MACTek BULLET™ – User Manual
DM1101010UAB
Copyright 2009-2010
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Power
The Bullet WirelessHART Adapter has been designed to be extremely power efficient
and flexible to allow for a wide variety of installation options.
Loop Powered Mode
The Bullet can be wired in series with devices on a 4-20mA loop and be powered from
the loop. The Bullet utilizes MACTek’s patent pending
StepVolt™
technology, to allow
the user to set this insertion voltage drop between 1.0 – 2.5 Volts, in 0.5 Volt increments.
StepVolt™ allows users to select the best insertion voltage drop for their application.
The higher the voltage drop setting used, the more WirelessHART messages the Bullet
will be able to transmit and receive.
In applications where there is very little voltage overhead in the loop, such as
transmitters on very long cable runs or with IS barriers, StepVolt™ allows the selection
of a low insertion voltage drop. However in a number of applications there is plenty of
voltage overhead on the loop to allow for a high voltage insertion drop from the Bullet.
A concern with a loop powered WirelessHART Adapter is being able to operate under
worst case conditions since very little power is available to be used by the Adapter at low
loop current conditions. The Bullet is designed to operate at the worst case operating
conditions at all power settings and will respond to Wired or WirelessHART commands.
The Bullet will operate as specified with reliable communications even under the
following conditions:
-
Loop current of 3.2mA and 1.0V insertion voltage drop
-
Temperature Extremes (-40C to +85C)
- Worst Case wired-HART communication on the loop. Constant wired-HART
communication addressed to the Adapter and the Adapter responding to every
command.
-
Every WirelessHART timeslot filled and transmitting
Note: On power-up, the voltage drop will be set to 1.0V until the Bullet has finished
initialization. At this point, it will change the voltage drop to the value specified.
NOTE: The Bullet cannot control the loop current, if connected in loop-powered mode
there must be something controlling the loop current, such as a 4-20mA transmitter.
StepVolt™ Benefits
The benefit to using a high StepVolt™ setting is that the Bullet will be able to support a
much higher amount of WirelessHART packets per second. Even if the particular device
attached to the Bullet is configured for a very low update rate, being able to support a
high amount of WirelessHART packets per second helps the overall WirelessHART
network operation.
