Electromagnetic interference (EMI) is an unavoidable fact of physics. When current moves through a conductor, an electromagnetic field is created, and this field can interfere with other electronics nearby. In order for devices to function as designed, they must be protected from both emitting and being susceptible to EMI. The task of making all the world's electronic devices work in harmony by limiting EMI is known as electromagnetic compatibility, or EMC.
Today we take a dive into EMC and examine the Australian standards that govern its application, how companies can manage their obligations under the law and how Interconnect's range of products can help in this task.
What is electromagnetic interference?
Electronics come in a variety of forms with a variety of functions. Some are powerful transmitters of signals, others are sensitive receivers and others still do neither but, crucially, all three kinds can create havoc for other electronics through their operation. As such, it's important electronics are designed with EMC in mind, otherwise many products would struggle to function as they should.
It's easy enough to forget that there was once a time when electronics were rare in society. As such, most people were unaware of the interference patterns that electronics can generate — crackles and pops on the radio were once thought of as inevitable by-products of the technology, rather than being caused by electromagnetic interference from other devices nearby. This discovery of the interference electronics could create led to the increased focus on engineering products with EMC considerations in mind.
EMI makes its presence known in a number of ways. It can cause communications links to falter, diminish the ability of sensitive equipment to accurately measure things, or just limit the ability of a device to function as it should. There are two ways EMI can interfere with electronics:
- Continuous interference — a constant, unchanging pattern, like a radio signal.
- Impulse interference — a burst of interference that's non-continuous, like a circuit being switched on.
It's important to note that EMI doesn't only come from man-made electronics; things like lightning strikes or solar flares can create EMI and impede the function of electronics too.
What is electromagnetic compatibility?
Because of the ubiquitous nature of electronics today, standards for managing the interference problems that could result are needed. Electronic devices need to be able to work with and around other electronics and this is the task of EMC.
There are two factors that need to be controlled in pursuit of EMC:
Electronics create electromagnetic emissions that can affect other pieces of equipment. These emissions have to be controlled and limited below certain levels, which are dependant on the device in question.
Even though best efforts are made to minimise electromagnetic emissions, there may still often be unwanted signals in the operating environment of electronic equipment. For this reason, EMC also aims to engineer circuit designs that are as immune as possible to unwanted interference.
In both cases, physical shielding using materials that can reflect or absorb the unwanted energy is often used. This presents interesting engineering problems, because EMC requirements are not the only ideals products are designed in line with; real world functionality means there often has to be openings, cabling and heat management considerations that require more inventive shielding solutions that simply enclosing a circuit inside a steel casing. A common example is woven metal sleeves that encase cabling in a protective shield while retaining much of the flexibility that cables generally have.
What are the Australian EMC standards?
In order for EMC to be possible, every designer and manufacturer of electronics needs to be working to the same standards of emission control and susceptibility minimisation. For that reason, EMC standards are enshrined in law, with the Australian Communications and Media Authority (ACMA) the responsible party for setting EMC standards in Australia. All electrical equipment must comply with the standard relevant to that kind of equipment.
The standards outline the labelling and record keeping requirements for certain kinds of equipment. Devices are split into three levels that correspond to the risk of that product emitting unwanted electromagnetic signals; high-risk equipment that's non-compliant is more likely to cause interference, and therefore requires more stringent testing and greater evidence of compliance than do low-risk devices.
The ACMA explain the levels as follows:
Compliance Level 1/low-risk device
These are devices like battery-powered calculators, torches, or watches — basically any small battery powered electronic device. A battery-powered device for the purposes of EMC standards refers to something that can't be plugged into an external power supply.
Low-risk devices have to comply with the relevant standard, but the evidence used to prove compliance can be chosen by the manufacturer. There is also no obligation to label or maintain a Declaration of Conformity (DoC), but if the former is pursued the latter must be created.
Compliance Level 2/medium-risk device
Medium-risk devices are anything that's not a high-risk device and contain at least one of the following components:
- a switch mode power supply.
- a transistor switching circuit.
- a microprocessor.
- a commutator.
- a slip-ring motor.
- an electronic device operating in a switching or on-linear mode.
These are things like TVs, laptops, printers, video-game consoles and electronic ballasts. Suppliers of medium-risk devices are required to label their equipment and keep the following forms of evidence:
- A test report or test construction file that shows the device complies with the relevant standard.
- A declaration of conformity.
- A description of the device.
Compliance Level 3/high-risk device
High-risk devices are ISM equipment where radio-frequency energy or electromagnetic radiation is created on purpose for a specific purpose. These are products like induction heating equipment, microwave ovens, arc and spot welding equipment, and induction cookers.
In terms of labelling and evidentiary requirements, high-risk devices face the same criteria as medium-risk devices. The only difference is the testing they're subject to for labelling must be done by an accredited testing body.
How can I make sure my product is compliant with EMC standards?
While the exact procedure may vary with the product in question, in general, complying with EMC regulation involves the following steps:
1) Identify the equipment type and the relevant standard.
2) Have the equipment tested for compliance with that standard.
High-risk devices must be tested by an accredited body.
3) Complete a Declaration of Conformity attesting to the products compliance with the standard.
4) Register the product and apply any necessary labels
Manufacturers of low-risk devices can choose whether or not they want to apply a label, but they are still responsible for making sure their device complies with the relevant standard.
If you follow those steps, you should have all your bases covered when it comes to EMC compliance. If you're not sure you've done all you need to, you can get in touch with a testing body, and they can run you through everything you'll need to do.
Interconnect's role in managing EMI
You might be wondering what role Interconnect plays in this world of EMC; the answer is, we have many.
For a start, we manufacture backshells, the pieces of industrial connectors that form the back end, protecting them from EMI. Backshells provide effective defence from EMI, halting its influence in one of the common places unwanted energy can 'leak.'
Another of our products that can make managing EMI easier is fibre-optic cables. Unlike their copper counterparts, fibre-optic cables are resistant to EMI, making them a perfect part of a system designed to resist malicious electromagnetic-pulse weapons.
Finally we stock a number of products designed to screen and protect cables and other components from contaminants, including unwanted EMI.
The Interconnect team is experienced in helping the innovative companies we work with manage their EMC compliance. To learn more about us, our product offerings, and how we can help you and your business, get in touch with us today.