Endress+Hauser Preline RN 221N Betriebsanleitung Seite 21

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3.3 HART -operating unit connection
The communication resistor required for SMART transmitters is
already available in the unit and can easily be connected into
the current circuit. This means that communication with the
connected transmitter can be done, without interrupting the
measurement circuit, by simply connecting the HART
operating unit to the front mounted communication sockets.
3.4 Connecting external sensors (input)
If there is a possibility of electrical transients on long signal
cable runs we would recommend that an overvoltage protection
unit is used. The unit has a built in loop power supply that is
galvanically isolated from the signal input. This means that
there is no need for any external components to power any
transmitters connected.
Loop power supply with
passive ccurrent output,
when using the loop power
supply from the unit.
Active barrier
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HART - connection sockets
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