Field Xpert
3 Function and System Design
Hauser
9
3.2
Connecting to HART devices
Caution!
• Proof of intrinsic safety must be checked when additional devices are introduced into a loop.
3.2.1
VIATOR Bluetooth modem
The VIATOR Bluetooth modem allows point-to-point connections to be made with a HART device.
There are two possibilities of making it:
• For a normal transmitter power supply, e.g. RMA42, via a 270
load resistor (250
– 1100
) connected into the loop as shown in Fig. 3-2
• With a transmitter power supply with built-in HART communication resistor, via the two
HART communication sockets on the front panel as shown in Fig. 3-3. Suitable HART
transmitter power supplies are:
–
RNS221, RMA422, for non-Ex applications
–
RN221, RMA421 for Ex and non-Ex applications
The connection between the Field Xpert and the modem is wireless (Bluetooth).
Notice!
• The modem is certified for use in hazardous areas, Zone 1. Once a modem has been used in a
non-Ex installation, it should never be used in an Ex installation, as there is a danger that the
protective circuits have been inadvertently overloaded and no longer function correctly.
Connection via a load
resistor
Fig. 3-2: Connection via load resistor
Connection via HART
communication sockets
Fig. 3-3: Connection via a transmitter power supply with HART communication sockets (internal load resistor)
F5
F1
F2
F3
F4
OK
Field Xpert
+
-
+
-
HART device
Transmitter
power supply
e.g. RMA42
Status
Power
Load resistor
250 - 1100 Ohm
F5
F1
F2
F3
F4
OK
Field Xpert
Transmitter
power supply
RMA421
RMA422
RNS221
RN221
–
+
HART device
Status
Power
