Short Answer:

Shielding helps in reducing electrical noise by blocking unwanted electromagnetic or radio frequency signals from entering sensitive measurement or communication circuits. It works by surrounding cables, devices, or enclosures with a conductive material that absorbs or reflects the noise before it can interfere with the signal.

By creating a protective barrier, shielding prevents external noise from affecting internal signals and also stops internal noise from radiating out. It is a simple but very effective technique used in cables, enclosures, and electronic devices to improve signal quality and system reliability.

Detailed Explanation:

Shielding in reducing noise

In electrical and electronic systems, especially in measurement and communication circuits, electrical noise can severely affect performance and signal accuracy. This noise may come from nearby electronic devices, power lines, radio waves, or even other parts of the same circuit. Shielding is a common and effective method used to reduce or eliminate noise interference by enclosing the components or signal paths in conductive materials.

The main idea is to block or redirect unwanted electromagnetic energy away from the sensitive parts of the system, ensuring clean and stable signal transmission.

How shielding works:

Shielding uses materials like copper, aluminum, or conductive mesh to form a barrier around cables, devices, or components. This barrier can:

1. Reflect external electromagnetic fields so they don’t reach the inner circuit.
2. Absorb and safely redirect noise energy to the ground, preventing it from entering the signal path.

This is achieved by connecting the shielding layer to electrical ground, which acts as a safe path for the unwanted signals to drain out.

Common shielding applications:

1. Shielded Cables:
   • In cables carrying sensitive analog or digital signals, shielding surrounds the inner conductor.
   • It blocks interference from nearby wires, motors, or power lines.
   • Common types include coaxial cables and shielded twisted pairs.
2. Electronic Enclosures:
   • Devices like sensors, amplifiers, and control units are often placed inside metallic cases to protect against external noise.
   • These cases act as a Faraday cage, blocking radio frequency and electromagnetic interference.
3. Printed Circuit Boards (PCBs):
   • Ground planes and shielded layers are used in PCBs to separate noisy and sensitive areas.
   • Shielding cans may be placed over critical components.
4. Medical and Test Equipment:
   • High-precision instruments often use shielding to eliminate external noise and ensure accurate readings.
   • Examples include ECG machines, oscilloscopes, and digital voltmeters.

Benefits of shielding:

• Reduces electromagnetic interference (EMI)
• Improves signal integrity and accuracy
• Protects sensitive equipment from external disturbances
• Prevents signal loss and distortion in long cables
• Ensures compliance with safety and EMI standards

Things to remember:

• Shielding must be properly grounded to be effective.
• Breaks or gaps in shielding can allow noise to enter.
• Over-shielding may add cost and weight, so it should be used only where necessary.
• Combination with other techniques like filtering and grounding gives better results.

Conclusion:

Shielding reduces noise by blocking or diverting unwanted electromagnetic signals away from sensitive circuits. By surrounding signal paths or devices with conductive materials connected to ground, shielding provides a protective layer that ensures cleaner, more accurate signal transmission. It is an essential tool in building reliable and noise-free electrical systems.