Multi-Drop Mode - Emerson FB3000 Instruction Manual

Emerson FB3000 RTU Instruction Manual
D301851X012
October 2022
3.2.2

Multi-Drop Mode

In multi-drop mode, only the HART digital signaling (FSK – Frequency Shift Keying) is present and
no
4-20mA analog current signal is permitted (no AO allowed). Each device can support a
maximum 4mA bias current. Because the maximum rated output (sink) current of any 3HRT04
Module channel is 20mA, and each device can draw 4mA, a HART channel in multidrop mode
supports a total of 5 HART devices. With each of the 5 HART devices permitted to draw 4mA, the
sum of the currents is 20mA – the maximum current.
Figure 3-12
supports inputs, you cannot have multi-drop outputs.
You can wire each channel the same way to allow for up to 20 HART devices (5 per channel).
Figure 3-12. HART Wiring – Multi-Drop Mode on Channel 1
HD
52
shows how to wire a HART channel for multi-drop mode. Multi-drop mode only
HART Device
I/O Configuration and Wiring