Xylem H-4191 - Manual (Page 7)

H-4191
Operation 1-5
1.4 Testing the Interface
You can test the H-4191 with a simple RS-232 terminal or computer using a terminal program
such as Xtalk or Hyperterminal. The terminal program must assert either the CTS or DSR (or
both) input signals to the H-4191 to awaken it from sleep. The red LED on the H-4191 will be
illuminated when it is awake and ready to communicate. The interface is a full-duplex connection,
depending on the settings of your terminal program you may or may not be able to see what you
are typing on your screen. If you make a mistake while typing the command, use backspace key to
delete the previous keystroke. If you make a mistake and are not sure what is in the H-4191's
buffer, press the “!” or ENTER Keys to flush the buffer and start over.
When the H-4191 is first powered up it transmits a “H-4191 Initialized” debugging message to
the RS-232 port.
1.4.1 H-4191 Initiates the Commands
Try the following commands. The sensor address in these examples is “0" and the sensor is a
Design Analysis H-350 pressure sensor. If your sensor has a different address use the appropriate
address.
1. Check to see if you can communicate with the sensor.
Issue a “0I!” Identify command.
The sensor should respond with: “012 DAA H-350001S#000000V10”
2. Make a measurement.
Issue a “0M!” command.
The sensor should respond with: “00153”
After 14 seconds the sensor will send a service request: “0
Issue a “0D0" command to collect the data.
The sensor should respond with: “0+4.56+0.0000+0.2”
1.4.2 H-4191 Monitors the SDI-12 Bus
The H-4191 can be used to passively monitor the activity on a SDI-12 bus. You can observe both
the commands from the data recorder and the responses from the sensors. The communications
between a data recorder and a Model H-350 pressure sensor would appear as follows:
0M!00153
0D0!0+4.56+0.0000+50.0
In this example the data recorder issued a “0M!” command, the sensor responded with
“00153 “ (sensor 0, measurement time = 015 sec, 3 parameters will be returned).
Next, the data recorder issued a “0D0!” command and the sensor responded with
“0+4.56+0.0000+50.0 (sensor 0, stage = 4.56, PSI = 0.0, temperature = 50.0).