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 Certified
Free Catalog and Application Assistance
1.800.328.6170
Visit Us Online
www.electro-sensors.com
990-003400 Revision C
