Spectrum Technologies Fieldscout TDR 350 User manual

TDR 350
Soil Moisture Meter
PRODUCT MANUAL
Item # 6435

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Thank you for purchasing the Field ScoutTM TDR 350
soil moisture meter. This manual describes the meter's
general features and operation.
Soil moisture is a critical, and potentially highly varia-
ble, component of the soil environment. Time domain
reflectometry is a proven technology for quickly and
accurately determining volumetric water content
(VWC) in soil. Electrical conductivity (EC) is a func-
tion of the moisture and salt in the soil and can be fac-
tored out to increase the accuracy of VWC measure-
ments. The meter also measures soil surface tempera-
ture. The user can quickly transition between taking
VWC readings in standard, high-clay, and sand soils.
The TDR 350’s shaft-mounted probe allows the user to
take measurements while standing. The meter’s built-in
data logger eliminates the need to record data manually.
The data points can be viewed with the FieldScout Mo-
bile app that maps out soil measurements using logged
location coordinates. Measurements can also be saved
to an external USB flash drive when plugged into the
built-in USB port.
Contents
Includes the following components:
- TDR 350 meter (in collapsed position)
- Carrying case
- 4 AA batteries already installed
Note: TDR rods are sold separately
General overview

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CONTENTS
General Overview 2
Specifications 4
Product Dimensions 5
Button Functions 6
Display Screens 9
Meter Operation 10
Meter Care 11
Maintenance: Display and Battery Removal 12
Maintenance: Display and Sensor Replacement 13
Data Logs 14
Field Scout Mobile App/SpecConnect 16
Pairing TDR350 with FieldScout Mobile App 18
VWC Measurements 20
Electrical Conductivity 21
Optional Accessories 22
Appendix 1: Soil Specific Reading Correlation 23
Appendix 2: Troubleshooting 24
Appendix 3: Updating Device Firmware 25
Appendix 4: Calibration 26
Warranty Info 28
Declaration of Conformity 28
This manual will familiarize you with the features and operation of
your new Field ScoutTM TDR 350 Soil Moisture Meter. Please read
this manual thoroughly before use

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Measurement
Units
Percent volumetric water content (VWC)
Period (raw sensor reading)
Resolution,
Accuracy and
Range
VWC: 0.1% increment ±3.0% @ < 2 mS/cm
0% to Saturation (Saturation is typically around
50% volumetric water)
EC: 0.01 increment ; ± 0.1 mS/cm; 0 - 5 range
Temperature: 0.2 ˚F (0.1 ˚C) increment ; ± 1.8
˚F (± 1 ˚C); -22 to 140 ˚F (-30 to 60 ˚C)
Thermistor based; Infrared Optional
Connectivity USB Type A, Bluetooth Low Energy
(GNSS)
Accuracy 1m (Galileo), 3.5 to 10m (Glonass,
GPS)
WAAS and EGNOS enabled
Power 4 AA alkaline batteries
Log Capacity 50,000 measurements
Display Backlit, high-contrast, graphic LCD
Weight 4.3 lbs. (1.9 kg)
IP Rating Display: IP54, Probe: IP67
Probe Head
Dimensions
2.4” x 1.4”
(6cm x 3.5cm)
Shaft
Dimensions
Extended Length: 38” (96.5cm)
Collapsed Length: 23” (58.4cm)
Width: 1.4” (3.5cm)
Available
Rod
Dimensions
Turf 1.5” (3.8cm)
Short 3.0” (7.6cm)
Medium 4.8” (12.2cm)
Long 8.0” (20.32cm)
Diameter: 0.2” (0.5cm)
Spacing: 1.2” (3cm)
Specifications

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Product dimensions
The following are the dimensions of a fully extended TDR
350. It is possible to reduce the length of the meter to
23” (58.5 cm) by adjusting the lower half of the shaft.

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Button Functions
ON/OFF or BACK button
− Press briefly to power on.
− Press and hold to stay on logo screen.
− Press for 2 seconds to power off.
− Press briefly within a menu to return to prior
screen.
MENU or SELECT button
− Press to enter available menus.
− Press to select or confirm a menu selection.
DELETE or UP button
− Press to move up within a menu.
− Delete last measurement from the running aver-
age, counter, and its entry from the internal data
log (see p. 14).
READ or DOWN button
− Press to move down within a menu.
− From Reading screen, press briefly to make a
reading.
− Press and hold to clear the average and reset the
sample count to 0.

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Display Screens
The TDR 350 has 3 main display screens;
- Startup Information (shown on previous page)
- Reading (figure 1)
- Settings Menu (see p. 8)
Startup Information screen
Initially displayed after first powered on.
- Displays firmware version information.
- Press and hold ON/OFF|BACK button to remain on this screen.
Reading screen
Measurements from the sensor are displayed on the Reading
screen along with rod size used, soil type, and a reading count
with running average.
Press READ to take readings, update Count and the Average.
Indicators:
Battery level icon: upper right corner.
Bluetooth icon: displayed when enabled. A bar appears
through it when not actively communicating.
GNSS location icon: When enabled,
Transitions from clear to dark as location
fix is achieved. Crosshatch appears when WAAS/EGNOS in use.
Figure 1.Sample Reading screen

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Settings Menu screen
Used for changing device features, setting rod length and working
with log files.
Use arrow buttons to move to the desired option.
The Select button toggles through option choices.
Clear Average*:
Clear the current average and resets the counter.
Rod Length: Select the Rod length See page 4 for options.
Soil Type: Standard, Hi-Clay or Sand.
- Standard: for most mineral soils.
- Hi-Clay: for soils with higher clay content (> 27%).
- Sand: for sand based fields or turf greens.
Clear Logs*: Erases data logs from internal memory.
Save to USB*: Transfers data logs to a USB flash drive if at-
tached.
Backlight: Sets the LCD backlight: ON, OFF, AUTO. In AUTO
mode, the backlight will shut off 5 seconds after a button press
GNSS Location: Enable or disable geo-location fix for new log
entries
Bluetooth: Enable or disable Bluetooth connectivity to the Field-
Scout™ Mobile app (See p. 16).
Sound: Enable or disable beep for audible feedback.
Temp Source: Changes displayed temperature from the Soil Sen-
sor to the IR Sensor (optional).
Temp Units: Fahrenheit or Celsius scale.

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Moisture Type: Volumetric water content (VWC%), raw sensor
reading (Period), or TDR 300 mode.
- VWC%: displays the volumetric water content with temperature
and EC compensation.
- Period: displays the raw sensor reading - for troubleshooting or
soil-specific calibration.
- TDR 300: displays VWC output without temperature or EC
compensation
EC Units: EC value (mS/cm) or Salinity Index (see p. 21).
Auto-Off: Power off delay: 15, 30, 45, 60 minutes.
Current Date, Current Time: Reported values are acquired
from the satellite location signal.
Timezone: Offset from Greenwich Mean Time. As the offset
changes, the Time and Date will update.
Daylight Savings: ON or OFF.
Calibration*: Overrides factory calibration. See Appendix
Factory Defaults*: Resets menu settings and counter to the fac-
tory default value.
* Pressing Select button for these options brings up an additional
screen.
Rod Length None
Soil Type Standard
Backlight,
GNSS,
Bluetooth
Disabled
Sound On
Temperature Fahrenheit
Temp Source Soil Sensor
Moisture VWC
EC units mS/cm
Auto-Off 15 minutes
Time Zone GMT

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Meter Operation
Setting up the meter
1. Adjust the length of the collapsible shaft (fig. 1) by removing
the fastening bolt and either extending or retracting the shaft to its
new position, re-insert the fastening bolt, and hand tighten.
2. Screw in and tighten the rods into the sockets at the bottom of
the probe block.
3. Set the desired user settings in the settings menu. See the Set-
tings Menu (p.8).
Taking Readings
1. Grip the TDR handles to the left and right of the display.
2. Push down on the handles maintaining a steady downward
pressure to drive the rods into the soil until the sensor base is in
contact with the soil surface. Be sure not to allow back and forth
or side to side movement. This can introduce air pockets into the
soil medium which will alter the reading.
Caution: Exercise care not to damage the rods. See Meter Care
(p. 11).
3. Press the READ button and observe the change in results on
the top display.
Figure 1. Shaft, fastening bolt, and rods

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The FieldScout TDR meter will function properly under normal
conditions experienced in field use. The sensor block is sealed
and will not be damaged by immersion in water. The display is
not waterproof, so it should not be used during heavy rainfall or
left exposed during irrigation events. If the display does get wet, it
should be dried out immediately.
Follow these tips to prolong the life of the device:
- Store in a cool and dry place when not in use.
- Keep the meter and probe rods clean and dry in between uses.
- Remove the batteries if not used for an extended period of time
(ie: between seasons).
Battery life
If the battery level is low or a
battery is inserted incorrectly,
the low battery icon appears on
the screen and the display will
power off.
Battery life is affected by the
enabled features, accessories
connected, and the frequency of use. If not needed, the Bluetooth,
GNSS Location and backlight features can be disabled. The back-
light can also be set to AUTO mode (p. 8). This allows enough
time to see the reading and conserve the battery. The chart below
gives a rough estimate of the number of readings that can be taken
given certain configuration parameters.
Meter Care
Total Readings
Bluetooth GPS Backlight Alkaline Lithium
ON ON ON 12,000 24,000
ON ON OFF 24,000 35,000
OFF OFF OFF 150,000 225,000

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Maintenance
Display and Sensor Removal:
1. Remove the rods.
2. Flip the TDR display over.
3. Remove the 4 screws at each corner.
4. Gently separate the display module from the base plate. Note:
The sensor cable is attached in the center and should be
pulled slightly out of the base plate for battery, sensor, or
display replacements. Procedures are shown in the following
sections.
Battery Replacement:
1. Follow steps above for Display and Sensor Removal to
access the batteries.
2. Install four AA batteries and ensure correct polarity by
referencing the (+) positive and (-) negative labels at either
end of each slot.
3. Follow the procedure on the next page to reinstall the display.
plug
cable
Figure 1. Sensor cable con-
nection to board. Figure 2. Shaft interface

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Display Removal:
1. Follow steps for Display and Sensor Removal to access the
display and cable connections.
2. Remove the foam spacer and unplug the sensor cable connect-
or from the jack. If an IR temperature sensor is connected,
disconnect this plug as well. Do not discard the foam spac-
er.
Display Installation:
1. Follow the procedures for Display Removal to access the dis-
play and cable connections.
2. Re-connect the sensor cable to the 3.5mm connector on the
back of the display module.
3. Insert the foam spacer back into place behind the sensor cable.
The forked end fits around the sensor cable molding.
4. If equipped with the IR temperature sensor option, attach it to
the smaller diameter connector.
5. Guide the excess cable length back down through the base
plate.
6. Mount the display back onto the base plate by tightening the
four screws. Be sure the USB port side faces the same side as
the serial number label.
Sensor Block Removal / Replacement:
1. Follow steps for Display Removal to access the cable con-
nections.
2. Remove the fastening bolt that joins the probe block to the
shaft.
3. Separate the probe block from the shaft (fig. 2).
4. Feed the cable from the replacement probe block through the
shaft. A string fed down from the top can be used to aide in
the process of cable reconnection.
5. Follow the procedure for Display Installation to complete the
replacement.

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Downloading Data
Data stored in the meter's internal memory can be transferred to your PC
with a USB flash drive.
1. Connect the flash drive to the meter’s USB port.
2. Press the Menu/Select button on the bottom left of the display to
open the Settings Menu.
3. Choose the Save to USB option.
4. When prompted, press the Menu/Select button.
The data will be saved to the flash drive as a .csv file named with the
serial number as the filename. If a previous data file exists on the flash
drive with the same filename, it will be over-written*.
*Caution: If you cleared the data log before taking the current set of
measurements, be sure any data on the flash drive has already been
saved to your PC.
Erasing Data
Press the Menu/Select button (p. 6) to open the Settings Menu. Scroll to
the Clear Logs option and, again, press the Menu/Select button. Press
Menu/Select button to complete the process or the On/Off/Back button
to abort.
Figure 1: Sample TDR 350 data file
Data Logs

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Managing Data
The data is stored in comma-delimited text files. The file name will
match the serial number of your meter. These files can be opened with
text-editing software or spreadsheet software (fig. 1). The data is separat-
ed into 15 fields.
a Time is based on the GMT offset selected in the Timezone option (p. 9)
b If "TDR 300" is selected as the Moisture Type, the TDR 300 VWC
(without EC optimization) will appear in the VWC% column
c GNSS format is -DD.DDDDDD
Where DD.DDDDDD are decimal degrees, and a negative sign may ap-
pear for South or West compass directions
d Satellite fix status will be: 0 if unable to determine a location, 1 for lo-
cation without differential correction, and 2 for location with differential
correction
e Rod length options are L: Long (8"), M: Med (4.8"), S: Short (3"), and
T: Turf (1.5")
f Soil Type options are S: Standard, H: Hi-Clay, and D: sanD.
g Indicates whether the value in column B is EC-compensated (V) or not
(3)
Column Description
1Date and timea
2 - 8 Sensor readingsb
(VWC, Period, EC, Soil Temperature, IR Temperature)
9 - 10 Location fix coordinates (longitude, latitude)c
11 Number of satellites visible during reading
12 Satellite fix statusd
13 Rod lengthe
14 Soil typef
15 VWC Modeg

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The FieldScout Mobile App can be used to send data directly to
the SpecConnect web interface. Data can be viewed on a
Smartphone in two formats. In grid mode, the site is divided into
a customizable 2-dimensional grid of 3 to 5 rows and 3 to 5 col-
umns. Measurements are taken in each grid cell. Average, color-
coded data are displayed on the app (Fig. 1). In freeform mode, a
color-coded pushpin icon is placed at every sampling point. If the
TDR has a good GNSS location fix (p. 7), the app will use the
coordinates from the meter. If not, or if the meter's GNSS location
is disabled, it will use the internal location of the smartphone.
The data from the Pro version of the app is sent instantaneously to
SpecConnect. Data can be viewed in map form (fig. 3), exported
to a spreadsheet, or viewed as a Trend Report (fig. 4).
More details are available in the user's guide for the app.
Field Scout
Mobile App/
SpecConnect
Figure 1. Grid Mode Figure 2. Freeform Mode

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Fig. 3. 2-D Contour Plot in SpecConnect
Fig. 4. Trend Report

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The internal Bluetooth radio must be paired with the smartphone
running FieldScout Mobile. For some smartphone operating sys-
tems, it may be necessary to manually enable Location Services.
1. Activate Bluetooth feature on the smartphone.
2. Open the app.
3. Tap the Course/Farm icon. Select an ex-
isting course or create, name, and select
a new course.
4. Select an existing session or create,
name, and select a new session. This will
bring up the Select Session Mode screen
(Fig. 1). Select whether you are using
Grid or Freeform (Pro version only)
mode to collect data.
5. a. For Grid mode, the Main Grid screen (Fig. 2a) will appear.
Confirm that the meter you are using appears at the top of the
screen. If not, a new session must be created. Tap any of the
zones to bring up the Take Reading screen (Fig. 2b).
Figure 1. Session
Mode screen
Figure 2a. Main
screen
Figure 3. Bluetooth
Connect button
(freeform)
Pairing With The
FieldScout Mobile App
Figure 2b. Bluetooth
Connect button (grid)

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b. For Freeform mode, the app will immediately transition to the
Take Reading screen (Fig. 3).
6. Tap the Connect FieldScout Device via Bluetooth button. If
the Bluetooth feature has not been activated, you will be
prompted to do so.
7. The app will search for the Bluetooth device. It should then ap-
pear in the list of scanned devices (Fig. 4).
After selecting the device, the App will be ready to take readings.
Note: Although the device appears in the app, it may not appear on
the phone's list of Bluetooth devices.
Figure 4. Scanned device list

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VWC Measurements
Volumetric Water Content (VWC)
The ratio of the volume of water in a given volume of soil to the total soil
volume expressed as a decimal or a percentage. Three soil moisture
levels of most importance can be defined as follows:
Saturation: All soil pores are filled with water. The VWC will equal the
percent pore space of the soil.
Field Capacity: The condition that exists after a saturated soil is allowed
to drain to a point where the pull of gravity is no longer able to remove
any additional water.
Permanent Wilting Point: The highest moisture content at which a plant
can no longer extract water from the soil.
Additionally, we can define Plant Available Water as the amount of
water between Permanent Wilting Point and Field Capacity. One rule of
thumb is that irrigation should be initiated when half the Plant Available
Water has been depleted.
Time Domain Reflectometry (TDR)
The speed of an electromagnetic wave along a waveguide in soil is de-
pendent on the bulk dielectric permittivity () of the soil matrix. The fact
that water ( = 80) has a much greater dielectric constant than air ( = 1)
or soil solids ( = 3-7) is exploited to determine the VWC of the soil. The
VWC measured by TDR is an average over the length of the waveguide.
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. High amounts of clay or high
electrical conductivity (EC>2 mS/cm) 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.