SITRANS TH320/TH420 Temperature Transmitters

Why SITRANS TH320/TH420?

Designed for head-mount installation, SITRANS TH320 and TH420 combine universal sensor input, easy commissioning and seamless connectivity. TH320 efficiently covers core HART applications, while TH420 adds dual-input operation, drift detection and HART or PROFIBUS PA communication for higher availability. Versions for hazardous areas and safety-related applications support use in demanding plants.

Key benefits

Avoid downtime with automatic sensor backup

For high-availability applications, SITRANS TH420 keeps measurement running even if one sensor fails. Its dual-input design with hot backup switches automatically to the second sensor, maintaining continuous process visibility.

Commission and replace devices faster

Configuration via HART or PROFIBUS PA, stored parameter data and practical service functions reduce setup time and simplify replacement. This cuts commissioning effort and brings measuring points back into operation faster.

Improve accuracy and maintenance planning

Advanced diagnostics and, on SITRANS TH420, sensor drift detection help identify sensor issues early. Combined with sensor trim for precise matching, this supports faster calibration and more targeted maintenance.

Key details

Input	Resistance thermometers, thermocouples, resistance-type sensors, DC voltage sources
Output	4 ... 20mA (SITRANS TH320), HART (SITRANS TH320/420), Profibus PA (SITRANS TH420)
Operating temperature range	Standard: -50 … +85 °C (-58 … +185 °F); SIL: -40 … +80 °C (-40 … +176 °F)
Certificates/approvals	ATEX, IECEx, FM, CSA; EACEx, NEPSI, Inmetro; SIL 2/3 certification (HART only)
Usability/safety	Hardware and software write protection; uninterruptible loop current measurement for tests; alarm backup via 21mA error current
Accuracy/stability	Top input accuracy for Pt100 (IEC60751) +/- 0.04 °C; Stability: +/-0.05 °C (1year) or +/-0.18 °C (5 years); 2x 4-wire RTD connection (TH420)

Featured capabilities

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Built-in diagnostics for preventive maintenance

A bi-color LED shows local status. Input monitoring detects wire breaks and short circuits. SITRANS TH420 adds sensor drift detection. Self-monitoring and lifecycle diagnostics help localize faults and plan maintenance early.

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Loop checks without interrupting operation

Test terminals let you connect an ammeter anytime for monitoring and plausibility checks without opening the current loop, speeding up commissioning and service. Galvanic isolation ensures stable signals in demanding environments.

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High-availability design for critical applications

SITRANS TH420 supports dual 4-wire inputs with hot backup, switching automatically if a sensor fails. Callendar-van-Dusen sensor trim boosts accuracy. Rated to –40 °C with SIL 2/3 for HART, it suits harsh, safety-critical use.

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