User manual

Reference MVI56-HART ♦ ControlLogix Platform
User Manual HART Multi-drop Master Communication Module
Page 104 of 171 ProSoft Technology, Inc.
October 13, 2011
5.7.1 Notes
1 All four 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 all four 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.