Xylem System 5000 Getting Started Guide - Manual (Page 22)

20
SYSTEM 5000™ HARDWARE
The 4-20mA output connection points are at
the far right of the lower terminal strip. Several
instrumentation applications use sensors that
provide an industry standard 4-20 milliamp output
signal. The System 5000
™
data logger / DCP
can output a 4-20mA signal based on any of its
inputs. For example, a user may want to connect
a temperature probe to the System 5000
™
and
convert the temperature value into a 4-20mA
output. A temperature probe on Analog Channel
1 that produces a 0 to 5 volt output representing
0 to 100 degrees Celsius could easily be setup to
produce a 4-20 mA output that represents the 0 to
100 degrees. The System 5000
™
does not actually
output a 4-20mA signal, but rather controls the
current in an isolated externally powered loop.
The following figure shows a basic connection
diagram.
4 to 20 Milliamp (4-20mA) Output
There are four analog input channels labeled Vin1 to Vin4. The standard input range for all channels
is 0 to 5 volts; however, because the Analog to Digital converter is highly accurate, it can accurately
measure low level ranges as well. Differential measurements can also be made on channels Vin1 and
Vin2 or on channels Vin3 and Vin4.
Analog Input Channels
There are two analog ground connection points. In order to preserve signal integrity, it is important
to use the analog grounds only for sensors connected to the analog section. The current flowing
through an analog sensor is relatively small and normally very stable. If a digital sensor has its ground
connection tied into the analog ground, the currents from the digital sensor will flow through the
analog circuitry causing voltage level shifts and noise based on digitalswitching. There should be
sufficient digital ground connection points for the digital sensors.Power grounds should not be
connected to analog grounds.
Analog Grounds
The +5Vref output is used for analog sensors requiring a precision reference voltage. The maximum
output current is 10 milliamps. The Analog to Digital converter uses this excitation for
its reference to provide a ratio-metric relationship for sensors using this excitation.
Switched +5.00 Volt Reference Excitation