ST420-4

Overview

The ST420-4 is an analog-output shaft speed sensor and transmitter manufactured by Electro-Sensors. It detects magnetic pulses from a rotating shaft-mounted pulser target, such as a disc or wrap. The device outputs a 4-20mA analog signal proportional to the rotational speed. It operates on a nominal loop voltage of 8-30 VDC with a minimum input of 8V and maximum of 30V. The sensor features a compact cylindrical design measuring 80 mm (3.15 inches) in length and 18 mm (0.71 inches) in diameter. The recommended sensor gap is 1/4 inch ± 1/8 inch.

Feature Summary

• Combines magnetic pulse detection, signal processing, and two-wire loop-powered output in a single unit
• Provides a standard 4-20mA analog signal directly proportional to shaft speed
• Designed for direct mounting near rotating shafts with minimal air gap requirements

Applications

• Industrial machinery shaft speed monitoring
• Rotating equipment tachometry
• Process control systems requiring analog speed feedback

Procurement Notes

Verify that the specific part number ST420-4 matches the required output signal range and voltage specifications for your application. Confirm compatibility with the existing pulser target type and installation gap constraints. Ensure the power supply provides the necessary 8-30 VDC loop voltage. Check for any specific environmental ratings if operating in harsh conditions.

Selection Notes

Select this model when a two-wire, loop-powered analog speed sensor is required. It is suitable for applications where space is limited due to its compact cylindrical form factor. Ensure the rotating target generates sufficient magnetic pulses within the specified gap range. Verify that the downstream controller accepts a 4-20mA input signal.

Part Context

The ST420 series consists of analog-output shaft speed sensors designed for industrial environments. These devices integrate sensing and transmission capabilities into a rugged housing. The series is commonly used in automation and monitoring systems where reliable speed data is critical for operational safety and efficiency.

Replacement Considerations

Public confirmed substitute part numbers are not available in the provided documentation. Consult the manufacturer's official cross-reference guide for verified replacements.