What is EMC Testing?
Electromagnetic compatibility testing, commonly known as EMC Testing, is compulsory for manufacturers of certain products in the UK. This testing is necessary to demonstrate that their products are compliant with EMC standards, and is essential to meet the mandated requirements for distribution to the market. Most of today’s electrical products and electronic equipment are subjected to electromagnetic compatibility testing.
The Importance of EMC Testing
EMC testing is mandatory for almost all products which have an electronic or electrical circuitry whether wired or wireless powered. This is to ensure that products can function satisfactorily in the environment which they are going to be used. Furthermore, so they do not cause interference to other products.
Product testing is found to be highly beneficial for manufacturers, especially during the development cycle. Catching issues early on in this cycle can highlight failures earlier, and help to avoid costly product recalls and associated delays. A test failure identified at the end of the product development process can prove extremely costly, especially in redesign of the product.
What Types of Equipment & Markets Require EMC Testing?
Compliance with the EMC testing is mandatory in almost all markets including the U.S., Europe and Australia, among many others. This test is required for manufacturers in various industries including, but not limited to:
- Medical devices;
- Consumer products;
- Military equipment;
- Industrial machinery;
- Aerospace; and
What Kind of Equipment Needs to be EMC Tested?
In general, if your product contains any active electronic components, (such as diodes, transistors, microcontrollers, etc), then your product is required to be tested under the EMC Regulations. There are a few exemptions such as the following:
- Custom-built evaluation equipment – This applies to kit that has been built for a single customer by request, for use in research or development. If the kit is later provided on a regular basis, or goes on to be used for purposes other than research or development, then it can no longer be considered exempt from the regulations.
- Evaluation kits – Electronic evaluation kits as supplied from many electronics manufacturers are exempt from the regulations as they are intended for use by professionals for research & development purposes.
An exemption cannot be claimed for any equipment that is to be used on a regular basis, such as laboratory equipment, equipment used to perform tests for the purposes of research or for other applications such as demonstrating the conformity or quality of a product.
Inherently Benign Equipment
There is another exemption from the regulations for equipment that is electromagnetically benign as a result of the design & construction.
Equipment can be considered benign for purposes of the regulations if the inherent characteristics are such:
- The device is incapable of generating or contributing to electromagnetic emissions which exceed a level allowing radio and telecommunications equipment and other equipment to operate as intended; and
- The device will operate without unacceptable degradation in the presence of the electromagnetic disturbances normally encountered in its intended environment.
The product has to meet both of these conditions to be considered benign. Examples of equipment that would be covered under this exemption are:
- Cables, or cable assemblies, separate from any product. (Manufacturers should consider the potential significant effect on EMC performance of equipment when cables are installed).
- Equipment containing only resistive loads without any form of automated switching devices; such as heaters, kettles, fans.
- Batteries without any active electronic controls.
- Corded passive headphones, unamplified loudspeakers, and guitar inductive pickup coils without electronic controls.
- AC induction motors without electronic speed controls or Variable Frequency Drives.
- Pocket lamps without active electronic circuits (including LED lamps).
- Quartz watches without any additional functions other than timekeeping.
- Mechanical Switches.
- Passive Antennas.
- Electromechanical relays without active electronic parts.
Preparation for EMC Testing
It’s imperative for manufacturers to prepare the EMC testing requirements prior to entering the EMC test chamber in order to achieve the best results.
To be able to avoid delays in the marketing of your products, you need to properly prepare for what is needed prior to the final EMC testing. You must also allocate enough time to book an available booking at the testing laboratory, sometimes the lead time can be weeks. You must also allow a contingency plan if the product initially does not comply. Allow time for any re-work or modifications are required i.e. compliance engineering the product to meet the standards.
Prepare a Test Plan
Before the testing is done, it is necessary to be able to define the process beforehand. Analysing the requirements and knowing the types of test that your product needs to undergo is imperative. You need to know whether your product is subjected to conducted and radiated emissions only. Or if you will also need the EMC immunity testing as well. You will also need to know which ports will be tested, which levels or limits will be used and what the pass and fail criteria are. That is why writing a test plan is essential.
What Information Should be On My Test Plan?
If you have already undergone Electromagnetic Compatibility Testing before, then you will be able to create a test plan yourself. However, if it is your first time to have an EMC test conducted, you might need a little bit of assistance. A good test plan must have the following:
- Product name, model number and identification details;
- Product description of device to be tested including its I/O configurations and peripherals;
- Required standards and applicable tests that is listed in the standards;
- Quantity of samples requiring testing;
- Product power supply requirements, i.e. 115/230VAC, 50/60Hz, 12VDC, PoE etc;
- Dimensions of the product/system and also the weight of the product/system;
- Type of equipment is it tabletop or floor standing;
- Transmitter information if an wireless radio module is incorporated or used;
- The lowest and highest internal frequencies used within the product;
- Ports table including cable types, quantities, terminations and cable lengths;
- Operating modes of the product;
- Operating mode of the product and configuration for emissions testing (worst case);
- Product emissions limits i.e. Class A, Class B etc (if applicable);
- Operating mode of the product and configuration for immunity testing (worst case);
- Declaring the intended environment, such as Basic, Industrial or Controlled EM etc;
- EUT cycle time to complete all operations and allow observation of any failures;
- Customer specified performance criteria and ways to recognise, monitor and report failures;
- Test fixtures, special software and supporting equipment to correctly exercise the product;
- Definition of failure;
- Estimated set-up time of the physical configuration and support equipment/software;
- Declaring any health and safety related issues such as hazardous materials etc;
- Special needs such as power, software and cooling among others;
Getting Testing Scheduled
Once you have the test plan written, you can now get the pricing and scheduling from an accredited 3rd party EMC test lab such as ourselves. Prepare the software and hardware for testing. More often than not, you will need the following:
- Equipment under test (EUT) and spares;
- Test fixture (if required);
- Auxiliary support equipment;
- Connectors and cables;
- Equipment’s design documentation
During the test, it is often handy to have an engineer who knows the equipment present to assist the test engineers in operation & monitoring of the product for any potential failures as they occur.
Preparation Prior to Testing
Additionally, possible delays can be avoided if you are well prepared for the testing. Hence, when preparing your software and hardware for testing, you need to take note of the following:
- The product that has to be tested must have its peripheral equipment included which constitute the entire system;
- Any optional or auxiliary equipment that may be required during the test. If your product has a USB port, include a USB peripheral that can be used for that port. If you don’t ship a product with USB peripheral, then you provide a typical unit. Ensure that unit is pre-compliant to avoid failure during the test;
- If functional auxiliary equipment for a particular port is not possible, dummy loads that exercise a port to its fullest extent will often do;
- A monitoring method. This is crucial for immunity testing since the lab needs to monitor the performance of your product. Clearly defining methods for which you would like your product to be monitored is helpful to EMC test labs;
- Two or more alternative backup power supply units. This is helpful whenever there’s a failure in conducted emissions testing. Conducted emissions problems can often be alleviated by swapping an external power adapter with a better performing one. Having more adapters can also be useful when doing surge testing;
- Cables that are needed when exercising your product to the fullest. They must be the right length.
- A software/firmware test mode that is needed when exercising all communication interfaces, memory interfaces and all moving parts at the highest speed possible; and
- Proper documentation needed by the test engineers. This is highly important because if test engineers don’t know how to set up or operate your product into the proper test mode, it could delay the test schedule.