General information

SDI-12
SDI-12 is a standard for interfacing data recorders with microprocessor-based sensors. SDI-12 stands for serial/digital interface at 1200 baud. It can connect multiple sensors with a single data recorder on one cable. It supports up to 60 meter cable between a sensor and a data logger.

The standard process to carry out a measurement is to send a measurement request upon which the sensor responds with the time that is required to carry out the measurement and the number of data items being returned. After waiting the time that the sensor requires to carry out the measurement, the data recorder sends a “Read Command” to get the measurement results.

Example

Start Measurement Command 0M1!
Sensor 0 might respond 00012 which means the measurement will take 1 second and deliver 2 values.
After min. 30 seconds, the data recorder can send the “Read Data Command” 0D0! to which Sensor 0 might reply 0+67.75+17.23. +67.53+17.23 is the two measurement results which may be 67.75% soil moisture level and 17.23°C soil temperature.

Technical Specifications

Symbol Parameter Conditions Min Typ Max Unit
Is Supply current Active mode (during measurement)   8   mA
Is Supply current Sleep mode 80 µA
Vs Supply voltage 6 12 16 V
tm Measurement Time Time in active mode upon receiving a measurement command 1 s
Volumetric soil moisture measurement range 0 – 100 %
Volumetric soil moisture measurement accuracy Soil specific polynomial calibration ± 3 %
Soil temperature measurement accuracy Over complete operating temperature range ± 3 °C
Measurement frequency range nominal frequency set to 85 MHz 20 85 160 MHz
Temperature drift Tested in sand at 30% volumetric soil moisture value. +0.2 %/°C

Environmental Specifications

Symbol Parameter Conditions Min Max Unit
TA Operating Ambient Temperature Range   -20 +65 °C
TSTG Storage Temperature Range -40 +85 °C
Moisture level - 100 %

Calibration

As the maximum water storage capacity largely depends on the soil type, the sensors come factory calibrated.

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Technical Specs

Green Shield uses state of the art technology and combines it with scientific information to give you full control.

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How to use Green Shield

Learn how to install and remove your censors.

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