Emerson Smart Wireless THUM Adapter Reference Manual page 7

Reference Manual
00809-0100-0775, Rev AA
March 2009
Considerations
General
Commissioning
Mechanical
Electrical
The Smart Wireless THUM Adapter is connected to a HART sub-device. With simple HART configu-
ration, the THUM transmits the HART information from the sub-device unto the WirelessHART net-
work.
The THUM can be commissioned before or after installation. It may be
useful to commission it on the bench, before installation, to ensure proper
operation and to become familiar with its functionality. When applicable, make
sure the instruments are installed in accordance with intrinsically safe or
non-incendive field wiring practices. The device will be powered whenever THUM is
connected to a powered loop.
Location
When choosing an installation location and position, take into account the
need for access to the transmitter. For best performance, the antenna should
be vertical with some space between objects in a parallel metal plane such as
a pipe or metal framework, as the pipes or framework may adversely affect
the performance of the antenna.
THUM Power Options
The THUM has two power options; variable current, and fixed current mode.
Variable Current
Variable current mode is the mode that the THUM should be in if the current on the 4-20 mA loop can
change between 4 to 20 mA. The THUM will drop 2.25 volts at 2.5 mA and 1 volt at 25 mA. The
voltage drop is linear between these two points. The THUM will operate
according to standard specifications under this mode.
Fixed Current
Fixed current mode can only be used when the current of the loop will never fall below 20 mA. The
THUM will always drop 1 volt across the loop. If the current of the loop falls below 20 mA the
THUM, and the rest of the wireless network may not function properly.
This symbol represents protective earth grounding.
Smart Wireless THUM Adapter