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1.1.2.2
Multipoint connection (Multidrop). Multiple slaves connected in parallel.
HART’s addressing system can handle 15 devices whereby they are wired in parallel. In this case, the current is the sum of the currents of all the devices in the loop,
which has not informative value. So in this case, the output current of the transmitters should be set to multidrop mode, which means a constant current of 4mA. This
automatically happens when the polling address is set between 1..15. (if the polling address is 0, then we should have only one transmitter with 4…20mA output, if
the polling address is 1…15, then we will have a constant 4 mA). There is a deviation possibility for transmitters whose output current can be programmed to an
arbitrary fixed value, however in this case, the minimal voltage drop on the terminal of the transmitters must be the minimum specified voltage, otherwise the
transmitter(s) will not be able to work (measure or respond)
T
1
ransmitter
Transmitter 2
T
3
ransmitter
T
15
ransmitter
I+
I–
SH
L+
L–
MultiCONT
250
+Us
....
Universal interface
RS485
820
*
In a Multidrop system, the „burst mode” does not work
* An 820 ohm resistor should be connected between the L- and SH terminals of the Ex version MultiCONT when it is used with the 3 (max. allowed) Ex version
MicroTREK microwave level transmitter.
Содержание MultiCONT
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