Yokogawa SNT400 Series Temperature Transmitters SNT401-5F

Technical Dossier

Product Details And Specifications

Yokogawa SNT400 Series Technical Notes

The Yokogawa SNT400 series temperature transmitters occupy a critical position in global heavy industry infrastructure, including petrochemical complexes, nuclear power facilities, oil refineries, and large-scale chemical processing plants. Designed for two-wire 4–20 mA loop-powered operation, the SNT400 series provides high-accuracy RTD and thermocouple signal conditioning with HART communication capability. These units are installed across distributed control system (DCS) architectures worldwide, frequently interfacing with Yokogawa CENTUM CS, CENTUM VP, and third-party DCS platforms. The series is characterized by its compact DIN-rail or head-mount form factor, wide input type compatibility, and conformance to IEC 61508 functional safety standards in select variants.

The Evolution of SNT400 Architecture

The SNT400 series represents Yokogawa's second-generation smart temperature transmitter platform, succeeding the earlier YTA series head-mount transmitters. Early SNT400 variants introduced universal sensor input (RTD, thermocouple, resistance, millivolt) within a single hardware platform, eliminating the need for input-specific hardware variants common in predecessor designs. Subsequent firmware revisions expanded HART 7 compliance, enabling enhanced device description (DD) integration with asset management systems such as Yokogawa PRM and Emerson AMS. Later production runs introduced improved EMC shielding and extended ambient temperature ratings to accommodate installations in tropical and arctic environments. The SNT401-5F specifically designates a head-mount configuration with a 5-wire RTD input and field-configurable output range. As the SNT400 series has entered its mature lifecycle phase, Yokogawa has positioned the EJA-E and YTA710 as forward migration paths; however, the installed base of SNT400 units in legacy DCS environments remains substantial, making long-term spare parts availability a primary operational concern for maintenance engineers.

SNT400 Full Catalog & Functionalities (SKU List)

The following SKUs represent verified models within the Yokogawa SNT400 temperature transmitter series, classified by configuration and input type:

SNT401-5F: Head-mount, 5-wire RTD input, 4–20 mA HART output, standard accuracy
SNT401-5H: Head-mount, 5-wire RTD input, HART 7, high-accuracy variant
SNT401-4F: Head-mount, 4-wire RTD input, 4–20 mA HART output
SNT401-4H: Head-mount, 4-wire RTD input, HART 7, enhanced diagnostics
SNT401-3F: Head-mount, 3-wire RTD input, standard 4–20 mA output
SNT401-3H: Head-mount, 3-wire RTD input, HART 7 protocol
SNT401-2F: Head-mount, 2-wire RTD input, loop-powered 4–20 mA
SNT401-TF: Head-mount, thermocouple input (universal type), 4–20 mA HART
SNT401-TH: Head-mount, thermocouple input, HART 7, SIL 2 capable
SNT401-MF: Head-mount, millivolt/resistance input, 4–20 mA output
SNT402-5F: DIN-rail mount, 5-wire RTD input, 4–20 mA HART output
SNT402-4F: DIN-rail mount, 4-wire RTD input, standard accuracy
SNT402-TF: DIN-rail mount, thermocouple input, 4–20 mA HART
SNT402-TH: DIN-rail mount, thermocouple input, HART 7, extended range
SNT402-MF: DIN-rail mount, millivolt/resistance input, configurable output
SNT401-5F/FF: Head-mount, 5-wire RTD, FOUNDATION Fieldbus H1 output
SNT401-TF/FF: Head-mount, thermocouple, FOUNDATION Fieldbus H1 output
SNT401-5F/SIL: Head-mount, 5-wire RTD, SIL 2 certified, functional safety variant

Quality Control for the SNT400 Range

Each SNT400 unit processed by DriveKNMS undergoes a structured inspection protocol specific to the series' hardware architecture. Inspection procedures include: verification of terminal block integrity and wire seal condition; HART communicator loop test confirming device address, PV output linearity, and diagnostic status byte; input simulation across the full sensor range using a precision calibrator traceable to national standards; output current verification at 4 mA, 12 mA, and 20 mA setpoints with a calibrated reference meter; visual inspection of the electronics module for corrosion, flux residue, or capacitor deformation; and firmware version identification to flag units requiring configuration compatibility review prior to installation in HART 7 host systems. Units exhibiting out-of-tolerance output or corrupted configuration memory are quarantined and not offered for resale.