Xylem H-4191 - Manual (Page 3)

Chapter 1
Operation
H-4191
Operation 1-1
1.0 Introduction
The W
ATER
LOG ® H-4191 is a RS-232 to SDI-12 gateway (interface) module. When connected
to a personal computer or RS-232 terminal the H-4191 can be used to test and monitor SDI-12
sensors and data recorders. The H-4191 allows a programable logic controller (PLC), remote
terminal unit (RTU) or other data collection device with a RS-232 interface to access SDI-12
sensors. The H-4191 provides the RS-232 to SDI-12 electrical interface, generates the critical
bus timing, parity and command retries needed for the SDI-12 bus protocol..
The “SDI-12 Serial-Digital Interface” is ideal for data logging applications with the following
requirements:
Battery powered operation with minimal current drain
Low system cost
Digital sensors output data directly in user units
Sensors are interoperable and available from many different manufacturers
The H-4191 has the following features:
Provides both electrical and protocol interface functions between RS-232 & SDI-12
Works with any sensor command/response message including vendor specific extended
commands.
Buffers the command so no special timing is required.
Generates proper parity for the SDI-12 bus.
Automatically sends SDI-12 retries.
Passes the sensor service request to the host.
Supports optional CTS/RTS hardware flow control for a slow host device.
Low power mode facilitates use with a RS-232 data radio.
LED shows when the H-4191 is awake.
Built in “sensor” can measure the battery voltage.
The H-4191 is packaged in a rugged plastic enclosure with screw mount ears. Connectors
located on each end provide easy hookup.