How to deal with magnetic interference when installing the LGF-PA66 flow meter next to VFDs and large motors?

VFDs, soft starters and large motors are strong sources of electromagnetic interference. Typical symptoms are unstable flow readings, periodic 50Hz ripple, or flow spikes when nearby equipment starts or stops. For the LGF-PA66, interference is addressed through grounding, shielding and separation distance.

• Grounding: give the sensor its own earth electrode with a grounding resistance of 10Ω or less, never shared with the VFD or the power system. The LGF-PA66 body is made of insulating PA66 composite, which inherently breaks stray currents travelling along the pipe wall — an advantage over metal-bodied meters — but the electrode signal grounding must still be properly implemented.
• Shielding: use the supplied shielded signal cable with the shield grounded at one end only, run it in a separate conduit from power cables, and avoid long parallel runs.
• Distance: keep the transmitter at least 0.5–1 m away from the VFD cabinet; where this is impossible, add isolation barriers on the supply side and on the 4-20mA output loop.

If an EC32 RTU collects data in the same control cabinet, power the RTU through an isolated DC-DC module so VFD harmonics cannot creep into the communication line via the supply and cause Modbus packet loss.

For more information, please visit our product pages or contact our technical team.