Black Box IC108A Betriebsanweisung PDF herunterladen (Seite 10)

Advant

Smart Device (HART

) Interface User’s Guide

Chapter 1 Introduction

1-6 3BUR 001 085R0001 REV A

Conventional transmitters communicate with the Advant OCS via a 4-20 mA analog signal

proportional to the process variable being measured. This 4-20 mA signal requires analog to

digital conversion for the digitally based Advant OCS host to measure, display and control the

measured process variable. Smart devices (HART-compatible transmitters) can communicate

with the Advant OCS via analog and digital signals. Analog signals from smart devices are

communicated in the same manner as conventional devices, via a 4-20 mA signal. Smart devices

digitally communicate range limits and maintenance information in addition to the process

variable with the Advant OCS host via HART protocol using Frequency Shift Keying (FSK).

Since the FSK signal does not compromise the 4-20 mA signal of a smart device, the analog

(4-20 mA) signal and digital (FSK) signal for a smart device can co-exist on the same physical

twisted pair of wires.

To convert the HART FSK current to voltage which the SHIM can read, a dropping resistor is

used. The permitted range of the HART loop resistance is from 230 ohms to 1100 ohms.

Typically, a 250 ohm resistor is used.

NOTE

If connection units (S100 I/O), MTUs (S800 I/O) or TRIO blocks are not used for

SHIMs communicating only digital signals, a 250 ohm 1% 5W resistor is required

to provide the 250 ohm loop resistance.

When both analog and digital communication with smart devices is desired, the analog signal is

brought to the Advant controller using either S100 I/O, S800 I/O or Taylor



Remote I/O

(TRIO). Digital signals from up to four or eight smart devices are AC coupled from the smart

devices using a SHIM purchased from Arcom Control Systems, Inc. The SHIM facilitates

communication between the smart devices and the Advant OCS by converting the HART

protocol used by the smart devices to the ModbusB protocol used by the Advant OCS. The

SHIM also converts the HART protocol physical/link layers signals to RS-232 (optionally to

RS-485 with converter) signal levels respectively used for Advant Controller serial

communication.

An AC410 node can be equipped with either one or two CI532V02 ModbusB Multi-vendor

Interface(s) (MVI), which have two ports each. Each RS-232 port is provided by connection

between these modules, a SHIM, and up to eight smart devices connected to each SHIM. If an

RS-232 to 485 converter is used, then up to 31 SHIMs can be connected to a port with up to

eight smart devices connected to each SHIM, depending on performance requirements.

An AC 460 node can have up to three redundant PM510 CPU sets with up four CI532V02

ModbusB Multi-vendor Interface(s) (MVI) per PM510 CPU set. Each RS-232 port is provided

by connection between these modules, a SHIM, and up to eight smart devices connected to each

SHIM. If an RS-232 to 485 converter is used, then up to 31 SHIMs can be connected to a port

with up to eight smart devices connected to each SHIM, depending on performance

requirements.

NOTE

Communications redundancy for the Smart Device Interface is not available,

therefore, there is no automatic port switching upon failure of the Advant OCS to

SHIM connection.

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