Decagon Devices GS3 Manual - Halaman 11

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GS3 Integrator Guide
Note: Sometimes the signaling from the sensor can confuse typical microprocessor UARTs. The sensor
holds the data line low while it takes measurements. It raises the line high to signal the logger that it will
send a measurement as documented above. Then the sensor may take some additional measurements
before starting to clock out the first data byte starting with a typical start bit (low). Once the first start bit is
sent, typical serial timing is valid; however, the signal transitions before this point are not serial signaling
and may be misinterpreted by the UART.
DDI- SERIAL RESPONSE
The data string output by the sensor should be in a format similar to the one below:
<09>22.0
21.2
1302<0D>w8<0D><0A>
PARAMETER
DESCRIPTION
Tab character indicating the start of the TTL transmission.
<09>
Dielectric (ε
22.0
equation:
Note: Accuracy can be improved, especially in soilless media, with a medium-
specific calibration. See GS3 User Manual for details.
Temperature in °C
21.2
Electrical conductivity in µS/cm. Divide this number by 1000 to get mS/cm. This
1302
value is already temperature corrected within the GS3 sensor using the temperature
correction outlined by the US Salinity labs Handbook 60. Raw values for EC in tap
water can range from 100 to 800 µS/cm (0.100 to 0.800 mS/cm).
This carriage return character signals the end of the measurement string and start
<0D>
of the meta data string.
Everything below is this line is meta data:
Sensor Type. This character is used to indicate the sensor type. w is used for GS3
w
sensors.
Checksum. This one character checksum is used in our instruments to ensure that
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the data transmitted are valid. The checksum is used for sections listed above:
<09>22.0
See the following function for an example of how to implement the checksum
algorithm in C.
The carriage return and line feed are used to signal the end of the meta data
<0D><0A>
section and the end of the transmission.
. To convert to VWC for mineral soils, we recommend the calibration
a)
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X
10
*
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a
21.2
1302<0D>w
For support contact us via email at
or call us at 1.509.332.5600 between 7AM to 5PM PST
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X
10
*
. 3
67
X
a
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10
a
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