Motion & Slowdown Monitoring Systems


The FB420 provides a 4-20 mA signal directly proportional to the rotational speed of a monitored shaft and has a 4 digit LCD display capable of displaying from 0.000 to 9,999 rpm or from 4 to 20 mA, the display is also used for calibration and trouble-shooting. The FB420 has one relay that can be programmed for failsafe over-speed alarm or failsafe under-speed alarm. Typical applications include belt conveyors, drag conveyors, bucket elevators, fans, blowers, crushers, and pumps.


  • Self-contained system with sensor and switch
  • Relay can be set for over-speed or under-speed
  • Housing is explosion proof and water resistant
  • 4-20 mA output directly proportional to shaft speed
  • Provides real-time preventive maintenance feedback
  • Class I, Div I (C, D) Class II (E, F, G)


Speed Switch

The M800 Elite Speed Switch is designed to detect belt slip, belt underspeed, stop motion, low speed or zero speed on bucket elevators, conveyors, airlocks, mixers, fans, grinders and many other rotating machines.  Totally sealed and simple to calibrate, the M800 Elite works in the harshest of conditions.
M800 Elite Speed Switch
An inductive sensing device located in the nose of the M800 Elite enclosure will detect a metal target.  This target can be an existing bolt head or device attached to a shaft.  During installation the M800 Elite is set to the normal machine shaft RPM by calibrating with the magnet provided.  The internal microprocessor sets the alarm and shutdown relays.  Two M800 Elite models are available:

Model M8001V10C (standard version) may be used either as a dual trip unit with an alarm at 10% below set speed and a shutdown signal at 20% below set speed, or a single trip giving a shutdown signal at 20%. 

Model M8002V10C may be used either as a dual trip unit with an alarm at 5% below set speed and a shutdown signal at 10% below set speed, or a single trip giving a shutdown signal at 10%. 

A simple calibration facility allows either model to be programmed to give a start up delay of up to 15 seconds, while simultaneously calibrating for normal running speed.  If required, the M800 Elite has an additional pulsed output, which can be connected to display actual shaft RPM on a PLC or speed display.


  • Microprocessor Controlled
  • LED Indicator
  • Non Contacting and Fail-Safe
  • Totally Sealed Construction
  • Dual Set Points for Alarms and Shutdowns
  • Universal Voltage (24-240 VAC/VDC)

Whirligig M300 Slipswitch


The Whirligig® is a fully guarded target for easy mounting of motion sensors. It is a universal shaft sensor mount suitable for all industry standards cylindrical or DIN style inductive sensors including 4B's M100, M300, and M800 speed switch sensors.
The sensor bolts to the Whirligig base plate and the complete assembly either bolts to the machines shaft through a 1/2 in. UNC tapped hole, or is connected magnetically using 4B’s patented Mag-Con™ adaptor. Shaft or machine vibration does not affect the performance of the sensor, as the whole assembly moves with the shaft. With the Whirligig, installation of speed sensors is now simple, safe and reliable.


  • Fully Guarded Target for Easy Mounting of Motion Sensors
  • For DIN Style and Standard Cylindrical Inductive Sensors
  • Easy Installation- Only Requires ½” UNC Tapped Hole in Machines
  • Shaft or Use Mag-Con for Magnetic Connection
  • Available in 1, 2, 4, or 8 Targets
  • Works with all 4B Speed Switches and Inductive Sensors






Mag-Con™ Magnetic ConnectorMag-Con™ Magnetic Connector

The Mag-Con™ (MAG2000) is an optional magnetic connector that screws onto the Whirligig and magnetically couples it to the shaft being monitored. The Mag-Con is made from stainless steel, has a holding force of over 150 lbs. and can withstand speeds up to 300 RPM.