Solutions to the interference of horizontal stripes and stripes in surveillance images

Determine the type of interference first

Ground loop interference (most common)

When the ground potential of the camera and the back-end equipment are inconsistent, a circulating current will form in the shielding layer of the signal line, resulting in 50Hz power frequency interference. Appears as a horizontal bar that slowly scrolls up and down.

Solution:

• Do single-point grounding to avoid multiple-point grounding loops.
• Check whether the camera casing, bracket, pole, and equipment box form multiple grounding points.
• Install a ground loop isolator (video isolation transformer) and the effect will be immediate.
• Use an isolated PoE switch or optocoupler isolation.

Electromagnetic interference

• Keep a distance (≥30cm) between network cables and strong electricity, avoid running parallel cables, and make them vertical when crossing.
• Use shielded network cable (STP), and connect both ends of the shielding layer to ground reliably.
• The metal conduits/bridges are fully connected to the ground.
• Stay away from frequency converters, traction machines, transformers, and high-power motors.
• When the interference is extremely strong, use fiber transmission to fundamentally solve the problem.

Power Interference

• The monitoring equipment has an independent power supply circuit and is not mixed with elevators, air conditioners, and lighting.
• Use high-quality regulated power supplies and adapters to avoid inferior switching power supplies.
• Pay attention to the voltage drop when providing centralized power supply, and the terminal voltage must meet the equipment requirements.
• Install an AC filter or isolation transformer.
• Configure UPS to improve power supply quality.

Troubleshooting steps

1. First confirm whether it is a single channel or all, and narrow down the scope.
2. Move the suspicious camera to the computer room and connect it directly with a short network cable for testing. If it disappears, it is a problem with the on-site line/environment.
3. Disconnect other devices to determine whether they affect each other.
4. Temporarily change the optical fiber or add an isolator to verify whether it is a ground loop or electromagnetic interference.
5. After rectification, continue to observe for 24 to 48 hours before accepting.