Apogee Instruments S2-431 Manual del usuario - Página 11
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OPERATION AND MEASUREMENT
The S2-431 Red - Far-red sensor has a SDI-12 output, where red and far-red photon flux density is returned in
digital format. Measurement of S2-431 Red - Far-red sensors requires a measurement device with SDI-12
functionality that includes the M or C command.
Wiring
Sensor Calibration
All Apogee SDI-12 S2 sensor models have sensor-specific calibration coefficients determined during the custom
calibration process. Coefficients are programmed into sensor microcontrollers at the factory.
SDI-12 Interface
The following is a brief explanation of the serial digital interface SDI-12 protocol instructions used in Apogee S2-
431 Red - Far-red sensors. For questions on the implementation of this protocol, please refer to the official version
of the SDI-12 protocol:
http://www.sdi-12.org/specification.php
Overview
During normal communication, the data recorder sends a packet of data to the sensor that consists of an address
and a command. Then, the sensor sends a response. In the following descriptions, SDI-12 commands and
responses are enclosed in quotes. The SDI-12 address and the command/response terminators are defined as
follows:
Sensors come from the factory with the address of "0" for use in single sensor systems. Addresses "1 to 9" and
"A to Z", or "a to z", can be used for additional sensors connected to the same SDI-12 bus.
"!" is the last character of a command instruction. In order to be compliant with SDI-12 protocol, all commands
must be terminated with a "!". SDI-12 language supports a variety of commands. Supported commands for the
Apogee Instruments SQ-400 series two-band radiometers are listed in the following table ("a" is the sensor
address. The following ASCII Characters are valid addresses: "0-9" or "A-Z"). Please note that SDI-12 commands are
case-sensitive.
White: Positive (signal from sensor)
Red: Input Power
Black: Ground (from sensor signal and output power)
Clear: Shield/Ground
(version 1.4, August 10, 2016).