Raising the bar for EMI testing
Greg Reed, Contributing Technical Editor -- Test & Measurement World, 4/1/2006
 |
| JIM PRESS National Director of EMC/EMI National Technical Systems Courtesy of NTS. |
Q: What were the primary technical and business challenges in building up the facility infrastructure?
A: The main technical issues involved ensuring that the test chamber was designed to handle the high field strengths produced during the testing. This included ensuring that any egresses for cables or for support lines such as air or hydraulic lines were properly shielded and that any anechoic material had the proper rating to handle any heating caused by the field. Technicians had to be trained on using high-power amplifiers and the associated cables, waveguides, and antennas. It is quite easy to destroy an antenna with 2500 W.
The main business challenge was training the sales force on the new capability and keeping the stockholders happy about the return on investment. In addition, we had to upgrade two facilities simultaneously—Plano and Boxborough.
Q: What is the significance of providing 200-V/m EMI testing?
A: 200 V/m is required on almost all critical military equipment that is exposed to weather. This would include systems located on the deck of a naval vessel, located on the fuselage of an aircraft, or located on the roof of a ground facility. Also, 200 V/m testing applies to space and missiles systems, although these include probably less than half of all major systems procured by DoD.
Q: How do MIL-STD-461 and RTCA DO160 specifications impact or govern test equipment setup?
A: Both MIL-STD-461 and DO160 have recommended test setups that should be followed. Luckily, the setups are similar, which minimizes training. Both standards have guidance on the intent of the setup rather than a strict must-follow setup, unlike some other commercial standards that have strict setups that sometimes do not fit the application.
Q: Besides aircraft, what other military systems are subject to 200-V/m testing?
A: As mentioned above, all critical equipment exposed to weather needs to meet 200 V/m. The reason is the dense external electromagnetic environment on the platforms and ground facilities. Take a look at a Navy ship, fighter aircraft, or a ground shelter; it can be difficult to find the armament and weaponry since these are obscured by all the antennas used for communication, air search, location, and numerous other uses.
Q: What are some commercial aviation concerns that warrant 200-V/m test?
A: Commercial airports have radar and communication antennas that are similar to those in military platforms and facilities. This is the reason for high levels of testing for commercial airliners. If the search radar knocks out the engine controller during take-off, we'll all have a bad day.
Q: Do test personnel require extensive training on the new equipment?
A: Our technicians were already performing lower-level testing (100 V/m and less), which is required for equipment not exposed to the weather. The 200-V/m training was geared toward handling the high-power amplifiers and not on test setup or new techniques.
