WHAT CAUSES GROUND LOOP AND HOW TO REMOVE THE INTERFERENCE IN CCTV

By: Abdimalik Odowa

Ground loop issues can be caused by different ground potentials between points, for example, between the camera and DVR. These differences are typically cause by unbalanced power line loads or faulty wiring in the electrical circuit where the camera power supply is plugged in.

Experts agreed on most common ground loops are caused by the camera being grounded to a voltage that is different from that of the head-end. If the low-voltage camera is grounded try disconnecting the camera from its ground.

Proper wiring and quality cables are going to be key elements in stopping interference in your camera stream. Two big reasons your cables could be causing video interference issues: the cable itself isn't high-quality enough or the installation of the cable wasn't ideal.

Interference may prevent reception altogether, may cause only a temporary loss of a signal, or may affect the quality of the sound or picture produced by your equipment. The two most common causes of interference are transmitters and electrical equipment.

The easiest way to avoid a ground loop is to connect devices to grounded source and not connect them. The following methods are procedure to eliminate ground loop or minimize the effect of ground loops in your installations

1. DON'T SHARE GROUNDS - The ground wires from a sensor should not be shared with any other sensor or power load. When a ground wire is shared between two sensors, the current from the first sensor will interfere with the signal of the second sensor.

2. MINIMIZE LOOP AREA WITH TWISTED PAIR WIRING - The potential for ground loop interference can be greatly reduced by minimizing the loop area of the conductors between the sensor and the controller. The easiest and most effective way to reduce loop area is with twisted pair wiring which works by cancellation. Each twist acts as a small loop antenna, but after the next twist, the loop is reversed so the interference from the second loop cancels the interference from the first.

3. DON'T GROUND REMOTE SENSORS - If a sensor is placed more than one inch from a controller, only ground the sensor to the ground terminal on the controller which is associated with the analog input you are using (see Figs 3 & 4). Do not ground a remote sensor to building steel or to the power system ground at the remote mounting point. If the sensor’s case must be grounded for safety, isolate the case from the sensor and ground each separately.

4. USE SHIELDED WIRE GROUNDED ONLY TO THE CONTROLLER - In very electrically noisy environments, shielded cable may have to be used. The shield prevents electrical fields from penetrating the wire. The shield should only be grounded at the controller end. If the shield is grounded at both ends, a ground loop will occur.