f you’re technically-minded and involved in EMC testing, then you’re probably well aware of all of the nerdy things involved in running an EMC test facility, properly outfitted with the best semi-anechoic chamber(s) and associated test equipment and cabling. To the exact letter of the law (i.e., standard), you already know how to set up and perform an accurate and repeatable radiated emissions or RF immunity scan. You know how ferrite tile and RF absorber works and which antenna(s) work best for each particular type of EMC test. You’re an expert at EMC testing but, when it comes to installing, tearing down, and moving an EMC chamber, you may not have a clear understanding of all of the non-engineering tasks that go along with such an important event.
The following information points out just a few of these important considerations, which, if correctly taken into account and appropriately executed, will make the process of installing, tearing down, and moving an EMC go much more smoothly.
Include in the above-mentioned list, information such as contact information for the organization, who will contact them and when the actual date contact is made, what paperwork or other information is required, who will complete the paperwork, when the paperwork will be submitted, when it is required, and when it is submitted and approved. If this information is not tracked in such a detailed and organized manner, then it’s almost certain that a required permit or another important task will not get completed in time for the chamber install (or chamber move), resulting in a schedule or other harmful delay.
- User/buyer asks for a revision to the drawings after they had originally given final approval. What are some reasons that the user/buyer may require a late revision to a drawing? Here are just a few examples:
- ⚬ The type of penetrations and locations of the bulkheads not thoroughly thought through or specified upfront.
- ⚬ The size of doorways, ramps, and other critical dimensions such as ceiling height and quiet zone size determined to be inadequate based on the size of the EUT.
- ⚬ Number and types of power outlets and associated filtering for power frequency and higher RF signal frequencies are overlooked and not specified.
- Standard height loading dock not available at load/unload site.
- No arrangements prepared for the manipulation, secure staging, and secure storage of install/move equipment and chamber hardware, crating/uncrating, removal of waste material, etc.
- Forklift and forklift operator not available when needed.
- The parent room floor is not level and extra effort is required to install the chamber on a level plane.
- Housekeeping power outlets are not provided for powering installation tools.
- Services for the removal of trash and other construction debris are not provided.
- Sufficient air circulation throughout cementing and other odor-producing processes is not provided.
- Ownership of mechanical and electrical attachment between the parent building and chamber incorrectly assumed to reside with the chamber installer and not with the user/buyer.
- Access to the installation site during all necessary and available work times not provided (days, nights, weekends as required).
- Any specialty security measures at the worksite are not properly coordinated or communicated to the installation team.
- Minimum and maximum safe working temperatures are not provided.
- Worksite does not contain sufficient illumination, and other arrangements for proper lighting are required.
- Shielding effectiveness (before absorber is installed)
- Normalized Site Attenuation (NSA)
- Field Uniformity (16 point per IEC 610004-3)
- Site Voltage Standing Wave Ratio (sVSWR)
- Modeled long wire absorber-lined shield enclosures (ALSE) measurement (required for automotive EMC testing)
- IEEE 299 (2006) – IEEE Standard Method for Measuring the Effectiveness of Shielding Enclosures.
- ANSI C63.4-2014. American National Standard for Methods of Measurement of Radio-Noise Emissions from Low-Voltage Electrical and Electronic Equipment in the Range of 9 kHz to 40 GHz.
- CISPR 16-1-4:2010. Specification for radio disturbance and immunity measuring apparatus and methods – Part 1-4: Radio disturbance and immunity measuring apparatus – Antennas and test sites for radiated disturbance measurements.
- IEC 61000-4-3 :2006+AMD1:2007+AMD2:2010 (consolidated version). Electromagnetic compatibility (EMC) – Part 4-3: Testing and measurement techniques – Radiated, radio-frequency, electromagnetic field immunity test.
- RTCA DO-160G. Environmental Conditions and Test Procedures for Airborne Equipment (08-Dec-2010).
- CISPR 25:2016. Vehicles, boats and internal combustion engines – Radio disturbance characteristics – Limits and methods of measurement for the protection of on-board receivers.
- ISO 11452-2:2019. Road vehicles – Component test methods for electrical disturbances from narrowband radiated electromagnetic energy – Part 2: Absorber-lined shielded enclosure.
- Selection of a chamber is determined by the standard being tested to. Some types of EMC Chambers are: Commercial, MIL STD/DO-160, CISPR 25 and Reverb.
- Commercial chambers are used for IEC and CISPR standards for Emissions and Immunity testing. Typically, “Semi – Anechoic” and achieve CISPR16 (Emissions) and IEC 61000-4-3 (Immunity) chamber performance requirements.
- Semi-Anechoic Chambers are strategically lined with absorber and ferrite to meet specifications without fully lining all surfaces.
- Verification for CISPR 16 compliance is Normalized Site Attenuation (NSA) (26 MHz-1 GHz) and Site Voltage Standing Wave Ratio (sVSWR) (1-40 GHz). This verifies the chamber “Quiet Zone”. Quiet zones are normally equal to the turntable diameter. EUTs can’t be larger than the quiet zone.
- For compliance, variations in the quiet zone performance cannot exceed +/-4db for NSA and 6dB for sVSWR.
- Verification for IEC 61000-4-3 is a field uniformity test. Typically, a 1.5m x 1.5m vertical plane consisting of 16 points spaced 0.5 m apart is the measured area. At least 12 Points must vary by <6dB.
- MIL STD and DO-160 chambers can be Semi-Anechoic or Fully Anechoic. Standards require the absorber have a minimum absorption of 6dB from 80MHz to 250MHz and 10dB above 250Mhz. A table with a conductive top is bonded to the shield ground is used for testing the EUT.
- CISPR 25 chambers are fully lined on walls and ceiling, contain a similar table with metal lining on top, and must pass the Long Wire Test or the Reference Site Method test to meet the Standard.
- Reverb chambers rely upon the reflectivity of the walls and an internal movable paddle to reflect generated signals and increase the value of V/m generated from the transmit antenna.
- Information needed to design a reverb chamber is the lowest frequency, the test volume, maximum V/m, and standard to be tested to (MIL STD, DO, ISO).