Honeywell Process Solutions · Temperature Instruments

SmartLine STT850 Temperature Transmitter

Part number STT850-A-1-A-0-A-1-A-0-AHB-11S-A-50A0-0000

Field-mount dual-input temperature transmitter, ±0.1 °C accuracy, sensor redundancy and drift alarms, SmartLine modular housing, HART 7 / FF, SIL2/3.

CE
ATEX
IECEx
SIL2
HART 7

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Overview

The STT850 brings the SmartLine modular platform to temperature: the same housing, display and communication modules as the ST800 pressure transmitters, which simplifies spares. It accepts two RTD or thermocouple inputs with redundancy, differential, average and drift-alarm functions, and delivers ±0.1 °C accuracy with Pt100 sensors. The advanced display can show both sensors and a trend, and maintenance-mode messages help technicians during loop checks. HART 7 and FOUNDATION Fieldbus versions are available, with SIL2/3 certification for safety loops.

Key features

Dual RTD/TC inputs with redundancy, differential, average and drift alarm
Accuracy ±0.1 °C (Pt100), 2-year stability ±0.05 °C
SmartLine modular housing shared with ST800 pressure transmitters
4–20 mA HART 7 or FOUNDATION Fieldbus; basic or advanced display
SIL2/3 per IEC 61508; ATEX, IECEx, FM, CSA flameproof and intrinsically safe

Typical applications

Critical reactor and column temperature points
Boiler, turbine and furnace temperature monitoring
Safety instrumented functions requiring redundant sensors
Experion-standardized plants wanting common spares

Industries

Technical specifications — STT850-A-1-A-0-A-1-A-0-AHB-11S-A-50A0-0000

Measurement
Inputs	2 × RTD (2/3/4-wire), TC (B, E, J, K, N, R, S, T), ohm, mV
Accuracy	±0.1 °C (Pt100)
Dual functions	Redundancy, differential, average, drift alarm
Output
Signal	4–20 mA HART 7 or FF
Display	Basic or advanced graphic display
Power	11–42 V DC
Process
Mounting	Field, pipe or wall; conduit entries 1/2 NPT or M20
Housing	Aluminium or 316 SST, single or dual compartment
Environment
Ambient temperature	-40…+85 °C
Enclosure	IP66/67, NEMA 4X

Specifications are summarised from the manufacturer's documentation for selection purposes. Always confirm against the current datasheet before design-in; we send the datasheet and the exact ordering code with every quotation.

Related part numbers and alternatives

Part number	Relationship
`STT750`	SmartLine STT750 — economy field-mount transmitter	Quote
`STT700`	DIN-rail / head-mount transmitter for non-critical points	Quote
`3144P`	Rosemount field-mount alternative	Quote

Not sure which variant you need? Send us the nameplate photo or the old part number and we will identify the current equivalent.

Supply, documentation and lead time

What you receive

Genuine Honeywell Process Solutions product in original packaging
Commercial invoice and packing list; Certificate of Conformance on request
Datasheet, declaration of conformity and country of origin as issued by the manufacturer
Manufacturer warranty, period stated on the quotation

How we quote

Reply within one business day with price, lead time and stock position
Alternatives proposed when they improve price or delivery
Incoterms of your choice: EXW Hai Phong, FOB/FCA, CIF/DAP to your site
Consolidated shipments for multi-line orders; export documentation for buyers outside Vietnam

Indicative HS code 9025.19 — final classification is confirmed on the commercial invoice.

Frequently asked questions

Is the STT850 compatible with existing SmartLine ST800 spares?

Yes. The housing, displays and communication modules are shared across the SmartLine range, so a plant can hold one set of display and electronics spares for pressure and temperature.

Can I use two different sensor types on one STT850?

Yes. Each input is configured independently, so an RTD and a thermocouple can be combined, for example to use the RTD for accuracy and the thermocouple as high-temperature backup.

Is the STT850 available from stock, and what is the lead time?

Typical factory lead time is 3–6 weeks. We confirm with the quotation.