Apogee SI-421 Manuale d'uso - Pagina 12

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Apogee SI-421 Manuale d'uso
SDI-12 Interface:
The following is a brief explanation of the serial digital interface SDI-12 protocol instructions used in
Apogee SI-400 series infrared radiometers. For questions on the implementation of this protocol, please
refer to the official version of the SDI-12 protocol:
January 26, 2013).
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 SI-400 series infrared radiometers are listed in the following table
("a" is the sensor address. The following ASCII Characters are valid addresses: "0-9" or "A-Z").
Supported Commands for Apogee Instruments SI-400 Series Infrared Radiometers
Instruction Name
Send Identification Command
Measurement Command
Measurement Command w/ Check
Character
Change Address Command
Concurrent Measurement
Command
Concurrent Measurement
Command w/ Check Character
Address Query Command
Get Data Command
Make Measurement Command: M!
The make measurement command signals a measurement sequence to be performed. Data values
generated in response to this command are stored in the sensor's buffer for subsequent collection using
"D" commands. Data will be retained in sensor storage until another "M", "C", or "V" command is
http://www.sdi-12.org/specification.php
Instruction Syntax
aI!
aM!
aMC!
aAn!
aC!
aCC!
?!
aD0!
(version 1.3,
Description
Send Identification Information
Tells the Sensor to take a
Measurement
Tells the Sensor to take a
Measurement and return it with a
Check
Character
Changes the Address of the Sensor
from a to n
Used to take a measurement when
more than one sensor is used on the
same data line
Used to take a measurement when
more than one sensor is used on the
same data line. Data is returned
with a check character.
Used when the address is unknown
to have the sensor identify its
address
Retrieves the data from a sensor
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