Honeywell STT173-BS

Technical Dossier

Product Details And Specifications

Honeywell STT 3000 Series Technical Notes

The Honeywell STT 3000 series represents one of the most widely deployed families of smart temperature transmitters in global heavy industry. Installed across petrochemical complexes, nuclear power stations, crude oil refineries, pulp and paper mills, and LNG terminals, the STT 3000 platform has maintained a dominant position in process instrumentation for over three decades. Its HART and FOUNDATION Fieldbus communication options, combined with SIL 2-capable variants, have made it the default specification for safety-instrumented systems (SIS) and distributed control system (DCS) loops in facilities operated by ExxonMobil, Shell, BASF, Sinopec, and comparable tier-1 operators. The transmitter family covers thermocouple, RTD, millivolt, ohm, and potentiometer inputs, providing a single hardware platform for virtually all temperature measurement requirements in a process plant.

The Evolution of STT 3000 Architecture

The STT 3000 architecture was introduced by Honeywell in the early 1990s as a successor to the STT100 and STT150 analog transmitter lines. The first-generation STT 3000 units used a two-wire 4–20 mA loop with superimposed HART protocol, establishing the baseline communication model that persists across all subsequent revisions. The STT35F and STT350 variants introduced FOUNDATION Fieldbus H1 support, enabling direct integration into Honeywell Experion PKS and TPS/TDC 3000 DCS architectures without analog-to-digital conversion at the marshalling cabinet.

The second-generation platform, represented by the STT170 and STT173 sub-families, introduced enhanced EMC shielding, expanded input range tables, and a revised LCD indicator module. The STT173-BS specifically incorporates a stainless-steel housing rated for ATEX Zone 1 / IECEx explosive atmospheres, making it the standard selection for offshore platforms and chemical reactor areas. The STT700 series, introduced in the 2010s, added WirelessHART capability and extended the SIL rating to SIL 3 for select configurations, representing the current-generation replacement path for legacy STT 3000 installations.

Compatibility between generations is maintained at the process connection and conduit entry level, but electronics modules and LCD assemblies are not interchangeable across all sub-families. Facilities managing mixed-generation fleets must maintain separate spare parts inventories for STT170/STT173 and STT700 electronics.

STT 3000 Full Catalog & Functionalities (SKU List)

HART 4–20 mA Transmitters

• STT173-BS: HART smart temperature transmitter, stainless-steel housing, ATEX/IECEx Zone 1, universal input (TC/RTD/mV/Ω)
• STT173-A: HART smart temperature transmitter, aluminum housing, general-purpose, universal input
• STT173-E: HART transmitter, epoxy-coated aluminum, enhanced corrosion resistance, universal input
• STT173-H: HART transmitter, high-ambient-temperature variant, rated to +85°C ambient, universal input
• STT170-A: First-generation HART transmitter, aluminum housing, predecessor to STT173 series
• STT170-BS: First-generation HART transmitter, stainless-steel housing, ATEX Zone 1
• STT35F-A: FOUNDATION Fieldbus H1 transmitter, aluminum housing, universal input, FF-compliant function blocks
• STT35F-BS: FOUNDATION Fieldbus H1 transmitter, stainless-steel housing, ATEX/IECEx Zone 1
• STT350-A: Enhanced FOUNDATION Fieldbus transmitter, aluminum housing, extended diagnostics
• STT350-BS: Enhanced FOUNDATION Fieldbus transmitter, stainless-steel housing, ATEX Zone 1

SIL-Rated & Safety Variants

• STT173-SIL-A: SIL 2-capable HART transmitter, aluminum housing, IEC 61508 certified
• STT173-SIL-BS: SIL 2-capable HART transmitter, stainless-steel housing, ATEX Zone 1, IEC 61508 certified
• STT700-A: Current-generation HART/WirelessHART transmitter, SIL 3 capable, aluminum housing
• STT700-BS: Current-generation HART/WirelessHART transmitter, SIL 3 capable, stainless-steel housing

Accessories & Display Modules

• STT-LCD-01: Plug-in LCD indicator module for STT170/STT173 series, 5-digit display
• STT-LCD-02: Enhanced LCD indicator module for STT350/STT700 series, configurable display
• STT-CONF-01: Local configuration keypad module, compatible with STT173 and STT350 series

Sourcing Hard-to-Find & Obsolete STT 3000 Parts

Honeywell has progressively transitioned the STT 3000 product line toward the STT700 platform. The STT170 sub-family reached end-of-manufacture status, and the STT173 series is in a managed availability phase, with Honeywell directing new projects toward STT700. For operating facilities with installed STT170 and STT173 units, replacement electronics, LCD modules, and terminal block assemblies are no longer available through standard distribution channels in many regions.