Description The ST420 is an analog-output shaft speed sensor. It detects magnetic pulses from a rotating shaft-mounted pulser disc or wrap and outputs a smooth, continuous 4-20mA analog signal in direct proportion to the rotating shaft speed. (See the Output Function Graph on back page) The ST420 combines a magnetic pulse detector, signal processing and 2-wire loop-powered 4-20mA circuitry into a stainless steel M18x1 sensor housing. Also available, ST420-DI with built-in 1/2” NPT conduit port. The ST420, when used with an approved I.S. barrier, is UL listed as intrinsically safe for use in Class I (Groups C & D) and Class II (Groups E, F & G). The ST420-DI, with its built-in conduit port, is designed to be Class II (Groups E, F & G) dust ignition-proof for use with conduit. Product Information Dimensional Drawings • ST420 • ST420-DI 6111 Blue Circle Drive Minnetonka, MN 55343 Phone: 952-930-0100 Fax: 952-930-0130 ISO9001:2000 Certified Free Catalog and Application Assistance 1-800-328-6170 Visit Us Online: www.electro-sensors.com ST420 Loop-Powered 4-20mA Shaft Tachometer • 2-wire loop-powered 4-20ma analog shaft speed sensor • Accurate quartz crystal based digital processing • No user calibration — works right out of the box • Standard and custom measurement ranges available • Intrinsically safe design • Works with shaft-mounted pulser targets (disc/wrap) • Stainless Steel M18x1 housing, NEMA 4X/IP67 • Reverse wiring protected ST420-DI ST420

ST420 Shaft Tachometer Specifications subject to change without notice. ES-735 Rev C 6111 Blue Circle Drive Minnetonka, MN 55343 Phone: 952-930-0100 Fax: 952-930-0130 ISO9001:2000 Certified Free Catalog and Application Assistance 1-800-328-6170 Visit Us Online: www.electro-sensors.com Specifications Sensor Gap . . . . . . . . . . . . . . . . . . . . . . 1/4” ± 1/8” Vin (min max) . . . . . . . . . . . . . . . . . 8-30 Vdc (nominal loop power: 24 Vdc) Operating Temp . . . . . . . . . . . . . . . . . -20°C +85°C (-4°F 185°F) Accuracy . . . . . . . . . . . . . . . . . . . . . . . Max error at 25°C...