The WESTINGHOUSE ST24B3 is an industrial-grade temperature transmitter, commonly paired with an RTD (Resistance Temperature Detector) sensor. It is designed to provide accurate and stable temperature measurement by converting the resistance signal from an RTD probe into an isolated 4-20 mA current loop signal for use in distributed control systems (DCS) and PLCs.
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.
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.
High Accuracy and Stability: Provides precise temperature measurement with low drift over time, ensuring long-term reliability for critical processes.
RTD Sensor Compatibility: Specifically designed for use with standard Pt100 RTDs (and sometimes other types like Pt1000), covering wide temperature ranges.
Linearized 4-20 mA Output: Delivers a standardized, linear current output directly proportional to temperature, which is the industry standard for process control communication.
Two-Wire Loop Powered Design: Simplifies installation by requiring only two wires for both power and signal, reducing infrastructure complexity.
Electrical Isolation: Features input/output/power isolation to prevent ground loop issues and protect connected equipment from transients.
Rugged Industrial Construction: Housed in a robust casing suitable for harsh environments, with ratings for temperature, humidity, and often chemical exposure.
Configurable Range: Often allows for limited field configuration of the temperature span (e.g., via DIP switches) to match specific application needs.

Based on Common Industry Specifications for this Product Type:
Input Sensor: Pt100 RTD (3-wire or 2-wire connection typical).
Temperature Range: Configurable span, covering typical industrial ranges (e.g., -50°C to +500°C).
Output Signal: 4-20 mA DC, two-wire, linear to temperature.
Power Supply: 12-36 VDC (standard 24 VDC loop power).
Accuracy: High accuracy class (e.g., ±0.1% of span or better).
Ambient Temperature Rating: -40°C to +85°C (for the transmitter head).
Electrical Isolation: 500 Vrms or higher between input, output, and power.
Enclosure Rating: Typically IP65 or NEMA 4X for environmental protection.
Mounting: Head-mount for thermowell connection or DIN-rail mount.
The WESTINGHOUSE ST24B3 transmitter is utilized across various industries for critical temperature measurement:
Power Generation: Monitoring bearing temperatures, winding temperatures in motors and generators, and fluid temperatures in cooling systems.
Oil & Gas and Petrochemical: Measuring process stream temperatures in pipelines, distillation columns, reactors, and storage tanks.
Chemical and Pharmaceutical Manufacturing: Providing precise temperature data for batch reactors, heat exchangers, and drying processes to ensure product quality and safety.
HVAC and Building Management: Monitoring air and water temperatures in large-scale heating, ventilation, and cooling systems.
Food and Beverage Processing: Ensuring proper temperatures in pasteurization, sterilization, and fermentation processes.
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.
The WESTINGHOUSE ST24B3 temperature transmitter is a reliable and accurate workhorse for industrial temperature measurement. By providing a robust interface between fragile RTD sensors and industrial control systems, it ensures that critical temperature data is transmitted faithfully and reliably. Its simplicity, durability, and adherence to the universal 4-20 mA standard make it a trusted component for engineers seeking to maintain process efficiency, safety, and quality in a wide array of industrial automation applications.



