Endress+Hauser Fieldgate FXA520, Руководство по эксплуатации

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3 Function and System Design Fieldgate FXA520
14 Hauser
3.3 Signal channels
Fieldgate FXA520 has two HART input channels, two analog input channels, a RS-485 interface and
a relay output channel. More details are to be found in Chapter 3.5, System Architecture and
Chapter 4, Installation.
3.3.1 HART input channels
The two passive HART input channels use the digital signal provided by the HART devices only (no
A/D conversion). They can be used for:
• Point-to-point connection of two HART devices
• Connection of two HART multidrop segments via the FXN520 Multidrop module
3.3.2 Analog input channels
Two passive analog input channels allow the connection of an additionals two 4...20 mA devices.
3.3.3 RS-485 interface
The RS-485 interface can be used to connect to and communicate with auxiliary modules, e.g:
• HART multiplexer for connecting additional HART devices
• FXZ520 Input modules for connecting analog devices or switches
3.3.4 Relay output
The relay can be used to signal an alarm or save power:
• Alarm relay
The relay is configured as an alarm relay by not selecting the function "Power Down Devices
between Scan Cycles" on the device set-up page. It closes on power-up and opens on power-
down. The alarm circuit must be wired accordingly.
• Power save
For installations where power saving is at a premium, e.g. solar stations, the device power can
be wired via the relay. The function "Power Down Devices between Scan Cycles" is then
selected by ticking the checkbox, see Chapter 6.3.4. When the device scan is complete, the
relay is opened and the power to the devices is cut. When the next scan is due, the relay closes
and after a short delay to allow the device to power-up, the scan proceeds.