SOMMER SPA-2, Руководство пользователя

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11.3.9 Sommer CRC-16
The CRC-16 (cyclic redundancy check) used in data transmission of Sommer devices is based on the
ZMODEM protocol. When data are exchanged between two devices the receiving device calculates
the CRC-value. This value is compared to the CRC value sent by the other device to check if the data
were transmitted correctly. Please refer to technical literature or contact Sommer for calculation of
CRC-16 values.
11.4 SDI-12
11.4.1 What is it?
SDI-12 (Serial Data Interface at 1200 Baud) is a serial data communication standard for interfacing
multiple sensors with a single data recorder. For a detailed description on SDI-12 communication
please refer to
www.sdi-12.org .
11.4.2 What can I do with it?
The SPA-2 listens to standard SDI-12 commands as listed in the SDI-12 specifications of version 1.3,
e.g., to trigger a measurement or retrieve measurement results. Additionally, a set of extended SDI-
12 commands is implemented in all SOMMER sensors for instrument configuration.
11.4.3 How do I wire it?
The SPA-2 can be connected to a data logger via SDI-12 according to the figure below.
SDI-12 uses a shared bus with a ground wire, a data wire (indicated as SDI-12) and an op12 V
wire.
NOTE The connection with the 12 V power supply is optional and depends
on the connected SDI-12 master device (typically a data logger).
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