Spectrum FIELDSCOUT TDR 100 Product Manual

TDR 100

®

Soil Moisture Meter

PRODUCT MANUAL

Item # 6440FS

(ES) Equipements Scientifiques SA - Département Bio-tests & Industries - 127 rue de Buzenval BP 26 - 92380 Garches

Tél. [phone] - Fax. [phone] - e-mail: [e-mail] - Site Web: www.es-france.com

CONTENTS

General Overview 3
Probe Dimensions 3

Meter Operation 4
Volumetric Water Content Mode 6
Relative Water Content Mode 8
Identifying the Correct Com Port 9
Connecting to a PC/Changing Batteries 10
Main Toolbar 11
Meter Settings 12
Meter Calibration 14
Specifications 15
Appendix 1: Soil-Specific Calibration 16
Appendix 2: Checking VWC Readings 18

Appendix 3: Troubleshooting 19

This manual will familiarize you with the features and operation of

your new Field ScoutTM TDR Soil Moisture Meter. Please read this

manual thoroughly before using your instrument. For customer

support, or to place an order, call Spectrum Technologies, Inc. at

[phone] or [phone]

between 7:30 am and 5:30 p.m. CST

FAX [phone]

e-mail: [e-mail].

www.specmeters.com

2

General overview

Thank you for purchasing the Field ScoutTM TDR Soil
Moisture Meter. This manual describes the features and
operation of the meter.

Soil moisture is a critical and, potentially highly variable
component of the soil environment. Time-domain reflec­tometry is a proven technology for quickly and accurately
determining volumetric water content (VWC) in soil.

The Field Scout probe allows the user to easily and rapid­ly take many measurements. The user can quickly transi­tion between taking VWC readings in standard and high­clay mode. Through the software, the user can program
relative water content modes for multiple sites.

Probe Dimensions

3.0”

3.1”

1.3”

3

Meter Operation

ON

measurement period). The data screens for the Water

Content Modes are explained on pages 8 and 10. The Peri­od mode is used for doing soil-specific calibrations and is
explained on page 14.

Battery at 85%
Firmware V5.0

Sample meter power-up
and data screens

The ON switch turns the meter on and
off. When the meter is turned on, it will
display the battery status for 3 seconds.
The screen will then display the most
recently used MODE screen
(Volumetric or Relative water content or

Stndrd VWC%=27.1
PL=M N008 A=26.5

Period = 0950 uS
N015

READ

Delete

Clr Avg

MODE

Press the READ button to read the probe
and update the screen values. The data
point can be cleared from memory with
the DELETE/CLR AVG button (below).

When the DELETE/CLR AVG but­ton is pressed and immediately re­leased, the last data point will be re­moved from the running average.
Pressing and holding this button will
reset the running average.

Pressing the MODE button allows the
user to determine the type of measure­ment that will be taken or select the
length of rods connected to the probe.

4

Data Measurement Modes
Available measurement options are volumetric water con­tent (VWC) using the standard or high clay mode (see p.

8), up to two relative water content modes (see p. 10), or
measurement period (in microseconds). Relative water
content options will only appear if they are configured in
the software (see Meter Settings, p. 12). The period meas­urement is available for users interested in performing soil

-specific calibrations (see Appendix 1).

Changing Rod Length

ROD=MED (4.7in)

In order to get accurate volumetric or relative water con­tent (VWC or RWC) readings, the rod length setting must
be correct. In the VWC modes, the currently selected rod
length appears in the lower left corner of the LCD screen.
The options are Turf (1.5”), Short (3.0”), Medium (4.7”),
and Long (7.9”) rods. Press the MODE button until the
LCD displays the rod length options screen. Pressing the
DELETE/CLR AVG button will allow you to toggle be­tween the three choices.

Meter Calibration Mode
This mode allows you to calibrate the meter. The calibra­tion procedure is performed in air and distilled water (see

HIT DEL To Chnge

Rod Length Options Screen

Meter Calibration, p. 6). Requires firmware v. 6.5 or
greater.

CALIBRATION MODE

HIT READ To Cal

Meter Calibration Screen

5

Volumetric Water

Content Mode

The volumetric water content (VWC) is the ratio of the
volume of water in a given volume of soil to the total soil
volume. At saturation, the volumetric water content
(expressed as a percentage) will equal the percent pore
space of the soil.

The underlying principal of TDR involves measuring the
travel time of an electromagnetic wave along a wave­guide. The speed of the wave in soil is dependent on the

bulk dielectric permittivity (ε) of the soil matrix. The fact
that water (ε = 80) has a much greater dielectric constant
than air (ε = 1) or soil solids (ε = 3-7) is exploited to de-

termine the VWC of the soil. The VWC measured by
TDR is an average over the length of the waveguide.

Electronics in the TDR 300 generate and sense the return
of a high energy signal that travels down and back,
through the soil, along the waveguide composed of the
two replaceable, stainless steel rods. The sampling vol­ume is an elliptical cylinder that extends approximately 3
cm out from the rods. The high frequency signal infor­mation is then converted to volumetric water content.
However, high amounts of clay and high electrical con­ductivity (EC>2 dS/m) will attenuate the high-frequency
signal and affect the reading displayed by the meter. Very
high organic matter content will similarly affect the VWC
reading.

When taking a measurement, it is important that the rods
be fully inserted into the soil. If not, part of the sampling
volume will be composed of air and the reading will be

6