User's Guide

1. Introduction
1.1. Product Overview
The Remote Terminal Unit (RTU) model M717 is a low power GSM/GPRS/UMTS/LTE based communication
device, that includes flexible bus/serial interfaces and a data-logging unit. The M717 RTU supports
following protocols and Input/Output (I/O) interfaces (see figure below):
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SDI, can be switched under software control between SDI-12 native, RS-485 or CAN;
•
MPI, or Multi Protocol Interface; can be switched under software control between RS-232, RS-422
and RS-485;
•
USB micro AB.
The M717 RTU can operate with multiple data sources, even simultaneous on both interfaces (e.g., several
SDI-12 sensors on SDI and a Thies DL16 data logger on MPI). The M717 RTU supports a maximum of 50
sensors with a total of max. 128 sampled values (tags) per data record. The SDI-12 implementation also
supports output tags by using specially designed, custom “X” commands (e.g., for switching valves). The
Davis and Thies implementations support one sensor (the data logger) with a total of max. 128 sampled
values (tags) per data record. The internal data logging memory (FIFO—First In, First Out) can store up to
half a million individual values, the older values being overwritten when the memory fills up.
The SDI-12 implementation conforms to the SDI-12 specification version 1.3. For additional information
on the SDI-12 bus, please consult the following document: “SDI-12, A Serial-Digital Interface Standard for
Microprocessor-Based Sensors, Version 1.3”. The document can be found on the SDI-12 Support Group’s
web site at http://www.sdi-12.org.
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