By: Nissen Isakov
Electromagnetic Interference (EMI) is any degradation of an electrical or electronic device or system caused by an electromagnetic disturbance. Electromagnetic Compatibility (EMC), on the other hand, refers to the ability of such devices to operate properly in their environment without emitting EMI to other devices and, at the same time, be immune to acceptable levels of EMI generated by devices in the same environment.
There are three essential elements to any EMC problem: an EMI source, a receptor device that is victimized by the EMI, and a pathway between the source and the receptor. EMC problems are solved by identifying at least two of these elements and eliminating or attenuating the interference from one of them.
Limiting the level of an EMI source may not eliminate the EMI problem, but may only reduce the potential for an EMI problem. In other words, controlling or regulating levels of interference is statistical in nature and only ensures a probability of non-occurrence of an EMI problem. The management of these emissions and immunity issues as they relate to household appliances is handled very differently in the U.S. than in Europe, even though the statistical procedures for measuring EMI emissions are similar.
The European Union (EU) controls EMC by means of the EMC Directive 89/336/EEC. This EU Directive simply states that all electrical products must be constructed to ensure that any electromagnetic disturbance it generates allows radio and telecommunications equipment and other apparatus to function as intended and the equipment must be constructed with an inherent level of immunity to externally generated electromagnetic disturbances. The focus in the EU is on standards development and standardization, as well as audits and enforcement.
U.S. regulations concerning EMC are enforced by either the Federal Communication Commission (FCC) or the Military. FCC Part 18, states that equipment or appliances designed to generate and use internally generated RF energy for Industrial, Scientific, and Medical (ISM) are subject to these regulations. Therefore, this standard only covers ISM appliances that utilize RF energy to operate, appliances such as induction heaters and microwave ovens.
FCC Part 15 covers telecommunication equipment and digital devices. However, it exempts digital devices utilized exclusively in appliances (e.g. dishwashers, dryers, etc.). Therefore, emissions from computers and other Informational Technology (IT) equipment is regulated, but not the appliances they may be interfacing with. Also, FCC regulations only apply to EMI and do not include any immunity or susceptibility standards. So currently, appliances in the U.S. do not need to meet any EMC compliance standards.
Since U.S. appliance manufacturers essentially can (and do) produce domestically used products without any regard for EMI suppression, how serious is the EMC problem in the U.S.?
It’s difficult to know the entire scope of the problem, but a few examples have come to our attention. For example, the new 2.4GHz portable phones will not function in or near laundry rooms when certain models of washing machines are running. This problem is easily overcome by not using the portable near these washers. A little inconvenient, but not intolerable.
In another case, a company that imports and distributes microwave ovens asked us to investigate complaints that some of their microwave ovens were turning on by themselves. Obviously, an unintentionally activated microwave oven is more serious than not being able to use a portable phone in the laundry room. The cause was a surge on the power line, probably caused by the air conditioning system turning on. The solution was not simple and required units to be recalled and fitted with a hardware and software modification. The costly remedy was necessary because, in this case, the susceptibility of the appliance electronics created a safety hazard.
In recent years, appliance manufacturers have been promising us new age smart homes where networked appliances provide communication and control features designed to deliver more convenience, energy efficiency and interactive options such as remote diagnostics and the ability to download upgraded control programs.
However, the means by which these opportunities may be implemented may also introduce new opportunities for EMI problems in that these networked appliances must be able to send and receive communication signals. There are different networking technologies being considered— dedicated wiring, phone line, powerline, radio frequency—and within each of those options are more choices regarding protocols, hardware and software. OEMs will face other decisions, as well. Will the network be strictly internal within the home, or externally linked via the Internet? Will an OEM’s appliances communicate only with other appliances of the same brand, or will they offer the potential to be linked to other brands and systems?
Each decision will present its own unique array of EMC issues to ensure that these smart appliances operate how and when they are supposed to. Inter-appliance EMC problems may not be evident initially, but as the use of these appliances become more prolific, the potential for erroneous operation and customer dissatisfaction will become more pronounced.
As stated previously, EMI issues are defined in terms of statistical probabilities, and the probability of having EMI problems increases exponentially as electronic devices in the home become more abundant and closer together. The ability of EMI to interact with susceptible systems that are exchanging electronic data also has the potential of causing serious safety hazards. So while EMI in the present environment may be merely inconvenient, electromagnetic incompatibility in smart appliances of the future may very well be intolerable.
In Europe, EMC issues will continue to be managed through the existing EMC Directive, so European appliance manufacturers will remain quite familiar with designing and developing next-generation products that are EMC compliant.
Without such a directive here, U.S. appliance manufacturers will need to institute good EMC practices and measures to ensure a more EMC friendly environment for smart, networked appliances. Electronic control engineers will need to design EMC compliant appliance controllers. And consumers may have to pay a little more for appliances to ensure that they are manufactured to higher EMC standards. That’s because, unfortunately, what is normally good practice for electronic circuit design, is not necessarily good practice for EMC design. But the added cost of EMC compliance will be well worth it if it can prevent smart homes from turning into chaotic homes.