Electro-Sensors FB420 User Manual

Description:
Electro-Sensor’s FB420 is a shaft speed sensor that provides a
4-20 mA signal that is directly proportional to the rotational
speed of a monitored shaft.
Since both the 4 mA and 20 mA calibration points are
programmable the user can also if desired operate the FB420 with
the 4 mA offset from 0 RPM.
The FB420 has a 4 digit LCD display that is used for calibration
and for trouble-shooting. The LCD is capable of displaying from
‘0.000’ to ‘9999.’ RPM, or from ‘04.00’ to ‘20.00’ mA.
The FB420 has one relay that can be programmed for either
failsafe over/underspeed alarm.
FB420 Installation:
The FB420 needs a rotating target installed on the application’s
drive-shaft, etc. A typical rotating target is a 255 Pulser Disc (with
or without an optional EZ-Mount bracket), or an optional custom-
made Pulser Wrap. (See Figure’s 4a, 4b, and 4c).
0.25 4.40
1.38
2.38
4.00
1.25
2.75
1.63
0.56
Ø0.32
0.26
1.84
4.81
3.90
1“ NPT
Figure 1: FB420 Dimensions w/Bracket and U-Clamp
Figure 2: FB420 Front-View
Electrical connections
The FB420’s electrical connections are as follows:
+24Vdc
Power Supply
(
-
)
(+)
PLC, Etc.
FB420
- +
TB1-2
4-20mA
Shield
TB1-1
TB1-3
250 to 500
ohm load
Ammeter
(optional)
Figure 3:
• Connect any shield wire to the earth ground (if used).
• Connect TB1-1 to the power-supply (+24 Vdc) terminal.
• ConnectTB1-2toaresistiveloadof250Ωto500Ω,(usually
this load is internal to a PLC, etc.).
• Connect TB1-3 to the power-supply (-) terminal.
Note: TB1-2 is the 4-20 mA DC output line.
 Theothersideofthe250Ωto500Ωloadmustbe 
connected to the power-supply (-) terminal.
FB420 Shaft Speed Sensor
6111 Blue Circle Drive
Minnetonka, MN 55343
Phone: 952.930.0100
Fax: 952.930.0130
ISO 9001:2000 Certied
Free Catalog and Application Assistance
1.800.328.6170
Visit Us Online
www.electro-sensors.com
990-003400 Revision C

Electro-Sensors FB420 Specifications

General

Brand	Electro-Sensors
Model	FB420
Category	Accessories
Language	English

Summary

FB420 Shaft Speed Sensor Description

Product Overview

Provides a 4-20 mA signal proportional to rotational speed, with programmable calibration points and an LCD display.

Installation Requirements

Requires a rotating target like a Pulser Disc or Pulser Wrap for operation.

Electrical Connections Overview

Details the wiring for power supply, load, and shield connections for the FB420 sensor.

Pulser Disc and Wrap Installation

Pulser Disc Mounting

Instructions for center drilling, tapping, and attaching the Pulser Disc to the shaft.

Pulser Wrap Mounting

Guidelines for fitting and securing the custom Pulser Wrap onto the shaft.

FB420 Configuration and Operation Modes

Normal Mode Operation

Displays shaft speed in RPM or mA. Relay energizes/de-energizes based on RPM set-point.

Program Mode and Variable Entry

Allows user to change variables (Pr01-Pr06) using increment and enter buttons.

Troubleshooting LCD Messages

Explains meanings and clearing procedures for error codes Err0 through Err4 and 'StOP'.

FB420 General Specifications and Definitions

Input and Output Signal Specifications

Details input power, signal type, operating range, accuracy, resolution, and max signal distance.

Relay Output and Functions

Describes relay type, contact rating, and available functions like Over-speed or Under-speed.

Physical and Environmental Ratings

Covers agency listings, operating temperature, storage temperature, and humidity.

Key Variable Definitions

Explains Pulse Per Rev (Var01), Min RPM (Var02), Max RPM (Var03), and Relay Set-point values.