GroPoint 2625-N-T Series User manual

GroPoint™ Profile Multi Segment
Soil Moisture & Temperature
Profiling Probe
Models 2625-N-T-x, 2625-N-x, 2625-M-T-x, 2625-M-x
OPERATION MANUAL
March 2023
V1.1.3

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Table of Contents
Overview ........................................................................................................................... 4
Technology (TDT) .............................................................................................................. 4
GroPoint™ Profile Model Variations ...................................................................................... 5
Probe Technology .............................................................................................................. 6
Wiring Connections ............................................................................................................ 7
Reading Methods ............................................................................................................... 7
Sensor Start Up Time / Measurement Time .......................................................................... 7
Important Things to Note ................................................................................................ 7
Basic SDI-12 Command List ................................................................................................ 8
How it Works ................................................................................................................. 8
Basic SDI-12 Command List ............................................................................................. 8
Understanding the Basic Commands .................................................................................... 8
Query Address Command: ?! ........................................................................................... 8
Acknowledge Active Command: a!.................................................................................... 9
Send Identification String Command: aI! .......................................................................... 9
Change Address Command: aAb! ..................................................................................... 9
Start Measurement Command: aM! or aM1! or aM2! .........................................................10
Start Concurrent Measurement Command: aC! .................................................................10
Send Data Command: aD0! or aD! ..................................................................................10
Extended SDI-12 Command List .........................................................................................11
Overview ......................................................................................................................11
Extended SDI-12 Command List ......................................................................................12
Extended Command Descriptions .......................................................................................13
Sensor Board Power Control: aXSc! .................................................................................13
Read/Write Operating Mode Setting: aXMn! .....................................................................13
Read/Write Coefficient/Scale Factor Setting: aXCn! ...........................................................13
Additional Product Information ...........................................................................................18
Specifications ................................................................................................................18
Ratings .........................................................................................................................18
Appendix A: Probe Installation / Extraction ..........................................................................19
Summary ......................................................................................................................19
Sensor Installation Guidelines .........................................................................................20

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Slide Hammer and Pilot Rod Installation Method ...............................................................21
Auger Installation Method...............................................................................................22
Excavation Installation Method ........................................................................................22
Removing the Sensor from the Soil .................................................................................22
Appendix B: Soil Specific Calibration Process .......................................................................23
Introduction ..................................................................................................................23
Overview ......................................................................................................................23
Equipment Required.......................................................................................................24
Procedure .....................................................................................................................25
Entering Coefficients into the Probe .................................................................................29
Appendix C: Determining Volumetric Moisture Content (Weight Method – In Laboratory) ........31
Procedure Overview .......................................................................................................31
Equipment Required.......................................................................................................31
Soil Sampling Ring Requirements ....................................................................................31
Sampling Ring calculation ...............................................................................................31
Sampling Method ...........................................................................................................31
Example Calculation .......................................................................................................34
Appendix D: Modbus Programming Manual .........................................................................35
Modbus Command Functions ..........................................................................................35
Data Values ...................................................................................................................37
GPLP Modbus Register Lists ............................................................................................37
Detailed Description of Holding Registers ......................................................................40
Coil Registers ................................................................................................................42
Discrete Inputs ..............................................................................................................42
Appendix E: Accessories ....................................................................................................43
Certificate of Compliance EU/Declaration of Conformity ........................................................44
About GroPoint™
...................................................................................................................45

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Overview
The highly accurate GroPoint™ Lite Multi-Segment Soil Moisture and Temperature Profiling
Probe (GPLP) provides cost effective soil moisture measurement over several depths using a
single probe, eliminating the need for multiple sensors placed at different depths and cumber-
some installations. GPLP can be deployed in irrigation sensitive zones, to enable full control of
precision irrigation needs, providing an understanding of water movement through the soil. Pro-
filing moisture measurement is ideal in a multitude of agricultural applications including vine-
yards, row crops, and orchards as well as silviculture and research to better manage irrigation
practices, increase plant/crop quality and yield, and reduce fertilizer run-off.
The sleek light weight design installs quickly with minimal soil disruption using a pilot rod and
slide hammer tool. Designed for vertical installation, the sensor takes measurements over multi-
ple soil layers, with each measurement zone providing the average volumetric soil moisture con-
tent over a 15 cm (6 inch) zone. The probe is attached to a 3-meter (9.8’) cable. Soil tempera-
ture measurements are also available.
Technology (TDT)
GroPoint™ sensors and probes use Time Domain Transmissometry (TDT) and patented tech-
nology as the basis for its measurement. The patented technology employs a unique antenna
design that enables extremely accurate and repeatable measurements while maintaining a
highly cost-efficient electronics and mechanical design. TDT measures the time taken for an
electromagnetic wave to propagate (travel) along a given length of a transmission line in the
soil. Moisture in the soil changes the soil’s dielectric properties, so that the electromagnetic
wave travels at different rates in wet soil compared to dry soil. This allows for the accurate de-
termination of the soil moisture content.
GroPoint™ TDT⁵ profiling probes detect water as much as 5 centimetres (2 inches) from the
surface of the probe fins although, like all dielectric based sensors, moisture closest to the sur-
face of the probe has more influence on the readings than moisture further away, so that soil
closely surrounding the sensor will have a greater influence on the soil moisture reading than
the soil further away.

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GroPoint™ Profile Model Variations
The GroPoint™ Profile sensor can be ordered with and without temperature sensors. The in-
formation in this manual covers material for sensors with temperature sensors. If you have or-
dered sensors without temperature sensors, the commands applicable to the temperature sen-
sor readings will be inactive. Model numbers of sensors are as follows:
Cable Connection: Either flying lead or M12 Connector, Interface: SDI-12, modbus or RS485 + SDI-12
Length & Number of Segments Part No. With Temperature Part No. Without
Temperature
2 Segment (30 cm)
2625-N-T-2 2625-N-2
3 Segment (45 cm)
2625-N-T-3 2625-N-3
4 Segment (60 cm)
2625-N-T-4 2625-N-4
5 Segment (75 cm)
2625-N-T-5 2625-N-5
6 Segment (90 cm)
2625-N-T-6 2625-N-6
8 Segment ( 120 cm)
2625-N-T-8 2625-N-8
= temperature sensor placement
2
30 cm
3
45 cm
4
60 cm
5
75 cm
6
90 cm
8
120 cm
Segment 3 Segment 1 Segment 8 Segment 7 Segment 6 Segment 5 Segment 4 Segment 2

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Probe Technology
The drawing below shows the probe dimensions of the 2-8 segment probes, Temperature sen-
sor locations provided in table below:

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Wiring Connections
Wire Colour Function
Brown + Power (6.5V-18VDC)
White
MODBUS/RS485 D
-
Blue
MODBUS/RS485 D+
Black SDI-12 I/O
Gray Ground
*Standard cable wire colours. Other cable options available (may have different colours)
Optional M12 5-Pin Male A-Code Connector
Pin # Colour Function Pin Locations
1
Brown
+ Power (6.5V
-
18VDC)
2
White
MODBUS/RS485 D
-
3 Blue MODBUS/RS485 D+
4 Black SDI-12 I/O
5 Gray Ground
*Available as field installable option, with screw terminal wire
termination.
Reading Methods
The GPLP Lite multi-segment soil moisture profiling probes use the SDI-12 Protocol for serial
communications. The sensors conform to V1.3 of the SDI-12 protocol. Serial communication
settings are 1200 baud, 7 data bits, even parity, 1 stop bit. SDI-12 commands must begin with
a minimum 12.5 ms break signal, followed by an 8.3 ms mark space, then the command char-
acters. Note: for a complete description of the SDI-12 communications protocol, please refer to
http://www.sdi-12.org/specification.php
GroPoint™ Profile probes may be read with any compatible SDI-12, Modbus or RS485 logger,
communications interface, or reader unit. (RIOT offer accessories for reading SDI-12 sensors:
the GroPoint™ GP-DU SDI-12 Display Unit (Part# 2628) is a handheld display unit for
taking field readings; the GroPoint™ GP-USB Connect - SDI-12 Sensor (Part# 6300) is a
USB to Sensor interface that connects sensors directly to application software on a USB
equipped computer. GroPoint™ accessories are listed in appendix E of this manual.
Sensor Start Up Time / Measurement Time
Important Things to Note
The time from application of power to the SDI-12 power bus until the sensor is ready to receive
a command is approximately 350 ms. The reported measurement time in response to the M!
measure command (where “a” is sensor address) is 002 seconds. Actual measurement time is
approximately 100ms per segment, so the three-segment probe measurement will typically be
less than one second from the end of the aM! command response (a0021<CR><LF>) until the
measurement finished service request (a<CR><LF>). Power current consumption is at an

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active level (about 15-20 mA) only during measurement time, otherwise current is usually less
than 0.5 mA.
Basic SDI-12 Command List
How it Works
Following is a list of the supported commands for the sensor. In the descriptions below, SDI-12
command/response sequences are show in Courier font, with a box surrounding the text. The
command from the SDI-12 Logger/Recorder is shown in bold text. The response from the sen-
sor is shown in normal text. As is normal, SDI-12 commands are always terminated with the ‘!’
character. Responses from the sensor always include the sensor’s address as the first character
and are always terminated with the <CR><LF> (carriage return-line feed) sequence.
Basic SDI-12 Command List
The GroPoint™ Lite Profiling Probes respond to the following basic SDI-12 commands. In all
cases, a = sensor address. Default sensor address is ‘0’.
Command Meaning Response
?!
Address Query Device address (default address is ‘0’)
a
!
Acknowledge
Device address (default
address is ‘0’)
a
I! Send Identification Identification string
a
A
b
!
Change Address
Change device address to ‘b’
a
M!
aM1!, aM2!
Start Moisture Measurement
Start Temp. Measurement
Measure time and count (e.g. “a0023”)
a
C!
aC1!, aC2!
Start Concurrent Measurement Measure time and count (e.g. “a00023”)
a
D0!
aD1!*
Send Data Measurement values
* Necessary for GPLP-8 only, for segment 7 and 8 measurement values
All other commands received by the sensor will be acknowledged with the device address only.
Understanding the Basic Commands
Query Address Command: ?!
Use this command to query a sensor for its address. This will allow a user to determine the ad-
dress of a sensor if it is unknown. Please understand that if more than one sensor is connected
to the SDI-12 communication bus, they will all respond to this command, causing a bus conten-
tion, and usually a garbled response.

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For example, for a sensor with address ‘0’ (default address), the command/response sequence
is as follows:
?!0<CR><LF>
Acknowledge Active Command: a!
Use this command to ensure that a sensor is responding to a data recorder or other SDI-12 de-
vice. The command consists of the sensor’s address and the ‘!’ command termination character.
When this command is received by the sensor with matching address, it responds with its ad-
dress, followed by the <CR><LF> sequence.
For example, for a sensor with address ‘0’ (the default address), the command/response se-
quence is as follows:
0!0<CR><LF>
Send Identification String Command: aI!
Use this command to query the sensor for its SDI-12 compatibility level, vendor, model number,
and firmware version number. The command consists of the sensor’s address, the ‘I’ character,
and the ‘!’ command termination character.
For example, the response, for a sensor with address ‘0’ (the default address), is as follows:
0I!013RIOTTECHGPLPTN027SN300123<CR><LF>
This ID string identifies the supported SDI-12 compatibility level as 1.3, sensor vendor as
‘RIOTTECH’ (RIOT Technology Corp.), the sensor model as GPLPTN (GroPoint™ Lite Profiling
with soil temperature), the firmware version as ‘027’ (V2.7 firmware), and the sensor’s serial
number as 300123.
Change Address Command: aAb!
Use this command to change a sensor with address ‘a’ to new address ‘b’. The factory default
address for all sensors is the ‘0’ character. If there will be more than one sensor on the SDI-12
communication bus, they must all have a unique address. ASCII '0' through ASCII '9' are the
standard addresses. Should there be a need for more than 10 sensors, you can also use an ad-
dress in the range ASCII 'A' through ASCII 'Z' and ASCII 'a' through ASCII 'z'. The sensor re-
sponds with the new address, and the <CR><LF> sequence.
For example, the following command/response sequence changes a sensor with address ‘0’ to
address ‘5’:

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0A5!5<CR><LF>
Start Measurement Command: aM! or aM1! or aM2!
Use this command to start a sensor measurement. Use M! to start the soil moisture measure-
ments. Use M1! and M2! (6 or 8 segment probes only) to start the temperature measure-
ments. See specification sheet provided with sensor for more details. The sensor responds with
its address, and a string of numbers (e.g. ‘0024’) which represents the expected time in sec-
onds until the measurements will be ready (‘002’ seconds) and the number of measurements
that it will make (‘4’ measurements). The data recorder is then expected to wait (no other com-
mands may be sent) and monitor the SDI-12 communication bus up to the expected time, or
until the sensor responds with its address as a service request. The send data (D0!) command
can then be issued to get the measurements.
For example, sensors with address 0 and 1 respond as follows:
0M!00024<CR><LF> (sensor 0 will be ready in 002 seconds with 4 measurements)
0<CR><LF> (sensor 0 sends this when the measurement is complete)
1M!10024<CR><LF> (sensor 1 will be ready in 002 seconds with 4 measurements)
1<CR><LF> (sensor 1 sends this when the measurement is complete)
The actual measurement may take less than the expected time of 002 seconds. The service re-
quest will be sent by the sensors as soon as the measurement is complete, and data is ready.
Start Concurrent Measurement Command: aC!
Use this command to start a concurrent sensor measurement. The sensor responds with its ad-
dress, and ‘00204’ which represents the expected time in seconds until the measurements will
be ready (‘002’ seconds) and the number of measurements that it will make (‘04’ measure-
ments). The sensor begins the measurement process but does not send a service request on
completion. With a concurrent measurement command, the data recorder may send additional
commands to other devices while the sensor is busy taking measurements. Only after the ex-
pected measurement time has expired may the data recorder use the send data (aD0!) com-
mand to get the measurement data.
For example, sensors with address 0 and 1 respond as follows:
0C0!000204<CR><LF> (sensor 0 will be ready in 002 seconds with 04 measurements)
1C!100204<CR><LF> (sensor 1 will be ready in 002 seconds with 04 measurements)
Send Data Command: aD0! and aD1!
Use this command to instruct the sensor to return the measurement results. The sensor re-
sponds with its address, and the moisture values for each segment from top to bottom. Each
moisture value has the format ‘+mm.m’ which represents the volumetric moisture content in