Xylem H-4401 - Manual (Page 5)

H-4401
SDI-12 Bridge 1-3
Words of caution:
a. Even though the master H-4401 operates in a low power mode, the transmitter
requires 200mA for short bursts. Make certain your wiring and battery is capable of
supplying sufficient current.
b. Keep the lead wires as short as possible.
c. Use shielded cables in noisy environments.
d. Connect the ground post to a good earth ground.
e. Make certain each sensor has a unique SDI-12 address.
1.5 Troubleshooting
The radios can be difficult to field test when operating with a data logger due to the intermittent
short bursts of data. The radio system can be more throughly tested with the aid of a lap-top
computer or RS-232 terminal. With the following setup you can transmit ASCII messages or
other test data while adjusting or aligning the antennas. The radio link is tested by connecting a
computer terminal to one radio and connecting a loopback connector to the other. With this
setup, one person can test both up-link and down-link communication paths.
The radios have a standard RS-232C interface which operates at 9600 baud. With a straight-thru
9-pin RS-232 cable, connect the master radio to a laptop computer or terminal. The radios have a
female DB9 connector, pin-2 is received data output and pin-3 is transmit data input. The slave
radio must be setup for loopback operation. Do this by installing a loopback test connector or
connecting a jumper between pins 2 & 3. Make sure your computer is set for 9600 Baud.
The wireless link is best tested with a test program provided by the radio manufacturer. The test
program “X-CTU” can be downloaded from the www.maxstream.net website. X-CTU
automatically tests the wireless link and provides a success/fail display of each data packet.
Alternatively, you can use a terminal program such as XTALK, PROCOMM or HYPERTERM to
test the radio link. Make sure your computer or terminal is set for full-duplex operation. Test the
radio link by typing characters and checking for the proper echoed response. As you type, the
characters are transmitted to the remote station then re-transmitted back to the local station and
displayed on your screen. Both up-link and down-link paths are tested at the same time.