In Articles, EMC Testing, Product, White Papers

Select Fabricators Patented Conductive Magnetic door closure design significantly outlasts Conductive Hook-and-Loop door closures on RF Shielded tent enclosures.

Select Fabricators’ RF Engineering team was tasked with testing the shielding effectiveness of the conductive magnetic door seal against a door design using continuous strips of conductive hook-and-loop (velcro) fastener.  SFI’s tabletop and walk-in RF Shielded Enclosures and RF Tents include a patented door wall and door panel that overlap at the two sides and bottom and attach to each other with two continuous strips of flexible high energy magnets.  When the two continuous magnet strips are aligned to close the door around the perimeter of the opening, the conductive fabric layers in between the magnet strips are pressed firmly together forming a very high performance double shielded door seal.  This patented magnetic sealing door design is one of Select Fabricators patented features used on the RF / EMI shielded tent enclosures.  The following picture shows the two rows of magnet strips covered in conductive fabric and attached around the perimeter of the door opening.

RF Enclosure

To test and compare the two door designs, SFI’s RF Engineering department fabricated two identical tents and installed magnet casings on one and the second included two rows of 2” wide silver plated conductive hook-and-loop strips using the same orientation as the magnet casings to provide a double conductive door seal.

Utilizing a battery powered RF transmitter set to 926 MHz, RF shielding effectiveness measurements were taken at the center of the four walls of each enclosure. Each test iteration, when measurements were taken, included placement of the RF transmitter inside the enclosure, calibration of the receiver to the 1 watt output of the RF transmitter, and then closing the door tightly to measure the SE of the four walls. 5000 iterations of this test were done to check for deterioration of the closing mechanism on the tent with the magnetic door seal. 400 iterations were completed for the hook-and-loop door before testing was ceased, as it began to fall drastically below specs and any subsequent data became irrelevant after a certain point. The magnetic door design was measured every 100 iterations due to the large amount of trials necessary. The hook-and-loop door was measured every 10 iterations. For each set of measurements, the average reading was calculated.

The data was organized into a color-coded chart, see below, wherein the shielding effectiveness values of 79dB and up are highlighted in green, the values between 60dB and 79dB are highlighted in yellow, and the values below 60dB are highlighted in red. This offers a visual depiction of the range-based integrity of each tent over time. Only the first 400 test iterations are shown for the magnetic door in this chart.

Magnets vs Velcro

The following graph shows the rolling average shielding effectiveness of the enclosures for all 5000 test iterations of the double magnet door seal and the 400 test iterations of the conductive hook-and-loop door seal.

Magnets vs Velcro

SFI Patented Magnetic Closure vs Velcro Closure – Shielding Effectiveness over time

 

 

 

 

 

 

 

 

 

 

 

 

 

The results of this comparison show clearly that the magnetic style of door sealing is more effective long-term and over usage than the conductive hook-and-loop door closure; this implies that the hook-and-loop fastener wears down much faster than the magnetic strips covered in conductive fabric and degrades much more rapidly.  While the magnetic strip casings hold up for thousands of trials, the hook-and-loop strip only maintains its integrity for about 50 trials before it begins to show signs of weakening.

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