Xylem H-3553 - Manual (Page 17)

or meters is the stage units desired. This then requires the line pressure value to be changed to a different set
of units. Table 4-6 shows typical slopes required to convert pressure (PSI) units to other different stage units.
The H-3553 stage unit default is feet, which is a default slope of 2.0367. To change the stage units/slope using
the RS-232 main menu, press the ‘U’ key and then the up and down arrow keys to toggle to the desired units,
then press the ‘Enter’ key. If the desired stage unit is not listed change the stage units to user defined, press
the ‘L’ key and enter in the desired slope.
To change the H-3553 stage slope using the SDI-12 interface, send the “aXWSn.nn!” SDI-12 extended
command. The response should be “a0021” which means that it will take 2 seconds to complete the command
and then it will put 1 data value in the buffer. To check the slope and verify it was written correctly send “aXRS!”
and wait the responded time. Then send the “aD0!” command to read back the new slope.
Setup & Operation
15
SDI-12
The SDI-12 address of a sensor is its identifier on the SDI-12 data bus. The SDI-12 data bus is a one wire
communication between normally one master device and one or more slave devices. The SDI-12 address
makes it possible for the master device to communicate with each sensor individually. SDI-12 data collisions
will occur when two or more sensors have the same address on the same data bus. The sensors with the same
address will try to respond to the request of the master device at the same time and the result is garbage data.
Therefore, it is important to know the address of the sensor to which communication is desired and that there
are no other sensors with the same address.
H-3553 Combo Bubbler setup menu sDI-12 Interface
A - SDI-12 Address: a Command: aAn!
Enter New SDI-12 Address [n] Response: n
Table 4-5: Change the H-3553 SDI-12 Address The H-3553 SDI-12 address by default
is 0. To change the H-3553 SDI-12
address using the RS-232 main menu,
press the ‘A’ key and enter in the new “
SDI-12 address”.
To change the H-3553 SDI-12 address using the SDI-12 interface, send the “aAn!” command and the response
should be ‘n’, the new address. Note in Table 4-5, the ‘a’ is the current address of the H-3553 and the ‘n’ is the
desired new SDI-12 address.
Stage Units / Slope
The stage unit of a sensor is the setting that determines the
data output units. Different data units are dependent on the
slope/multiplier. The slope is multiplied by the raw data to
achieve the desired units. For example, a pressure sensor raw
data output might be in pressure (PSI) units, but the desired
units by the user is feet. Therefore, the slope to convert PSI to
Feet units for water depth is 2.0367 rounded.
The H-3553 has a pressure sensor that measures the pressure
required to push a bubble out of the orifice line, which is
the line pressure. The line pressure raw value is returned in
pressure (PSI) units. Normally, water depth in feet
units slopes (multiplier)
Feet 2.3067
Meters 0.7031
Inches 27.6800
Millimeters 0.0007031
Centimeters 0.007031
Feet Down -2.3067
PSI 1.0000
Table 4-6: H-3553 Stage Units and Slopes