WESTINGHOUSE ST24B3 Temperature Transmitter

The WESTINGHOUSE ST24B3 is a robust, industrial-grade temperature transmitter designed for precise and reliable process monitoring. As a key component in measurement and control loops, it interfaces directly with Resistance Temperature Detector (RTD) sensors, typically Pt100 types. Its primary function is to convert the small resistance change from the RTD into a standardized, noise-immune 4-20 mA analog signal. This signal is then transmitted over long distances to programmable logic controllers (PLCs), distributed control systems (DCS) like Westinghouse Ovation, or chart recorders, enabling accurate temperature monitoring and control in demanding industrial environments.

Product Function and Design Principle

The ST24B3 operates on the standard 2-wire transmitter principle, where the same pair of wires carries both the DC power supply (typically 24 VDC) and the output current signal. This design simplifies installation and reduces wiring costs. The transmitter incorporates a stable excitation current for the RTD, precise signal conditioning circuitry, and a linearization algorithm specific to the RTD's temperature-resistance curve. It compensates for lead wire resistance and provides electrical isolation between the sensor circuit and the output loop, protecting sensitive control system inputs from ground loops and voltage surges common in plant environments. Housed in a durable, compact enclosure, it is often designed for direct head-mounting on a thermowell or for rail mounting in a control cabinet.

Typical Technical Specifications

Primary Industrial Applications

Installation and Integration

Installation involves connecting the RTD sensor wires to the transmitter's input terminals and wiring the 24 VDC power supply in series with the 4-20 mA input of the receiving controller (PLC/DCS). Proper grounding and the use of shielded cable are recommended for optimal noise immunity. The transmitter's range may need to be configured to match the expected process temperature. Its robust design allows for installation directly at the measurement point, even in outdoor or harsh locations, minimizing sensor lead length and potential signal degradation.