Difference Between Panel Earthing and Instrument Earthing

What is Panel Earthing?

Panel Earthing refers to connecting the metallic body, frame, and internal grounding busbar of an electrical or automation control panel to the earth. It ensures that any fault current, leakage current, or internal insulation failure safely flows to the ground instead of through equipment or people.

Purpose of Panel Earthing

Protects human operators from electric shock
Prevents panel body from becoming energized
Provides a safe path for fault current
Reduces risk of fire due to leakage current
Improves overall electrical system safety

Where Panel Earthing is Applied

MCC panels
PCC panels
PLC/SCADA control panels
VFD/soft-starter panels
Distribution boxes and junction boxes

What is Instrument Earthing?

Instrument Earthing is a dedicated grounding system used specifically for control and instrumentation circuits. It provides a clean, noise-free ground reference to sensitive electronic devices like transmitters, PLC I/O, sensors, analyzers, and communication systems.

Instrument earthing is kept separate from power earthing to avoid electrical noise, harmonics, and voltage spikes entering the measurement circuits.

Purpose of Instrument Earthing

Provides stable reference for 4–20 mA and 0–10 V signals
Prevents signal noise and fluctuations
Protects PLC, DCS, SCADA, and I/O modules
Prevents ground loops in communication
Improves accuracy of instruments and sensors

Where Instrument Earthing is Applied

Transmitters (PT, LT, FT, TT)
RTD, thermocouples, temperature converters
PLC I/O cards
Analyzers (pH, DO, conductivity)
Communication networks (RS485, Profibus, Ethernet)