QTech Data Systems DNP3 RTU - Manual (Page 4)

DATRAN XL4 DNP3 RTU – Quick Start Guide – v1 – May 2012
www.qtech.co.nz Tel: +64 3 3663713
Digital Outputs
The XL4 RTU Digital Outputs are designed to be easily interfaced with relays and
contactors.
The XL4 RTU has 8 Digital Outputs in total. Digital Outputs 1 to 4 are located on the front
panel adjacent to the Digital Inputs and have LED indicators to show if the output is active
or not. Digital Outputs 5 to 8 are located on the underside of
the RTU next to the power connector.
The Digital Outputs work as “Current Sinks”. This means
that when they are turned on, they will be connected to
power supply ground, allowing current to flow into the output
terminal to ground. In the “OFF” state, they have a high
impedance to ground and will float up to + Supply.
To use a digital output with a relay, wire as shown in the diagram opposite:
Analog Inputs
The XL4 RTU has 6 analog channels. All analog channels are independently capable of
operation as either 0-20mA, 4-20mA, 0-5V or 0-10V. In addition to this, channels 5 and 6
are independently able to be configured as either inputs or outputs. The XL4 RTU is
factory shipped with all analog channels configured as 4-20 mA inputs. For details on how
to reconfigure them, refer to the Owners Manual.
For all analog inputs, the current return path is via the ground of the XL4 RTU power
supply. It is important to understand the implications of this when wiring certain analog
devices to the RTU, as detailed below.
The LEDs adjacent to each Analog Input show the status of the signal the XL4 RTU is
receiving. If the LED is off, it means the input signal is zero, or under-range. When the
LED is on, it indicates the signal is within the measuring range that the input has been
configured for. If the LED is flashing, it shows the signal is over-range.
Loop Powered Devices
“Loop-Powered”, or “2-Wire” devices derive their power supply from the current flowing in
the loop itself. It is important to make sure that any device is rated to operate at the voltage
that will be available to it taking into account that the XL4 RTU Analog Input will drop 5V
across it at 20mA loop current.
For example: If the system is being powered from 13.7V
DC, the analog transducer will only have a maximum of
8.7V available to it for its power supply.
To wire a “2-Wire” device, refer to the diagram opposite:
Separately Supplied Devices
“Separately Supplied”, or “4-Wire” devices are analog
transmitters that have a separate power supply from the
analog signal loop. If suitable, these devices can be
powered from the XL4 RTU power supply. If the XL4
RTU power supply is not suitable, the analog sensor can be powered from a separate
power supply as long as the grounds of both the XL4 RTU and the other power supply are
connected together.
Wiring of a 4-Wire device is as shown: