4-20 mA Loss

What does LFF mean?

This fault occurs when the drive detects a loss of the 4-20 mA analog input signal, which is typically used for speed reference or feedback. This usually means a broken wire, a disconnected sensor, or a faulty analog signal source, causing the drive to lose its command reference and potentially stop or operate incorrectly. It can also be referred to as APL (4-20mA Loss).

Complete Troubleshooting Guide

1. 1

   Check the wiring for the 4-20 mA input for breaks, shorts, or loose connections at both the drive and the signal source.

2. 2

   Verify the 4-20 mA signal source (e.g., sensor, PLC output module) is functional and providing a valid current.

3. 3

   Measure the current directly at the drive's analog input terminals to confirm signal presence and value.

4. 4

   Ensure the analog input configuration in the drive (e.g., input type, minimum/maximum values) matches the connected signal source.