Compact ST420 Shaft Tachometer Delivers Plug-And-Play, High-Accuracy Shaft Speed Monitoring


Electro-Sensors, Inc. announces the ST420, a loop-powered, stainless steel analog shaft tachometer. The ST420 requires no user calibration, providing a dependable shaft speed monitoring solution right out of the box. The rugged, compact ST420—only 18mm in diameter—reliably detects magnetic pulses from a rotating shaft-mounted pulser disc or wrap.

Then, the ST420 uses quartz crystal-based digital processing to convert pulses to a smooth, continuous 4-20mA analog signal directly proportional to the pulse frequency. The result is a plug-and-play solution that allows users to accurately and simply monitor rotating shaft speed in industrial applications.

The ST420 shaft tachometer has been tested by UL to the standards UL913 and CAN/CSA C22.2 No 157-92 (Intrinsic Safety), assuring it provides an intrinsically safe solution for Class I (Groups C & D) and Class II (Groups E, F & G) environments, when used with an approved I.S. barrier. Its magnetic pulse detector, signal processing capability and 2-wire loop-powered 4-20 mA circuitry are combined into a robust stainless steel M18x1 sensor housing. With this durable construction, the ST420 resists harsh plant environments and is rated NEMA 4X/IP67.

Also available is the ST420-DI* shaft tachometer, which delivers reliable shaft speed monitoring by incorporating the above features into a rugged M18x1 sensor housing with a built-in ½" NPT conduit port. This dust ignition-proof model is designed for Class II (Groups E, F & G) environments.

Applications: Offering both standard and custom measurement ranges, the ST420 facilitates precise shaft speed monitoring in industries including:
Grain processing
Bulk materials handling
General manufacturing
Ethanol/biofuels processing
Power generation plants
Water utilities
Food processing
Textile production

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