Is it possible to multi-drop the Hart modules on an SC200?
Multi-drop the Hart modules on an SC200
The HART Communication Module can be configured for Multidrop mode by configuring the HART address for the output >0 or for Point-to-Point (Single Drop) mode by configuring the HART address for the output to 0 (refer to pages 5-6 of the attached HART PROTOCOL.pdf). If the output is configured for Multidrop mode (HART address >0), then the analog output is held at 4 mA. To prevent damage, we would recommend wiring using the externally/loop powered output terminals in the SC200 and powering with an auxiliary power supply as shown below (also refer to pages 4-9 of the sc200 HART Communications Module User Manual), this will allow the network segment to accommodate up to 15 field devices. With this wiring scheme Output A and Output B can be "daisy chained" together (Output C is not HART enabled) and have a single pair of wires running to the loop power supply and data acquisition system or HART Communicator.
Each sensor would be configured with it's own unique HART address, and the user would send separate HART commands to request the data from each sensor individually.
If the output is configured for Point-to-Point (Single Drop) mode, the analog output can be configured to represent a selected control parameter (PV or SV) and the digital signal over the same pair of wires can simultaneously communicate all available standardized application layer data (Device Status & Diagnostic Alerts, Process Variables & Units, Basic Configuration Parameters, Manufacturer ID & Device Tag, Loop Current & % Range). Refer to the attached sc200 HART Commands Beta.xls and specifically the sc200 Controller commands and pH_ORP D586 worksheets.