The FB420 is a shaft speed sensor with relay, built as a self contained system with explosion proof and water resistant housing. The FB420 provides a 4-20mA signal directly proportional to the speed of a monitored shaft and has a 4 digit LCD display capable of displaying from 9 to 9,999 rpm or from 4-20mA. The display of the unit can also be used for calibration and trouble-shooting.

The FB420 has one relay that can be programmed for failsafe over-speed alarms or under-speed alarm. Typical applications include belt conveyors, drag conveyors, bucket elevators, fans, blowers, crushers and pumps.