Having already discussed about Pre – Compliance Testing, in this post we will discuss about 3 out of 5 of the pre-compliance options available for radiated emission testing.
- Design Review: This is one of the most overlooked pre-compliance method. Design review isn’t really a pre-compliance testing method but it does the same thing. It is designed to reduce the risk of the failure of the product in an EMC Test. There are numerous textbooks that can provided with the needed guidance. This method increases your chances of passing the test in one go because you can identify so many emission and immunity problems in a design review.
- In-House Semi-Anechoic Chamber (SAC): This option is suitable for companies that work on a large scale. The companies that design a number of products per year and have abundance of financial resources should avail this option. This method usually gives results quite close to that what a test lab would measure. To avail this method of pre-compliance testing certain equipment is required. This includes a chamber, antennas, spectrum receiver or analyzer, and a turntable. You can also find used chambers but it is important to note that the effectiveness of the chamber reduces over time. The material lining the chamber which is used for absorbing the radio frequency energy and restrict it from bouncing off the walls degrades. As the material degrades, the reflections increase and then the measurements are not that reliable.
- In-House Open Area Test Sites (OATS): OATS is used by many accredited test labs for the final measurements while testing the products. As there are no walls, the signal received at the antenna is a combination of the signal that has bounced off the metallic ground plane and the signal received directly from the equipment under test. One of the major problems of this option is that it is hard to identify the emissions coming off the product because you are not immune to the ambient radiations. You are going to experience unwanted signals like those from cell phone bands, FM stations etc. An ideal OATS is built according to ANSI C63.7 and C63.4 standards or/and CISPR 16-1-4 standard of Europe. There are different types of OATS:
- Outdoor OATS: The cost of the outdoor OATS is very high and so is their accuracy. It is always beneficial to register your Outdoor OATS directly with the FCC so that you no longer need the services of a 3rd party test lab. Depending on the quality of equipment you go for, you can probably put one for around USD 25000.
- Indoor OATS: You can easily recreate an outdoor OATS in a big room. Generally the separation distance between the EUT and the measurement antenna is 3 meters or 10 meters, but you can get away with closer at the cost of accuracy of measurement. This setup, though not exactly OATS, is still useful because you can achieve results which are in close approximation of that of a test lab. But, you will have to face some issues with the ambient noise and reflections. A lot of your time will be consumed in differentiating between the noise coming from your product and the noise in the background.
- Cheaper Indoor Setup: A cheaper option from the above two is implementing a setup with just a hacked together antenna and a low end spectrum analyzer. This would be useful in identifying the problem of a product that has failed at an EMC Test, but it won’t be good for accurate measurements.
ITC India is an NABL accredited testing laboratory providing EMC Testing Services along with many other testing services as per the client’s requirement. Contact b.vig@itcindia.org to get your TESTING QUOTE TODAY or visit our website https://itcindia.org/emc-emi-testing/ to know more about EMC Testing.
EMC Testing 