ProSoft Technology MVI69-HART - Manual (Page 159)

MVI69-HART ♦ CompactLogix Platform Reference
HART Multi-drop Master Communication Module User Manual
ProSoft Technology, Inc. Page 159 of 169
March 29, 2012
5.10 Example Field Terminations
Up to 15
instruments per
channel One instrument per channel
Multi-drop Mode
(address 1 to 15) Point to Point
Mode
(address 0 to 15) Point to Point
Mode with
Analog
(address 0 only)
Power Mode A
24VDC connected
to HART power
terminals 1 and 2
on terminal block
Master Powered
instruments on all
4 channels
OK
Install 250Ω 1KΩ OK
Install 1K resistor OK
Power Mode B
HART power
terminals 1 and 2
on terminal block
left open
Loop Powered
instruments on 1
or more channels
OK OK OK
- differential or
single ended
analog signal
Self Powered
instruments on 1
or more channels
Not possible OK OK
-differential or
single ended
analog signal
5.10.1 Notes
1 Both channels on the unit must be either Master Powered (Power Mode A) or
must be Loop or Self powered (Power Mode B). You cannot mix Power Mode
A and Power Mode B on the same unit. You can mix Loop powered and Self
powered instruments on the same unit. However, you cannot mix Loop
powered and Self powered instruments on the same channel.
2 For Master Powered, Multi-drop Mode and Point to Point Mode, a 1K, 1W
resistor must be connected across the + and - input terminals of each HART
channel. Resistors are supplied with each product.
3 When configuring loop powered instruments in a Power Mode B type multi-
drop network, use only one power supply per HART channel if you wish to
maintain channel to channel isolation. If channel to channel isolation is not
required, the same power supply may be used for both channels. However, a
separate series resistor is required for each channel. An appropriately sized
resistor must be connected in series with the power supply for each channel.
The value and power rating of the resistor is dependant upon the number of
instruments in the loop and the length and gauge of the pair of wires
connecting the instruments to the unit. 250 Ohm, 3 Watt is a good, first
choice value.
4 If field instrument wiring is shielded, terminate shields at the ground terminals
of the HART connector. Do not terminate the shields at the instrument.