Beta Solutions Blog

Author: Jason Cleland, Electro-mechanical Engineer

So you've got an idea for a brilliant new product that you want to develop and then put to market? And you've heard about this thing called 'EMC' but you don't know exactly what it is or why it should matter to you? Or how long will it take? Or how much will it cost? The purpose of this blog is to answer some of these questions and explain what 'EMC' is and why you really do need to know about it.

If you haven't already, please read our previous blog on compliance, Electronic Product Compliance - Answers to FAQs, which answers common questions our customers have had about complying with the regulations which govern electronic products here in NZ and abroad.

What is 'EMC'?

EMC or Electromagnetic Compatibility is a term which refers to how well electronic devices operate within the same vicinity without interfering with each other. A device which has poor Electromagnetic Compatibility could either cause problems with nearby devices or those same devices could cause it to have problems. You may have experienced this yourself if you ever used an older wireless home phone at the same time that a microwave oven is operating. The electromagnetic energy being emitted from a 'leaky' microwave oven can be detrimental to the audio quality on those old handsets. Wifi performance can also be slowed down or interrupted by 'leaky' microwave ovens or other wireless products like baby monitors or security cameras.

Almost all electronics emit at least some electromagnetic energy during their operation. This is just a consequence of using electrical energy. Given a high enough magnitude, almost all electronics can be susceptible to the energy being radiated from the devices around them. Due to this inherent relationship between devices, it is imperative that designers consider EMC during the development process else risk poor compatibility with the environments that their product operates in.

The result of unintended interactions between devices can range from imperceptible to disastrous. An interrupted phone discussion is a minor annoyance but a passenger aircraft navigation system is critical and the potential result of poor EMC design could be injury or death. In today's modern world there are electronics everywhere which all emit invisible electromagnetic energy. It's only through good design and testing that this has been achieved with few unintended interactions.

Radio Spectrum Management (RSM) is the governing body which regulates EMC products in New Zealand.

Why should you concern yourself with EMC?

In short, because it is a legal requirement ^[1].

All markets have laws and regulations which govern how electronic products interact with the environments around them. There are often tests which are mandated by these regulations which have to be done before the device can be sold in that market. There are 'Standards' documents which define all the tests a device must pass in order to prove compliance with the regulations ^[2]. Devices which fail any of these tests would then be disallowed from being sold in that market until it is modified or fixed so that it passes the tests. 

You could have both an amazing product and customers lined up but if you can't prove it's compliant with the EMC regulations of that market, you won't be able to sell a single unit ^[3]. Concerning yourself with EMC during the development process reduces risk and the liability of a product with poor EMC.

What is EMC testing?

To prove that your device is compliant you must have documentation which shows that the device has passed all the tests specified for that product category ^[4]. This documentation usually comes in the form of test reports produced by an independent test laboratory. These test laboratories are accredited by a governing body so that the test reports they produce can be recognised as proof of compliance.

There are two main categories of testing which can be done to measure the electromagnetic compatibility of a device. The most commonly required category is 'Emissions' testing which measures how much energy the device radiates or conducts out and compares this to set limits. The other main category of EMC testing is 'Immunity' testing where the device is put in prescribed electromagnetic environmental conditions to test it's susceptibility to electromagnetic phenomena it may experience in the real world.

Emissions Testing

Emissions testing typically measures how much energy the device emits with the following modes:

• Radiated Radio-frequency (RF) Fields - Radiated RF fields are electromagnetic disturbances caused by the electrical activity in a device, and radiated out through the air.
• Conducted RF Noise - Conducted RF emissions are also electromagnetic disturbances caused by the electrical activity, but are conducted out along its cables.
• Magnetic or Electric Fields - Electrical activity in a device can produce magnetic or electric fields which can have near-field effects. Fluctuating voltages or currents in one device can induce or couple unwanted voltages or currents in other nearby devices.

The image below ^[5] shows various RF antennas used to measure the radiated RF fields of an electronic device: