Do you believe in electrical ghosts? Understanding electrical noise

I have found that many people, even in the industrial automation field, do not seem to believe in or recognize electrical noise. This lack of knowledge I witnessed over the course of 25 years has always been something that interested me. Why is it that so many in the industry seem to have a disconnect with the concept of electrical noise? Although at a certain point, the “why” was just as important as the education. I have many years of experience combating this often-overlooked issue and have gravitated toward certain effective methods.

Electrical installations are the backbone of any industrial system. A well-executed installation can prevent numerous issues, while poor ones can introduce problems that are difficult to diagnose and fix. In fact, electrical noise is not just an industrial issue. It is something many consumers encounter at home and aren’t even aware of it:

Wi-Fi dropouts: Have you noticed your Wi-Fi cutting out when the microwave is on? This could be due to the electromagnetic interference (EMI) generated by the microwave, disrupting the Wi-Fi signal.
Buzzing speakers: Ever heard a buzzing noise from speakers when a cell phone is nearby? This is another example of EMI, where the phone’s signal interferes with the audio equipment.

These everyday examples highlight the pervasive nature of electrical noise and the importance of proper shielding and grounding in both home and industrial settings.

Symptoms on machines

In industrial environments, symptoms of electrical noise can manifest in various intermittent ways. For instance:

Sensors can have sudden and unexplained readings such as momentary triggers or spikes.
Feedback devices may provide inconsistent or inaccurate readings.
Motion problems such as jittering or drifting of servo motors.
Communication problems with interruptions in data transmission, even over ethernet.
Static electricity builds up over time and then releases all at once, zapping components. This is typical in machines unrolling large rolls of plastic.
Randomly failing components suddenly failing after some time, seemingly for no reason, such as serial ports blowing up or internal capacitors failing months after units were installed.

EMC installation instructions: Critical yet ignored

Electromagnetic compatibility (EMC) guidelines are essential for minimizing electrical noise, yet they are often overlooked. Once the principles of EMC are understood, the importance of these instructions becomes clear. Adhering to EMC guidelines ensures smooth and reliable operation of industrial systems. Unfortunately, many of these guidelines are in fine print or referenced in a drawing that few people can decipher.

After my time at one motion control manufacturer learning these concepts, I started working with other manufacturers. I didn’t hear them talking about these concepts and problems which made me initially think that this topic was somehow specific to the manufacturer that I had worked for. But, as I asked more questions of other manufacturers and dove into their EMC installation guidelines, I found out that they, too, had noise issues and also gave the same directions in their guidelines. However, the details were so fine and subtle in their guidelines that they were very easy to miss.

EMI filters

EMI filters, also known as mains filters, are crucial in managing electrical noise, and there are three primary reasons for using them.

First, EMI filters are vital in preventing external noise from entering your system. This protection is essential for maintaining the integrity and performance of your equipment. Without these filters, external noise sources, such as welders and huge AC motors, can cause significant disruptions and degrade system performance.

Second, containing internally generated noise is equally important. EMI filters help ensure that noise created within the system by servo drives and other power-switching products does not interfere with other equipment. This containment is critical for maintaining a clean operational environment, especially in facilities with multiple electronic systems operating simultaneously.

If you cannot stop it, direct it! EMI filters provide a controlled path for electrical noise in order to prevent it from causing interference or damage. This aspect is often overlooked but is crucial for effective noise management. By controlling the path of the electric noise, one can direct the noise away from sensitive components within the system and help to maintain the system’s reliability and longevity.

Evaluating the electrical installation?

Assessing the quality of electrical installations is crucial for preventing noise issues. There are several different approaches to evaluating your setup.

The shotgun approach involves a basic performance check to see if the system operates adequately. While not precise, it can serve as an initial assessment to identify obvious issues. The problem with this approach is that intermittent and very frustrating performance problems can occur that few people will recognize as being caused by electric noise.

Using tools such as multi-meters and oscilloscopes for spot-checking provides a more detailed understanding of your system’s electrical integrity. This method allows for the identification of specific problem areas that may not be apparent through basic performance checks.

The multi-meter approach can be used to measure voltage differences between ground points and other critical areas. An oscilloscope can measure and visualize electrical noise on power lines and grounding points, providing a clearer picture of noise levels.

Real measurements

For a comprehensive evaluation, consulting services for CE certification and thorough testing offer the most accurate assessment of your installation’s performance. These services, while costly, can provide detailed reports and recommendations for improving your system’s electrical performance and therefore CE (EMC) compliance.

Electrical noise can be a tricky subject to address. Understanding the why and being able to recognize the symptoms are a great start. Then, once one can recognize the issue, strategies for management and more importantly, prevention can be addressed. It never hurts to consult with someone with ample experience in the field.

Valin Corporation