Section 2 - Description And Operation; Introduction; Functional Operation; Physical Operation - ABB STT04 Instruction Manual

SECTION 2 - DESCRIPTION AND OPERATION

INTRODUCTION

FUNCTIONAL OPERATION

HART
ABB FSK

PHYSICAL OPERATION

This section describes the operational modes of the STT04 Smart
Transmitter Terminal and contains diagrams of the wiring connections
between the field device and the terminal.
The STT04 terminal operates with a field device by attaching clip
leads from the terminal to the signal wires of the field device. Commu-
nication occurs over the signal wires.
The STT04 terminal and field devices communicate by using any of
the following communication methods:
A slow speed (1,200 baud) communication standard established by
HART communications foundation (specification 5.0). The communi-
cation signal is a high frequency AC waveform with a zero DC aver-
age. It has no effect on the transmitter output. This communications
method provides exceptional noise immunity.
High speed (9,600 baud) frequency shift keying is a form of frequency
modulation used for digital communication. The communication sig-
nal is a high frequency AC signal with a DC average of zero. There-
fore, digital communication and process variable output can occur
simultaneously. Communicates with up to eight devices when inter-
facing the ABB digital field bus.
The STT04 terminal connects to the field device anywhere there is
access to the signal leads of the transmitter. The STT04 terminal
must be connected between the device and the 250 ohm resistance.
The clip leads connect across the signal leads independent of signal
direction or polarity. Refer to Figures
Batteries and length of charge can be operated with the charger con-
nected.
2-1 and 2-2.
INTRODUCTION
2 - 1