Xylem H-339 - Manual (Page 10)

H-339
Operation 1-5
Operation
The H-339 includes an integrated GPS module capable of tracking up to12 satellites at a time. The
SDI-12 section of the H-339 handles power management and all communication between the data
recorder and the GPS module. During normal operation, the data recorder sends an address together
with a command to the H-339 sensor. The H-339 wakes up from its low power sleep mode, turns
on and collects data from the GPS module and stores the data in its data buffer. Once the data is
ready, the data recorder collects the data from the H-339's data buffer.
Programming the H-339
The H-339 comes from the factory with its address set to ‘0'. This is the only option that can be
programmed on the H-339. Use the change address command explained in chapter 2 to change the
address. The address is stored in EEPROM within the H-339 and will not be lost if the power is
disconnected. If more than one sensor is to be connected to the SDI-12 bus, make certain each
sensor has a unique sensor address.
The H-339 will also ALWAYS respond to valid commands with an address of ‘g’. The H-339 was
mainly developed for use with the W
ATER LOG Series of data logger providing a means to keep the ®
time clocks as accurate as possible. The data logger will always use ‘g’ as the address for
communicating with the H-339.
Programming the Data Recorder
Even though the H-339 was mainly developed for use with the W ATER LOG series of data logger, ®
it may be used with any data logger that has an SDI-12 interface. The following describes both
applications.
Generic Data Logger: You must prepare your data recorder to receive and record the H-339 data.
Since data recorders differ widely, refer to your recorder manufacturer's directions. In general,
program the data recorder to measure and record up to 9 values from the H-339 sensor via the
SDI-12 port. Your data recorder must issue an “aM!” command then collect the data with a “aD0"
and “aD1" commands, as explained in Chapter 2.