GroPoint Lite Manual

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GroPoint Lite!
TECHNICAL INFORMATION
The GroPoint Lite soil sensor is robust, reliable and highly
accurate, providing cost effective soil moisture and
temperature measurements. The sleek light weight design
installs quickly with minimal soil disruption. When installed
vertically, the sensor averages volumetric moisture
content over a soil layer of about 6” (15cm). When installed
horizontally, the sensor can be used to measure moisture
at a specific soil depth.
Wiring Legend!
0-5mA and 4-20mA
Note that the analog GroPoint Lite also includes a green cable, but it should not be
connected in an installation. It is used only for calibration and testing.
⚫︎ Red: DC input voltage
⚪︎ White: Analog output
⚫︎ Black: Ground/Common
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GroPoint™ is a division of RioT Technology Corp.
1 833 GRO-POIN (N. America) or 250 412 6642
gropoint.com

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SDI-12
RS-485!
Rugged Connector!
Environmental sealing:
•Integral O-Ring gasket
•IP68 seal rating
Materials:
•Connector shell: thermoplastic
•Shell interior: Elastomeric
•Contacts: Copper alloy
•Contact plating: Gold over nickel
Mounting procedure:
Align connector, push on, rotate bayonet ring until tight.
⚫︎ Red: DC input voltage
⚪︎ White: SDI-12 I/O
⚫︎ Green: Ground/Common
⚫︎ Black: no connection
⚫︎ Red: DC input voltage
⚫︎ Black: RS-485 I/O A
⚪︎ White: RS-485 I/O B
⚫︎ Green: Ground/Common
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GroPoint™ is a division of RioT Technology Corp.
1 833 GRO-POIN (N. America) or 250 412 6642
gropoint.com

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Connector Pinout!
SDI-12 Command Set !
The GroPoint Lite (SDI-12 and RS-485 version) conforms to/implements all aspects of the
SDI-12 V1.3 protocol specification (a = sensor address).
All other commands received by the sensor will be acknowledged with the device
address only.
Analog
Digital
!
Command
Meaning
Response
a!
Acknowledge
Device address (default address is '0')
aI!
Send identification
Identification string
aAb!
Change address
Change device address to ‘b’
?!
Address query
Device address
aM!
Start moisture measurement
Measurement time and count (e.g. “a0026”)
aM1!
Start temperature measurement
Measurement time and count (e.g. “a0023”)
aC!
Start concurrent measurement
Measurement time and count (e.g. “a00206”)
aD0!
Send data
Measurement results
aD1!
Send data
Additional data (if necessary)
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GroPoint™ is a division of RioT Technology Corp.
1 833 GRO-POIN (N. America) or 250 412 6642
gropoint.com

™
Sensor Start-up Time / Measurement Time!
The time from application of power to the SDI-12 power bus until the sensor is ready to
receive a command is approximately 75ms. The reported measurement time in response
to the aM! measure command (where a is sensor address) is 3 seconds, measured from
the end of aM! command response (a0022<CR><LF>) where n is the number of
segments. Actual measurement times are less, and a service request is issued as soon as
the measurement is completed. Current is at active level (15-20 mA) only during
measurement time, otherwise current is less than 0.1 mA.
Testing the GroPoint Lite (4-20mA)!
If desired, you can test the GroPoint Lite sensor before deploying it. The following test is
for functional testing only, NOT determining calibration values. It is only to confirm that
the sensor output increases with moisture increases, as it lacks the precision and
controlled environment used for calibration.
Materials Required!
To perform this test, you will need the
following:
•A 12V power supply.
•A digital multimeter set to 0-30mA.
•A 100 ohm to 500 ohm sense resistor.
•A plastic or glass container (NOT metal) at
least 15cm (6”) in diameter. It should be deep
enough to completely cover the sensor with
water when the sensor is held vertically
(about 23 cm, or 9” deep), although
acceptable results will still be obtained if
sensor is covered with water when
positioned diagonally in the container (about 17 cm, or 7” deep). The readings you
obtain may differ from stated if you use a different container.
•Water to fill the container.
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GroPoint™ is a division of RioT Technology Corp.
1 833 GRO-POIN (N. America) or 250 412 6642
gropoint.com

™
Connection Diagram!
Testing Instructions!
1. Take a reading on the multimeter before submerging the sensor in water. The initial
reading (in air) should be approx. 0.15 mA.
2. Slowly dip the sensor into the water, tip of
the sensor first. After the first 3 cm of the
sensor being submerged, the current
readings will start to increase.
3. When about half the sensor is submerged,
take another reading. The current should be
measuring around 14 to 15 mA.
4. Take a final reading when the sensor is fully
submerged. At this point, the current should
read about 22 mA.
If you obtain readings that are significantly
different than these, contact us.
Note: the probe is calibrated for operation in
soil, not water columns, so any values
obtained are approximate. Absolute value is not important, what is important is a
gradual, consistent increase as the probe is lowered into the water.
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GroPoint™ is a division of RioT Technology Corp.
1 833 GRO-POIN (N. America) or 250 412 6642
gropoint.com
The sensing element does not start
until about 3 cm from the tip of
sensor (see image below), so
readings won’t change immediately,
but will start to increase as the
sensor is lowered deeper into the
water, and steadily increase until it is
fully immersed in water.