PLX51-HART-4I / PLX51-HART-4O
♦
HART Input/Output
Installation
Multidrop Field Devices
User Manual
ProSoft Technology, Inc.
Page 16 of 127
Figure 2.13 – Channel Connection - 2-wire – Externally Powered with External Resistor
2.5 Analog (HART) – Multidrop
In a multidrop setup the field devices can be connected in either a series or parallel
configuration. The maximum number of devices that can be connected per channel is
as follows:
Table 2.2 - Maximum Device Count
Connection Method
PLX51-HART-4I
PLX51-HART-4O
Series
2
2
Parallel
7
5*
Note:
Output devices must be limited to 4 mA.
The above table should be considered as a maximum count, lower counts may be
applicable for some field devices.
2.5.1 Series Configuration
The series connection method has the advantage of the (4-20 mA) current still being
controlled by one of the devices, which may be required in some applications. The
disadvantage is that the supply voltage is divide by the devices, so the maximum
would typically be 2. (Assuming a typical minimum of 10V, and a supply of 24V).
This would apply to each channel of both the PLX51-HART-4O and the PLX51-
HART-4I.
As indicated in the diagrams below, the PLX51-HART-4I can support multidrop
devices in series with either module-powered or externally-powered configurations.
Figure 2.14 – PLX51-HART-4I - Multidrop Wiring – Series – Module Powered