ELECTROMAGNETIC (EMI) TESTING

 

Introduction:  Two anechoic shielded testing facilities are available for performing Electromagnetic Compatibility (EMC) tests. These facilities meet electromagnetic performance requirements specified by MIL-STD-462, and support the performance of EMC tests specified by MIL-STD-461-C/E/F and the GSFC "General Environmental Verification Specification" (GEVS). Both facilities provide very low level ambient electromagnetic environments and the ability to contain internally-generated, radiated electromagnetic waves. All electrical power, communications, and other facility wiring are filtered; the facility structures are locally bonded to earth ground; and ventilation ducts and other apertures are designed as waveguide-below-cutoffs. Contamination-sensitive items are tested in the Large EMC Facility (Class 10k cleanroom), or they are bagged in non-reflective materials (Melonex) if tested in the Small EMC Facility.

 

Integral Instrumentation:  Generated interference measurements are typically made using a Rohde and Schwarz EMI receiver system (ESU8/40 and ESIB40) for data acquisition, processing, and data reduction. Associated electric and magnetic field antennas and line conduction transducers are provided for testing in the 20 Hz to 40 GHz frequency range. The receiver system is controlled by the Rohde and Schwarz EMC32E/S measurement software package. Line conducted and radiated susceptibility tests are performed using a variety of signal generators, amplifiers, and transducers or antennas for injection and/or radiation of the test signals. Frequency range is 20 Hz to 400 Mhz for signal injection; 10 kHz to 40 GHz for signal radiation. Radiated field strengths up to 200 V/m can typically be provided. Programmed swept frequency test signals, appropriately modulated, are provided over portions of the test spectrum.

 

Data Acquisition:  The Rohde and Schwarz EMC32E/S EMC measurement software can be used for all Electromagnetic Interference (EMI) and Electromagnetic Susceptibility (EMS) measurements. The software is a modern and powerful tool for controlling and monitoring devices/equipment. Susceptibility test data relating to the susceptibility test signal can be time synchronized with the test item performance test data which is typically recorded as a function of the type of ground support equipment (GSE) furnished with the test item. Failure modes are test project defined and susceptibility thresholds determined whenever the test item responds to the susceptibility test signal.

 

Electrical Power:  Test item power is normally provided by project-furnished, current and/or voltage limited power supplies. AN Elgar 5250 Switching Amplifier can be supplied for power quality tests that desire spacecraft specific power ripple tests. Each anechoic chamber is supplied with 100W of filtered power and can be modified to handle higher power applications with the proper amount of preparation.

 

Highlights include:

• Two independent test facilities provide a minimum of 20dB absorption (small facility) and 6dB absorbtion (large facility) of normally incident electromagnetic waves, above 20 MHz

• Contains internally-generated, radiated electromagnetic waves with a combination of energy-absorbing panels and wall-mounted ferrite tiles for optimized anechoic performance

• Conduct magnetic dipole moment testing and spacecraft magnetometer calibration in a 9.5-ft diameter Helmholtz coil facility

 

Click on any facility photo below for more detailed information/specifications

Facility 421:  Large EMC Facility

 

Description:  This facility is designed for testing large spacecraft that require Class 10k contamination protection. This facility consists of three contiguous electromagnetically shielded enclosures that meet or exceed shielding enclosure requirements stated in MIL-STD-285 and IEEE-299. The enclosures consist of the Test Room, the EMC Control Room, and a Ground Support Equipment (GSE) Room. Inside the enclosure is a free-standing faraday cage that is lined with ferrite tiles with Panashield HYB-NF12, fibrous composite material with carbon  impregnated within wedge absorbers to handle RF energy absorption up to 200 V/m (70 mW/cm2) from 20 Hz to 40 GHz. The Control and GSE Rooms consist of standard modular shielded panels constructed of 3/4" plywood paneling, sandwiched by an inner and outer layer of 10 mil galvanized steel. A cable penetration plate, located on the same wall asa the test bench, separates the Test Room from the GSE Room and acts as a Single Point Ground for both the spacecraft and GSE.

 

Mode of Operation:  The test article is installed inside the faraday cage and bonded to the penetration plate ensuring a single point ground for project and EMI test equipment. Grounding for larger spacecraft, that can't fit onto the test bench, can connect to either an 18" or 36" wide copper strap for a better RF ground and maintaining a 5:1 (L:W) ratio. Interconnecting cables between the test article and its ground support equipment are connected through an access panel mounted either on the cleanroom or GSE side, allowing for greater flexibility and acting as a single point ground. The test enclosure maintains a relative humidity at a value between 30% and 70% and temperature at 68F +/- 5F (20C +/- 2.8C).

 

Rental Rate:  Inquire

(Facility 421 specifications)

Facility 425:  22ft Coil Magnetic Test Facility

 

Description:  The Magnetic Field Component Test Facility (MFCTF) contains a 6.7m (22') diameter spherical coil system. This system provides geomagnetic field cancellation within a 0.9m (3;) diameter sphere to levels described in the specifications list. This coil system is used primarily for testing smaller satellites, performing instrument-level dipole moment measurements, and for calibrating magnetometers and attitude control systems

 

Mode of Operation:  For a typical magnetometer test, a zero field is established in the center of the coils before the test unit is sinstalled. A reference standard proton magnetometer is then used to calibrate the system. Following this, the test magnetometer is positioned on the platform at the center of the coil and aligned to the coil axes. Finally, static and dynamic fields are generated to establish the linearity, frequency response, zero offset, and alignment characteristic of the magnetometer.

 

Rental Rate:  Inquire

(Facility 425 specifications)

Facility 426:  42ft Coil Magnetic Test Facility

 

Description:  The Spacecraft Magnetic Test Facility (SMTF) 12.8m (42') coil system is one of the three known spherical coil systems of this size in the world. Its geomagnetic field cancellation system is capable of cancelling the Earth's magnetic field within 1.83m (6') diameter sphere. The SMTF also has a set of 2.90m (9'6") diameter Helmholtz coils available for perming and deperming spacecraft, and 1.22m (4') and 1.83m (6') diameter coils for magnetically cleaning smaller test items.

 

Magnetic Dipole Moment Testing:  Zero-field is first established in the center of the coil. A reference standard proton magnetometer is used to calibrate the coils. For each measurement sequence, the test item and facility dolly are moved to the center of the coil. As the dolly is rotated 360 degrees, three-component magnetic field data is obtained at 10-degree increments. The data is then stored in the computer for immediate display and processing. If the test item exceeds its test limit, compensation magnets can be developed to reduce the dipole moment to acceptable levels.

 

Rental Rate:  Inquire

(Facility 426 specifications)