Xylem H-4161 - Manual (Page 6)

1-2 Introduction
H-4161
1.1 Description
The H-4161 includes a microprocessor, LCD display, 16-bit digital-to-analog converter, precision voltage
reference and a 4-20mA current transmitter. The SDI-12 and 4-20mA sections are isolated from each
other with a high voltage digital opto-coupler. Data collected from the SDI-12 bus is scaled by the
microprocessor into a 16-bit value and loaded into the digital-to-analog converter. The digital-to-analog
converter directly controls the current transmitter.
The H-4161 has two SDI-12 ports. The primary SDI-12 port provides data monitoring and
communication with the H-4161 device itself. When programmed to initiate measurements, the H-4161
makes measurements and collects the data from a sensor connected to the auxiliary SDI-12 port.
1.2 Display
The H-4161 has a 2-line x 16-character Liquid Crystal Display (LCD) which shows the current
measurement data. Line-1 displays the most recently captured SDI-12 data parameter. If the sensor
buffer is invalid (no data captured or the previous measurement failed) the message “no data” is shown
instead of a number. Line-2 displays the current setting of the 4-20mA output. Note: the mA value is the
desired loop current setting which the microprocessor loads into the digital to analog converter. If the 4-
20 mA loop is open, or insufficient loop voltage is present the actual loop current may be zero or may not
match the value on the display.
SDI = xxx.xx ft -
Iout = xx.xx mA
The character on the right hand side of Line-1 is an activity “spinner”. Every time a measurement is
captured or initiated, the spinner changes (rotates). This indicator shows measurements are being made
even if the measurement data is static (not changing).
1.3 Connectors
The H-4161 has a 5-position connector for making +12V and SDI-12 connections. The primary SDI-12
terminal is connected to the data logger and it’s attached sensors. If the H-4161 is to initiate
measurements, the auxSDI-12 terminal is connected to the SDI-12 sensor to be monitored. The 2-
position connector is for making connections to the 4-20mA loop.