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ST420 Shaft Tachometer

ST420 Shaft Tachometer

Product catalog summary

Overview
The ST420 is an analog-output shaft speed sensor designed to detect magnetic pulses from a rotating shaft-mounted pulser disc or wrap. It outputs a continuous 4-20mA analog signal proportional to the shaft speed. The device integrates a magnetic pulse detector, signal processing, and 2-wire loop-powered circuitry within a stainless steel M18x1 housing. An alternative model, the ST420-DI, includes a built-in 1/2” NPT conduit port.

Specifications
- Sensor Gap: 1/4” ± 1/8”
- Voltage Input: 8-30 Vdc (nominal loop power: 24 Vdc)
- Operating Temperature: -20°C to +85°C (-4°F to 185°F)
- Accuracy: Max error at 25°C ± 0.25%; Max error over operating temperature ± 0.50%
- Output Response Time: Less than 9ms
- Cable: 24AWG, 10 feet length, Brown (V+), Black (V-)
- Dimensions: ST420: 80mm long x 18mm dia.; ST420-DI: 95mm long x 18mm dia.

Protection and Safety
The ST420 is intrinsically safe for use in Class I (Groups C & D) and Class II (Groups E, F & G) environments. The ST420-DI is designed to be dust ignition-proof for Class II (Groups E, F & G) when used with conduit. Both models are reverse-wiring protected.

Installation
Mount the pulser target (disc or wrap) to the shaft. Align the ST420 with the arrow label centered on the path of the pulser target magnets. Adjust the gap to 1/4” (6.35mm).

Output Function
The output function is defined by the formula: I(f) = 4mA + 16mA*(f – fmin)/(fmax - fmin). The device operates with a 24V power supply and a 250 Ω load resistance.

Contact Information
Electro-Sensors, Inc., 6111 Blue Circle Drive, Minnetonka, MN 55343. Phone: 952-930-0100, Fax: 952-930-0130. ISO9001:2000 Certified. For assistance, call 1-800-328-6170 or visit www.electro-sensors.com.

Catalog excerpts

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

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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...

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