

100

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700

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900

1000

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team 1-2

team 3-4

ThetaProbe

Field calibration per farm

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midlothian cullingral roscommon

stanley pembroke merriwa park

illogan dales

Hyd

ra v

alu

es

(V/V

)%

Water content (V/V)%

HydraProbe

0

100

200

300

400

500

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700

800

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1000

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midlothian cullingral roscommon

stanley pembroke merriwa park

illogan dales

Th

eta

va

lue

s (m

V)

Water content (V/V)%

ThetaProbe

Laboratory Calibration

Preliminary preparation of soil sample Adding water

Laboratory Calibration

Putting the samples in oven Theta Probe testingHydra Probe testing

Laboratory Calibration

Weighing of the sample

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Roscommon Stanley

Merriwa Park Dales

Cullingral

Sandy-behaviour-soil farms:Roscommon

Cullingral---------------------------------------

Clay-behaviour-soil farms:Stanley

Merriwa ParkDalesIllogan

MidlothianPembroke

HydraProbe

(farm calibration)

y = -0.0251x2 + 2.061x + 0.5511

R2 = 0.9697

y = 0.7761x - 1.7416

R2 = 0.9842

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Roscommon (sandy)

Stanley

Merriwa Park

Dales

total

Cullingral

trend line (clay soil)

trend line (sandy soil)

HydraProbe

(general calibration)

Lab calibration T=45º

Hyd

ra v

alu

es

(V/V

)%

Water content (V/V)%

Sandy soil farms:

•Roscommon

•Cullingral

-----------------------------------------

Clayey-soil farms:

•Stanley

•Merriwa Park

•Illogan

•Midlothian

•Pembroke

•Dales

Rmse = 8.9%

Rmse = 8.2%

Lab calibration T=45º

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1200

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Pembroke

Midlothian

Illogan

Cullingral

Roscommon (sandy)

Th

eta

va

lue

s (m

V)

Water content (V/V)%

ThetaProbe

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50

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Roscommon

Stanley

Merriwa park

Merriwa values

Hyd

ra v

alu

es

(V/V

)%

Water content (V/V)%

HydraProbe

Calibration relationships

Sandy Soil

Clayey Soil

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Pembroke

Illogan

Cullingral

Merriwa Calibration

Th

eta

va

lue

s (m

V)

Water content (V/V)%

ThetaProbe

Field calibration trend line

Conclusions

Field calibration of the Hydra probe and the Theta probe was

unsatisfactory, due to various errors in the sampling procedure

HydraProbe is highly sensible to the type of soil

ThetaProbe is more stable at extreme values

Further work will include the evaluation of the temperature effect on

the response of the probes

Common errors in NAFE ’05 and possible improvements for NAFE ‘06

Doing 4 measurements around the cylinder and taking the average value

Specific vegetation and soil sampling team

different sampling equipment

Sticking the probe too far from the soil sample Losing soil in the procedure of pushing it out from the

cylinder (clayey soil), or extracting it from the ground (sandy soil)

Bad soil sample labelling on plastic bags or/and on HydraProbe

Swapping of soil sample ID in the drying procedure

SAMPLE

PROBE

Errors

Improvements