New soil water tension sensors: the dihedral and IG sensor

New soil water tension sensors: the dihedral and IG sensor

New soil water tension sensors: the
dihedral and IG sensor
Carlos M. P. Vaz
Adonai G. Calbo
Embrapa Agricultural Instrumentation
São$Carlos,$SP$
Monitoring soil water content
-  Agriculture - soil management practices
-  Irrigation
-  Hydrological modeling - watershed and regional
-  Drought forecasting modeling
-  Landslide studies
-  Weather station networks for Climate change studies
Soil water remote sensing
spaceborne
airborne
ground
Point sensors - Direct field instrumentation
Neutron probe
TDT#
gypsum block
TDR
Capacitance, Inductance (FDR)
Wireless sensor network
Precision Agric (2015) 16:216–238
225
Fig. 2 Architecture of the soil moisture real-time monitoring system (Zhang et al. 2012)
-  Low cost sensors
content, signal attenuation and bit error rate are minimal. The path loss is also influenced
-  Low energy consumption
by depth of the WUSN.
In the authors’ test model, sensors are buried at depths of 0.8, 1, 1.6 and 2 m, which
implies a large power
requirement.
The UG nodes would have to expend a lot of
-  source
Little
maintenance
energy in a single-hop to transmit data to the sink node located aboveground. Thus the
nodes power sources could deplete quickly thereby shortening the network lifetime.
Soil water sensors
Soil%water%potential% Soil%water%content%
!
Technique!!
Neutron%probe%
TDR%
TDT%
Limitation!
ionizing%rad.%
complex%
design%
salinity,%
temperature%
Range!
dry6saturated%
dry6saturated%
dry6saturated%
Dual%needle%
relatively%new%
dry6saturated% low%
Tensiometer%
maintenance%
up%to%80%kPa%
FDR%
Cost!
high%
high%
moderate%
dry6saturated% moderate%
low%
salinity,%
Granular%Matrix%
temperature%
up%to%200%kPa% low%
6%resistivity%
lower%accuracy%
Ceramic6FDR%
calibration%
dry6saturated% low%
Use of soil water sensors in Brazil
Number'of'papers'
Sensor'
Brand'
90’' 00’' 10’' total'
Tensiometer*
Home,made,*Irrometer*
8* 29* 27* 64'
TDR*
TDR100,*Trase,*1502*
1* 25* 24* 50'
Theta*Probe,*CS616,*Hydrosense,*
*
*
*
FDR*
5TE,*Diviner*2000,*MP,917,*Hydra* 0* 20* 14* 34'
Probe,*Environscan,*Hydrofarm*
Neutron*probe* CPN,*Troxler*
6* 12* 8*
26'
Resistivity*
Watermark,*Bouyoucos*Block*
1*
5*
5*
11'
Developing new soil water sensors
-  National, low cost sensors
-  Greenhouse, garden
-  Drip irrigation control
-  Sensors for wireless network – site specific
irrigation (VRI)
-  Technical tensiometers – Research
Irrigás
A.G. Calbo e W.L.C
Water#tension#(kPa)#
508
Bubbling#pressure#(kPa)#
Figure 5. Soil water tension in which irrigas porous cups featuring
cup
ten
wit
the
Thi
con
inc
con
wa
fav
The
ran
con
por
197
and
12
per
Dihedral tensiometer
60
50
h (cmH2O)
spacer (a0)
tgα=a/200)
/200
tgα=a
0 0
40
a0=0,1mm
30
20
0,5mm
1mm
2mm
10
0
0
5
10
15
20
25
30
L (cm)
vertex
Young-Laplace equation
R
ri
P0
θ"
α"
Pi
γ
P0 −Pi =
R
!
r
R=
(1)$
i
(
cos α + θ
)
(2)$
Pi = −
!
(
)
cos α + θ γ
ri
2γ
Pi = −
ai
(4)$
(3)$
a0
L=5cm
Dihedral tensiometer Publications
CALBO$A.G.$2011.$Dihedral$sensor$for$determining$tension,$potenAal$and$
acAvity$of$liquids.$Brazilian$Agricultural$Research$CorporaAon.$Patent#
number:$WO$2011/079367$A1$
$
VAZ,$C.M.P.,$A.G.$CALBO,$L.F.$PORTO,$L.H.$PORTO.$2013.$Principles$and$
applicaAons$of$a$new$class$of$soil$water$matric$potenAal$sensors:$the$
dihedral$tensiometer.$Procedia#Environmental#Sciences,$19:484X493$
$
VAZ,$C.M.P.,$A.G.$CALBO,$L.F.$PORTO.$2012.$EvaluaAon$of$a$portable$
dihedral$tensiometer$designed$to$measure$water$tension$in$substrates.$SSSA$
InternaAonal$Annual$MeeAng,$Tampa,$FL$
$
VAZ,$C.M.P.,$A.G.$CALBO,$L.F.$PORTO.$2012.$Measuring$soil$water$tension$
with$a$staAonary$dihedral$tensiometer:$Principles$and$applicaAons.$SSSA$
InternaAonal$Annual$MeeAng,$Tampa,$FL$
20
0
10
20
30
40
50
Time (min.)
30
40
S3
35
25
30
kPa
25
20
L (mm)
Li (mm)
8.6 kPa
13.1 kPa
15
18.6 kPa
10
20
15
10
5
5
0
40
80
120
0
160
0
10
50
40
30
20
10
0
20
30
ψapplied (kPa)
Time (min.)
ψdihedral (kPa)
60
RMSD = 1.4 kPa
0
10
20
30
ψapplied (kPa)
40
50
40
50
Summary and Conclusions
-  Easy construction and test
-  Low cost sensors
-  Relatively large range of WP measurements
-  Relatively fast response time (5-40 min.)
-  No air cavitation problems (low maintenance)
-  Effect of colloids and salts on the glass surface
-  Effect of temperature and salinity (contact angle)
-  Visual (electric, optics, pneumatic transduction)
-  Most glue or resin are water soluble
IG - Light reflection on glass beads sensor
PT
glass
beads
light
voltage
voltage
LED
water tension
IG - Light reflection on glass beads sensor
glass
beads
!
porous
cup
lid
phototransistor
Electronic
circuit board
LED
IG sensor Publications
CALBO,$A.G.,$C.M.P.$VAZ,$W.A.$MAROUELLI,$L.F.$PORTO.$2013.$Water$
tension$sensor,$system$for$characterizing$and$conAnuously$measuring$soil$
water,$system$for$indicaAng$criAcal$soil$water$tension$and$irrigaAon$rod.$
Patent#number:$WO$2014172765$A1.$2$
$
CALBO,$A.G.,$C.M.P.$VAZ,$L.F.$PORTO.$2014.$A$porous$cup$sensor$to$measure$
soil$water$tension$by$light$reflecAon.$SSSA$InternaAonal$Annual$MeeAng,$
Long$Beach,$CA$
$
CALBO,$A.G.,$C.M.P.$VAZ,$L.F.$PORTO.$2014.$Sensor$de$água$no$solo$por$
reflexão$de$luz$em$Pparcculas$de$vidro$com$granulometria$controlada.$
Simpósio$Nacional$de$Instrumentação$Agropecuário,$SIAGRO$2104,$São$
Carlos,$SP$$
$
7
6.5
6.0
200-250 µm
5.5
65
6
17 kPa
sensor (volts)
sensor (volts)
33
9 kPa
5.0
4.5
4.0
5 kPa
3.5
1 kPa
3 kPa
0
20
40
60
tempo (min.)
80
100
5
200-250 µm
4
3
0
10
20
30
40
50
60
tensao da agua (kPa)
70
80
4.0
4.0
3.5
5 kPa
3.5
50-100 µm
3 kPa
9 kPa
1.5
17 kPa
1.0
4.0
33 kPa
0.5
3.5
0.0
3.0
sensor (volts)
sensor (volts)
2.5
2.0
0
76 kPa
50-100 µm
3 kPa
9 kPa
1.5
17 kPa
1.0
33 kPa
0.5
0.0
76 kPa
65 kPa
0
50 100 150 200 250 300 350 400
tempo (min.)
2.0
1.5
1.0
4.0
0.0
3.0 0
50 100 150 200 250 300 350 400
tempo (min.)
2.5
0.5
3.5
65 kPa
5 kPa
2.5
2.0
50-100 µm
3.0
sensor (volts)
sensor (volts)
3.0
10
20
50-100 µm
30 40 50
60
70
80
70
80
tensao da agua (kPa)
2.5
2.0
1.5
1.0
0.5
0.0
0
10
20
30
40
50
60
tensao da agua (kPa)
9.9
9.9
3 kPa
< 50 µm
< 50 µm
9.8
sensor (volts)
5 kPa
9 kPa
9.7
17 kPa
33 kPa
9.6
65 kPa
9.9
9.5
3 kPa
0
20
40
sensor (volts)
9.8
60
80
<100
50 µm
120
140
9.8
5 kPa
9 kPa
17 kPa
33 kPa
9.6
9.6
9.5
tempo (min.)
9.7
9.7
9.9
76 kPa
87
sensor (volts)
sensor (volts)
9.8
< 50 µm
0
20
40
60
80
potencial da agua (kPa)
9.7
9.6
65 kPa
87 kPa
9.5
0
20
40
60
80
100
tempo (min.)
120
140
9.5
0
20
40
60
potencial da agua (kPa)
80
parallel
angle
L#
coarse
fine
How to bind the GB particles?
-  Sintering (600 °C)
-  Sodium silicate (300 °C)
+
Na2(SiO2)nO
+
Waterglass
Liquid glass
300 °C, 30 min.
wet
dry
Surface smoothed with fine sand paper
Measurements in soil
mixture MX1 (coarse)
250-200 μm (20%)
200-150 μm (20%)
150-100 μm (20%)
100 - 50 μm (20%)
< 50 μm (20%)
< 50 μm (fine)
10-50 μm (98%)
< 10 μm (2%)
MX1
tensiometer
IG sensor
TDR
voltmeter
MX1
IG voltage vs WC/WP inside the sensor
IG voltage vs WC/WP - MX1
0.4"
water&content&(m3&m-3)&
IG#sensor#(volts)#
8"
7"
6"
5"
4"
0"
20"
40"
60"
80"
0.3"
0.2"
0.1"
0"
0"
100"
6.5"
6"
6"
IG#sensor#(volts)#
IG#sensor#(volts)#
6.5"
5"
4.5"
4"
0"
5"
10"
15"
water#tension#(kPa)#
20"
40"
60"
80"
100"
Time&(min)&
Time#(min.)#
5.5"
20"
5.5"
5"
4.5"
4"
0"
0.1"
0.2"
0.3"
water#content#(m3#m33)#
0.4"
NEXT STEPS
-  Evaluate finer mixtures (< 50 μm and finer) in soils
-  Test reproducibility
-  Improve sensor design:
resin
glass plate
GB
GB
-  Test infrared LED (near and short wavelength: 0.75-3μm)
-  Evaluate transmission mode:
GB
glass
plate