Pasport PS-2163 User manual

®
Instruction Manual
012-10646C
PASPORT Soil Moisture Sensor
PS-2163
Introduction
The PASCO Model PS-2163 Soil Moisture Sensor works with a PASCO interface to collect soil moisture
data. The sensor consists of the Soil Moisture Sensor box and the Soil Moisture Probe (cable
assembly).
The sensor measures volumetric water content (VWC) percentage of a soil sample. Volumetric water
content is the volume of soil water per unit of total volume. In simple terms, dry soil consists of solid
Included Equipment Part Number
1. PASPORT Soil Moisture Sensor PS-2163
2. Soil Moisture Probe Cable Assembly (See Technical Support)
Accessory Equipment (See www.pasco.com for details)
PASPORT Soil Water Potential Probe (not included) PS-2513*
Also Required*
PASCO Interface (See www.pasco.com for details)
PASCO Data Collection Software (See www.pasco.com for details)
1
PS-2513 Soil Water
Potential Probe (not
included)
2

®
Soil Moisture Sensor 012-10538C Introduction
2
material and air pockets. A typical volumetric ratio would be 55% solid material
and 45% air pockets. As water enters the soil, the air pockets begin to fill with
water. An example of 10% volumetric water content would be 55% solid
material, 35% air pockets, and 10% water. The maximum volumetric water
content would therefore be 45%. All the air spaces would be filled with water
and the soil would be saturated.
About the Sensor
The Soil Moisture Probe uses capacitance to measure the dielectric permittivity
of the surrounding soil. The volume of water in the total volume of soil most
heavily influences the dielectric permittivity because the dielectric of water (80)
is much greater than the other constituents of the soil (mineral soil, 4; organic
matter, 4; air, 1). Thus, when the amount of water changes in the soil, the Soil
Moisture Probe will measure a change in the capacitance (from the change in
the dielectric permittivity) that can be directly correlated with a change in water
content. Circuitry inside the Soil Moisture Probe changes the capacitance
measurement into a proportional millivolt output.
The Soil Moisture Probe averages the volumetric water content over the entire
length of the probe, with a zone of influence about 2 cm around the probe. The
zone of influence is with respect to the flat surface; there is little or no sensitivity
at the edges of the probe. The electromagnetic field (EM) produced by the
probe decreases with distance from the probe surface.
Installing the Soil Moisture Probe
When selecting a site for installation of the probe, it is important to remember
that the soil adjacent to the probe’s surface has the strongest influence on the
sensor reading. Therefore, any air gaps or excessive soil compaction around
the probe can profoundly affect the readings. Because the probe has a gap
between its prongs, it is also important to consider the size of the media you
are inserting the probe into. It is possible to get sticks, bark, roots, or other
material stuck between the probe prongs, which will adversely affect readings.
Finally, be careful when inserting the probe into dense soil, as the prongs will
break if excessive sideways force is used when pushing them in.
When installing the probe, it is best to maximize contact between the probe and
the soil.
Vertical Orientation
Insert the probe into the soil, making sure that the probe is completely buried at
least 3 cm below the soil surface. The tip of each prong is sharp -
be careful!
The probe may be difficult to insert into extremely compact or dry soil. Carefully
loosen the soil before inserting the probe. Never pound the probe into the soil!
Make sure that there is good contact between the probe and the soil. Use your
fingers and fist to tamp the soil down around the probe.
Horizontal Orientation
The probe can be oriented in any direction. However, orienting the flat side
perpendicular to the surface of the soil will minimize the effects of downward
The copper traces used to measure
water content are sealed between
two pieces of epoxy-impregnated
fiberglass. The electromagnetic
(EM) field generated by the traces
travels through the fiberglass and
into the soil surrounding the probe.
Do not install the probe adjacent to
large metal objects such as metal
poles or stakes. This can attenuate
the probe’s electromagnetic field and
adversely affect output readings.
3 cm

®
PS-2163 012-10538C Setup
3
water movement. The horizontal orientation of the probe makes sure that the
soil moisture measurement is made at a particular soil depth.
Make a narrow trench with a trenching shovel or garden spade. Place the
probe into the narrow trench and completely cover the entire length with soil.
Tamp down the soil along both sides of the probe with your fingers. Cover with
more soil if needed. Repeat the process of tamping down the soil along both
sides of the probe five to eight times.
Removing the Soil Moisture Probe
When removing the soil moisture probe from the soil, do not pull it out of the
soil by the cable! Doing so may break internal components and make the probe
unusable.
Setup
Hardware Setup
The following three steps can be performed in any order.
1. Connect the mini-DIN plug of the Soil Moisture Probe Cable Assembly to
the front end of the Soil Moisture Sensor box.
2. Connect the Soil Moisture Sensor to a PASPORT-compatible interface.
3. If you will be using a computer, connect the PASPORT-compatible
interface to the computer.
Software Setup
Install the latest version of the PASCO data collection software first. Check the PASCO web site at:
www.pasco.com/software
Software Help
See the SPARKvue Help or PASCO Capstone Help for information about
collecting, displaying, and analyzing data.
• In SPARKvue, select the HELP button ( ) in any screen including the
Home Screen.
• In PASCO Capstone, select PASCO Capstone Help from the Help menu,
or press F1.
Do not bend the cable too severely
when putting the probe into the soil.
Let about 10 cm of the cable nearest
to the probe remain straight or gently
curved as shown.
3 cm
10 cm
water movement. The horizontal orientation of the probe makes sure that the
soil moisture measurement is made at a particular soil depth.
Make a narrow trench with a trenching shovel or garden spade. Place the
probe into the narrow trench and completely cover the entire length with soil.
Tamp down the soil along both sides of the probe with your fingers. Cover with
more soil if needed. Repeat the process of tamping down the soil along both
sides of the probe five to eight times.
Removing the Soil Moisture Probe
When removing the soil moisture probe from the soil, do not pull it out of the
soil by the cable! Doing so may break internal components and make the probe
unusable.
Setup
Hardware Setup
The following three steps can be performed in any order.
1. Connect the mini-DIN plug of the Soil Moisture Probe Cable Assembly to
the front end of the Soil Moisture Sensor box.
2. Connect the Soil Moisture Sensor to a PASPORT-compatible interface.
3. If you will be using a computer, connect the PASPORT-compatible
interface to the computer.
Software Setup
Install the latest version of the PASCO data collection software first. Check the PASCO web site at:
www.pasco.com/software
Software Help
See the SPARKvue Help or PASCO Capstone Help for information about
collecting, displaying, and analyzing data.
• In SPARKvue, select the HELP button ( ) in any screen including the
Home Screen.
• In PASCO Capstone, select PASCO Capstone Help from the Help menu,
or press F1.
Do not bend the cable too severely
when putting the probe into the soil.
Let about 10 cm of the cable nearest
to the probe remain straight or gently
curved as shown.
3 cm
10 cm
The mini-DIN plug on the
Soil Moisture Cable
Assembly fits into the
sensor box in only one way.

®
Soil Moisture Sensor 012-10538C Setup
4
SPARKvue
1. Start the SPARKvue software program. If the sensor is connected and
recognized by the software, the SPARKvue Home Screen will show the
name of the sensor (Soil Moisture) and the list of its measurements.
2. Select a measurement such as VWC Potting Soil and click Show.
• A graph display opens with the selected measurement on the vertical axis
and time on the horizontal axis.
3. Touch the Start button to begin collecting data. Later, touch the same
button again to end data collection.
PASCO Capstone
1. Start the PASCO Capstone software program. Click Hardware Setup in the
Tools palette and confirm that the sensor is recognized by the software.
(Click Hardware Setup again to close the window.)
• The Capstone Home Screen shows choices for displaying data.
2. Select a display such as Graph & Digits.
•Page #1 changes to show two Digits displays and one Graph display. Each
display has one or two <Select Measurement> menus.
3. Click the <Select Measurement> menu in one of the displays and select a
choice from the menu. Repeat the process for the other <Select
Measurement> menus in the other displays.
4. Select Record in the Controls Palette to begin collecting data. Later, select
Stop to end data collection.
Calibration
The Soil Moisture Sensor comes pre-calibrated for three soil types: potting soil,
mineral soil, and rockwool. The Soil Moisture Probe is insensitive to variation in
texture and soil conductivity because it operates at a high frequency.
Therefore, its calibrations should apply for all potting soil, mineral soil, and
rockwool.
Other
If the type of soil or media that you are using does not appear in the Unit of
Measure list, you may want to make measurements to create a soil specific
calibration curve yourself, or take advantage of Decagon’s calibration service.
Information on individual probe calibration can be found online at
www.decagon.com/appnotes/echocal.pdf
Information on Decagon’s calibration service can be found at
www.decagon.com/echo/calibration.html.
Creating a Calibration Curve
Volumetric Water Content (VWC) is the ratio of the volume of water per volume
of bulk soil. One way to create a soil specific calibration curve is to match the
Start button
Rockwool is a green fibrous
mat visually similar to
fiberglass insulation used to
grow greenhouse crops in
hydroponics.
The Soil Moisture Probe is
built by Decagon Devices,
Inc., 2365 NE Hopkins Ct.,
Pullman, WA 99163
See the User’s Guides for
the PASCO Data Collection
Software for calibration
instructions.

®
PS-2163 012-10538C Setup
5
voltage output from the Soil Moisture Probe to VWC values for several soil
samples with different degrees of dryness, and then plot a graph of VWC
versus probe output in millivolts (mV).
The basic process is to collect a measured volume of bulk soil, measure its
mass, measure the probe reading in mV for the bulk soil, dry the soil to
determine the amount of water that was in the soil, and calculate the ratio of the
volume of water to the volume of bulk soil. Then, create a graph of VWC versus
probe voltage and determine the “best fit” for the graph. If the graph is linear,
determine the slope and y-intercept. If the graph is quadratic, determine the
coefficients of each term. A
linear calibration curve would have a formula of y =
mx + b where y is the VWC, m is the slope, x is the probe output in mV, and b
is the y-intercept. Finally, create a calculation based on the formula for the soil
specific calibration curve.
Equipment: shovel and bulk soil container, calibration container, Soil Moisture Probe and PASCO
Interface, volumetric soil sampler1, soil drying containers with lids (e.g., baby food jars), scale or
mass balance, drying oven.
Procedure:
1. Collect approximately 4 liters of bulk soil from the depth/location where you
want to measure with the probe.
2. Air dry the soil (spread the soil in a thin layer and use a fan to move air over
the soil.)
3. Remove large objects from the soil and break up large clods so the soil can
fit through a 5 mm mesh.
4. Pack the soil into the calibration container at approximately the field bulk
density.
5. Insert the Soil Moisture Probe fully into the soil. Connect the probe to the
sensor and the sensor to the interface and use the sensor to make a
measurement in
millivolts (mV). Record the measurement.
6. Use the volumetric soil sampler to collect a sample near the probe. Place
the soil sample into a drying container. Measure and record the mass of
the soil sample plus the drying container and then replace the lid on the
drying container*.
7. Wet the calibration soil by adding 200 to 300 milliliters of water to the soil
as evenly as possible. Thoroughly mix the soil.
8. Repeat steps 3 through 7 until the soil approaches saturation. This
generally yields five to seven calibration points.
9. Remove the lids from the drying containers. Dry the volumetric soil
samples in a 105 C oven for 24 hours.
10. Remove the soil drying containers from the oven and replace the lids. Allow
the containers to cool.
11. Measure and record the mass of the dry soil plus the container (without lid).
A quadratic calibration curve would
have a formula of
y = ax
2
+ bx + c
where y is the VWC, x is the probe
output in mV, and
a , b , and c are
coefficients.
*Any water loss due to evaporation
after sampling introduces error to the
volumetric water content calculation.

®
Soil Moisture Sensor 012-10538C Setup
6
Calculations:
1. Determine and record the volume of water by subtracting the dry soil mass
from the “wet” (pre-dried) soil mass. Convert the mass difference into a
volume based on the density of water (1 g/cm3).
2. Calculate and record the volumetric water content by dividing the volume of
water (cm3) by the volume of the soil sample (cm3).
Analysis:
1. Plot volumetric water content versus the sensor voltage output (in mV).
Open a Table display and enter the values for sensor voltage output
(x-axis) and volumetric water content (y-axis).
2. Open a Graph display and use the “Fit” function (PASCO Capstone) or the
“Curve Fit” function (SPARKvue) to find the “best fit” for the plotted data.
Record the slope and the y-intercept. (If the best fit is quadratic, record the
coefficient, a, b, and c.)
3. Create a calculation for VWC based on the slope and the y-intercept (VWC
= mx + b). Let “x” be the sensor voltage output.
Sample Calibration Data
If the best fit is quadratic, create a
calculation for VWC based on the
coefficients, a, b, and c.
VWC = ax2 + bx + c
where
x is the sensor voltage output.
Sensor
voltage output
(mV)
Sample
volume (cm3)
Mass of
container +
moist soil (g)
Mass of
container + dry
soil (g)
Volume of
water (cm3)
VWC (cm3/cm3)
1664 15.31 94.836 94.215 0.621 0.0406
2764 15.31 96.433 95.194 1.239 0.0809
3902 15.31 96.923 94.785 2.138 0.1396
41030 15.31 101.979 98.834 3.145 0.2054
51318 15.31 100.402 95.873 4.529 0.2958
61374 15.31 101.060 95.886 5.174 0.3379
1 A volumetric soil sampler could be a
3 to 5 cm section of metal conduit or
other small diameter (1.5 to 2.5 cm)
metal or thin walled plastic tubing.
Deburr both ends and sharpen one
end for easy insertion into the soil.
Measure its dimensions and calculate
the volume,
Vr2h=

®
PS-2163 012-10538C PASCO Soil Water Potential Probe
7
Experiment Suggestions
• Measure soil moisture over time.
• Evaluate soil moisture content for various species of plants to determine
the optimal level of soil moisture.
• Examine soil moisture content in a greenhouse to determine the amount of
irrigation.
Specifications (PS-2163)
PASCO Soil Water Potential Probe (PS-2513)
Introduction
There are two basic parameters that describe the state of water in soil: one is
soil water content, or the amount of water per unit of soil, and the other is soil
water potential, or the energy state of the water in the soil. Water potential is
often preferred over water content because it shows how water will move in a
soil or from the soil to the plant. In an object comes into hydraulic contact with
soil, the water potential of the object will come into equilibrium with the soil
water potential.
The Soil Water Potential Probe uses a solid matric equilibration technique to
measure the water potential of the soil. The probe has a static matrix - a porous
ceramic disk - that is allowed to reach hydraulic equilibrium with the soil that is
being measured. The probe measures the dielectric permittivity of the ceramic
disk to determine its water potential and thereby the water potential of the soil.
Installing the Probe
Because it measures water potential, the probe needs good hydraulic contact
with the surrounding soil. The preferred method for installing the probe is to
take some native soil, wet it, and pack it in a ball around the entire probe,
making sure that the moist soil is in contact with all surfaces of the ceramic
disk. The probe and moist soil are then packed into the soil at the desired
depth.
After the probe is installed, the hole that was excavated to bury the probe
should be back-filled with care taken to re-pack the soil back to its native bulk
density. Leave at least 15 cm of cable beneath the soil. Do not bend the cable
in a tight radius as it leaves the probe. At least 10 cm of cable nearest the
probe should remain in a straight line.
Sensor Range 0 to 45% volumetric water content in soil
Accuracy ± 4%
Resolution 0.1%
Power 3 mA at 5 V DC
Operating Temperature -40 to + 60 °C
Default Sample Rate 10 samples per second
In the engineering
community, “soil suction”
is used instead of soil
water potential. Soil
water potential is simply
the negative of soil
suction.

®
Soil Moisture Sensor 012-10538C Setup
8
Removing the Probe
When removing the soil water potential probe from the soil, do not pull it out of
the soil by the cable! Doing so may break internal components and make the
probe unusable.
Handling and Care
For the probe to accurately measure water potential, the ceramic disks must
readily take up water. If the ceramic disks are exposed to oils or other
hydrophobic substances, then the ability of the disks to take up water can be
compromised. As much as possible, minimize the exposure of the ceramic
disks to skin oils, synthetic oils, or other hydrophopic compounds.
The probe consists of two engineered ceramic disks sandwiched between
stainless steel screens and the probe’s circuit board. The disks are brittle and
can chip or crack if mishandled. Sharp trauma such as dropping the probe onto
a hard surface can cause the ceramic to break. A cracked ceramic will cause a
loss of accuracy.
Setup
Hardware Setup
The following three steps can be performed in any order.
1. Connect the mini-DIN plug of the Soil Water Potential Probe cable to the
front end of the Soil Moisture Sensor box.
2. Connect the Soil Moisture Sensor to a PASPORT-compatible interface.
3. If you will be using a computer, connect the PASPORT interface to the
computer’s USB port.
Software Help
See the SPARKvue Help or PASCO Capstone Help for information about
collecting, displaying, and analyzing data.
• In SPARKvue, select the HELP button ( ) in any screen including the
Home Screen.
• In PASCO Capstone, select PASCO Capstone Help from the Help menu,
or press F1.
Frozen Soil
Under frozen soil
conditions, the probe
cannot accurately measure
the water potential of soil.
However, the probe is
unaffected by repeated
freeze-thaw cycles, so the
probe can remain in the soil
year round.
The mini-DIN plug on the
Soil Water Potential Probe
cable fits into the sensor
box in only one way.
Calibration
The Soil Water Potential
Probe does not require any
calibration by the user.

®
PS-2163 012-10538C Technical Support
9
Specifications (PS-2513)
Technical Support
For assistance with any PASCO product, contact PASCO at:
Replacement Parts
Contact Technical Support about replacement parts. The Soil Moisture Probe
Cable Assembly description is CBL ASSY SOIL MOISTURE SNS 5M LONG
5P-MDIN.
For more information about the Soil Moisture Sensor and the latest revision of this
Instruction Manual, visit the PASCO Web site at
www.pasco.com/manuals
and enter the product name or number (PS-2163) in the Search text area.
Limited Warranty For a description of the product warranty, see the PASCO catalog or check the
PASCO website at www.pasco.com/legal. Copyright This PASCO scientific Instruction Manual is
copyrighted with all rights reserved. Permission is granted to non-profit educational institutions for
reproduction of any part of this manual, providing the reproductions are used only in their laboratories
and classrooms, and are not sold for profit. Reproduction under any other circumstances, without the
written consent of PASCO scientific, is prohibited. Version 2016-05-03. Trademarks PASCO and
PASCO scientific are trademarks or registered trademarks of PASCO scientific, in the United States
and/or in other countries. For more information visit www.pasco.com/legal.
Product End of Life Disposal Instructions:
This electronic product is subject to disposal and recycling regulations that vary by
country and region. It is your responsibility to recycle your electronic equipment
per your local environmental laws and regulations to ensure that it will be recycled
in a manner that protects human health and the environment. To find out where
you can drop off your waste equipment for recycling, please contact your local
waste recycle/disposal service, or the place where you purchased the product.
Sensor Range -10 to -50 kPa (pF 2 to pF 3.71)
Accuracy ± 5% from -10 to -50 kPa
± 20% of reading from -50 to -500 kPa
Resolution 1 kPa from -10 to -100 kPa
4 kPa from -100 to -500 kPa
Power 25 mA at 2 to 5 V DC
Operating Temperature 0 to + 50 °C
Default Sample Rate 10 samples per second
Address: PASCO scientific
10101 Foothills Blvd.
Roseville, CA 95747-7100
Phone: [phone] (worldwide)
800-772-8700 (U.S.)
Web: www.pasco.com
Email: [email protected]
The probe’s survival
temperature is from
-40 to +50 °C.

®
Soil Moisture Sensor 012-10538C Technical Support
10
The European Union WEEE (Waste Electronic and Electrical Equipment) symbol
(to the right) and on the product or its packaging indicates that this product must
not be disposed of in a standard waste container.