Diverts surge current to earth while limiting transient voltage on the protected signal circuit.
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Product Overview
PEPPERL+FUCHS FS-LB-I is a one-channel field-mount surge protection barrier for signal lines.
It uses an M20 × 1.5 mounting thread, a polished AISI 316 stainless-steel housing and a 0.3 m cable for direct installation at a field device.
The barrier is rated for circuits up to 48 V and 250 mA, with 500 V isolation from earth and a 20 kA total discharge-current rating for an 8/20 µs impulse.
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Performance
Maintains less than 5 µA leakage at the rated circuit conditions.
Provides a symmetrical response time of 1 ns and asymmetric response of 100 ns.
Supports signal bandwidth of at least 40 kHz.
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Technical Details
Manufacturer
Pepperl+Fuchs
Exact model
FS-LB-I
Protected lines
1
Mounting thread
M20 × 1.5
Rated voltage
48 V maximum
Rated current
250 mA maximum
Leakage current
5 µA maximum
Ground insulation
500 V minimum breakdown voltage
Total discharge current
20 kA at 8/20 µs
Housing
AISI 316 stainless steel
Degree of protection
IP67
Ambient temperature
−30 to +60 °C
Cable length
0.3 m
Dimensions
22 mm across flats × 77 mm
Functional safety
Up to SIL 3
About IndustryParts
https://www.industryparts.com/Thread, loop limits and earth path are checked together
IndustryParts prepares PEPPERL+FUCHS FS-LB-I enquiries around the exact M20 execution and the protected circuit evidence.
M20 thread confirmed
Loop limits recorded
Earth route reviewed
04
System Integration
Install PEPPERL+FUCHS FS-LB-I in the free M20 cable entry of the field device.
Bond the green/yellow earth conductor using the approved low-impedance route.
Confirm the protected circuit does not exceed the published 48 V and 250 mA limits.
Apply the hazardous-area certificate, conductor segregation and enclosure requirements for the installation.
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Applications
Protection of transmitter and sensor signal wiring close to the field device.
Hazardous-area instrumentation exposed to lightning-induced or switching surges.
Two-wire isolated control and instrumentation circuits requiring field-end protection.
Retrofit protection where the M20 entry and earthing path match the approved installation.
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FAQ
Q01Why is the earth path critical for PEPPERL+FUCHS FS-LB-I?
The unit protects by diverting surge energy to earth; a long or high-impedance bond reduces that path’s effectiveness.
Q02Can PEPPERL+FUCHS FS-LB-I be fitted to a ½ NPT entry?
No. FS-LB-I is the M20 × 1.5 version; the FN-LB-I family is associated with the ½ NPT thread.
Q03Which circuit data should be checked before selecting PEPPERL+FUCHS FS-LB-I?
Confirm normal voltage and current, intrinsic-safety parameters, signal bandwidth, cable entry, earthing and hazardous-area approval.
Q04Does PEPPERL+FUCHS FS-LB-I require replacement after every disturbance?
Inspect and test it after a known surge event; replacement decisions must follow the device instructions and plant maintenance procedure.
Q05What should accompany a PEPPERL+FUCHS FS-LB-I enquiry?
Provide field-device model, M20 entry, loop voltage/current, hazardous-area classification, earthing arrangement, quantity and destination.
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