PASCO PS-2163 User Manual

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Instruction Manual

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PS-2513 Soil Water

Potential Probe

(not included)

2

012-10646A

PASPORT Soil Moisture Sensor

PS-2163

Included Equipment Part Number

1. PASPORT Soil Moisture Sensor PS-2163

2. Soil Moisture Probe Cable Assembly 514-10696

Accessory Equipment (See the PASCO Catalog for details)

PASPORT Soil Water Potential Probe (not included) PS-2513*

Compatible PASPORT Interfaces (See the PASCO Catalog for details)

Xplorer PS-2000

PowerLink PS-2001

Xplorer GLX PS-2002

SPARK Science Learning System PS-2008

SPARKlink PS-2009

USB Link PS-2100

*See the PASCO catalog or visit the PASCO web site at www.pasco.com
for more information about the PS-2513 Soil Water Potential Probe.

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Soil Moisture Sensor Introduction

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

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
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 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.

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Model No.PS-2163 Setup

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.

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 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 interface.

3. If you will be using a computer, connect the PASPORT interface to the com-

puter’s USB port.

DataStudio Setup

If you will be using the Soil Moisture Sensor with a computer, install the latest version of
DataStudio first. Check the PASCO web site at www.pasco.com for informa­tion.

1. When you connect the Soil Moisture Sensor to the computer
through a PASPORT interface, the PASPortal window will
launch automatically (if DataStudio is not already running).

2. Select Launch DataStudio in the PASPortal window.

A Digits display for volumetric moisture content (% VWC) will appear. The
default is for Potting Soil.

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