FB3000 RTU HART
®
I/O Module Field Installation Guide
D301918X012
June 2021
6
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 2
shows how to wire a HART channel for multi-drop mode. Multi-drop mode only 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 2. HART Wiring – Multi-Drop Mode on Channel 1
HD
HART Device
Summary of Contents for FB3000
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