Xylem H-4161 - Manual (Page 10)

2-2 Installation And Maintenance
H-4161
Note:
The SDI-12 logic and the 4-20mA interface are isolated from each other by digital optical isolators. The
SDI-12 logic is powered from the +12V input terminal, the 4-20mA circuitry is self-powered from the 4-
20mA loop. When the H-4161 is first powered up, the output current is set to 4.0mA. It remains at
4.0mA until the first successful data collection sequence. If the loop power is disconnected or is applied
after the SDI-12 side is powered up, the data in the digital-to-analog converter will be undefined. When
the loop power is restored, the 4-20mA output will be at an unknown value. Once a fresh SDI-12 data
collection is made the digital-to-analog converter will be loaded with new valid data.
2.4 Programming the H-4161
The H-4161 comes from the factory with the following settings:
H-4161 device address 0
Max setpoint: 20.00
Min setpoint: 4.00
Monitored Address: Z
Monitored Parameter: 1
AutoScan Command: 0 (0M!)
Module Mode: 0 (monitor)
Measurement Rate: 0 (seconds)
These setups are stored in Flash memory within the H-4161 and will not be lost if the power is removed.
The extended commands for changing these settings are described in detail in Chapter 3.
2.5 Programming the Sensor Address
The H-4161 comes from the factory with its sensor address set to “0". If more than one sensor is to be
connected to the SDI-12 bus, make certain each sensor has a unique sensor address, including any H-
4161 modules. The H-4161 is not a traditional sensor and does not ‘make measurements”. However, to
facilitate programming the H-4161 it must have a unique address.
2.6 Programming the Max and Min data setpoints
Captured SDI-12 data is scaled into 4-20mA units using the programmable Max and Min data setpoints.
This feature makes it easy to setup the H-4161 for your application. For example, if you are monitoring
stream stage which could be up to 10 feet, program the Max setpoint to 10.00. Perhaps the stream never
falls below 5 feet and you would like to narrow the dynamic range of the 4-20mA output for more
resolution. In this case program the Min setpoint to 5.00. A captured SDI-12 data value of 5.00 will
produce a 4.0 mA output and data value of 10.00 will produce 20.0mA. Note if the stage rises above
10.0 feet the output will clamp at 20mA or if the stage falls below 5 feet the output will clamp at 4.0mA.
The extended commands to examine or change the Min and Max values are explained in Chapter 3.