Electrical Noise - Internal

Electromagnetic interference, or EMI, is a high frequency, low voltage signal on the power lines. EMI is seldom damaging in and of itself. But, like voltage sags, EMI causes damage and loss of product indirectly.

EMI can cause disruption in sensitive devices such as a process control computer regulating gasoline dispensation. The computer may get confused as to how much gas to pump before shutting down, possibly allowing more than what was requested.

Should EMI be a problem, there are three typical solutions, the last one being very complex and expensive.

The first solution is to locate where the interference is coming from and remove or relocate the victim or culprit.

The second is to isolate the victim or culprit by using an EMI filter.

The final solution is very complicated. It is possible that the interference in the power lines began as interference in the air, or what is called radiated EMI. If this is the case, then steps must be taken to identify and locate the source, identify its frequency, and then provide protection to the victim. This protection often takes the form of placing a conductive shield around the device to isolate it from the EMI. Obviously this is complex and costly. Acquiring an EMI consultant is strongly recommended in these cases.