Has MED-E-Shield^TM Been Tested?

Yes, MED-E-Shield^TM has been tested! We have third party verification from two independent certified EMC testing labs regarding this mobile conductive enclosure. These reports describe the shielding effectiveness of the structure. Shielding effectiveness measures just how well the enclosure attenuates the range of electromagnetic waves generated in the testing lab during the session. MED-E-Shield^TM has also been tested in a medical clinic environment with a physiatrist and live EMG study.

To understand how well MED-E-Shield^TM works in blocking EMI and RFI, it is important to look at the highlights of the testing results. In the most recent study, performed in early September, 2008, the enclosure was exposed to a broad band of electromagnetic interference through a frequency range from 150kHz up to 18GHz. These waves are generated by a signal generator and are directed at the enclosure by a special horn antenna. Inside the enclosure is an EMI receiver. The shielded room is tested directly from all four sides and the roof to determine any differences in performance electromagnetically in these surfaces.

In these studies, the shielding performance is measured in dB’s. A higher dB number indicates that you have achieved greater shielding effectiveness! Just to give some sort of benchmark, most companies that are required to go through stringent MIL-461 or UL or CE mark testing of their products are trying to hit 40 to 60 dB of effectiveness to be “compliant”. Most of these companies are also not being put through a broad spectrum of frequencies. Therefore, they have the luxury of designing for either a low or high frequency range. It is difficult to achieve good results across the broad spectrum. MED-E-Shield^TM has achieved these levels of attenuation and higher from 150kHz up to 18GHz! See the table below (Table 1) for these results. In the “Open” column the numbers reflect the shielding effectiveness with the door to the unit left completely open. A negative number is “no” shielding whatsoever!

Table 1  Shielding Effectiveness Data (All values below are Attenuation value in dB’s)
		SHIELDING EFFECTIVENESS WITH DOOR CLOSED (dB’s)
Frequency	Door Open	Door Side	Right Side	Left Side	Rear Side	Roof
150kHz	-11	58	69	66	64	70
14MHz	-25	35	35	48.2	25	25
26 MHz	-10	49	55	56	48.7	63
300 MHz	1	80	81	77	78	81
400 MHz	0	78	75.7	78	75	76
800 MHz	-2	78	73.7	83	71	74
1GHz	-14	58	74	79.1	72.4	74
3 GHz	-12.8	65.1	80.2	78.2	77.2	80
6 GHz	-20.9	71.1	81.1	75.4	69.8	81
10 GHz	-21.7	71.7	80.3	77.3	69.3	80
12 GHz	-21.7	75.7	80.3	76.5	69.4	80
14 GHz	-22	75.4	80	81	67.7	80
16 GHz	-25	74	77	73	63	77
18 GHz	-35	68	67	68	65	67

The key here is to understand that our “Mobile Enclosures for Diagnostic Equipment” perform at very high levels in blocking out harmful EMI (Electromagnetic Interference) and RFI (Radio Frequency Interference). Maybe even more important is that the enclosures do this across a spectrum of interference that is much broader than is tested normally. Now we will turn our attention to the specific application of shielding out “noise” during a Nerve Conduction Study (NDS) or an EMG.

While EMC testing labs have a variety of specific equipment to generate and detect Electromagnetic and Radio Frequency Interference, a doctor’s office, operating room or clinic settings do not. However, in each of these settings there can be and often are pieces of equipment that generate this EMI/RFI “noise”. This can be very disruptive to the EMG machine. Buildings that are not well grounded (quite a large percentage are not!) also cause problems with emissions that disrupt the EMG and NCS. Remember the conducted emission? In a building that has poor grounding, extraneous currents are picked up all the time and run along wiring to outlets. Sensitive equipment (EMG machine) will pick up this current and usually a 60 cycle wave or harmonic will be visible on the monitor. So how do you deal with all of this noise?

MED-E-Shield^TM is exclusively designed to filter out both the radiated and conducted emissions that interfere with the NCS and EMG’s. To prove this, we took MED-E-Shield^TM to Fresno, California and tested it at the California Industrial Rehabilitation Center located at 2841 Tulare Street. This was done early in 2008. Facility owner and operator, Mr. Alvaro Valenzuela and his son Mr. Nico Valenzuela were extremely gracious and helpful in facilitating the use of equipment and their outpatient surgical center operating room. Dr. Thomas J. O’Laughlin, Medical Director of the Rehab Center and AAPMR member, supervised and performed the actual EMG studies on patient Terry O’Laughlin.

The test for the enclosure was set up and supervised by Mr. Michael Oliver, VP of Electrical and EMC Engineering for MAJR Products Corporation. In this test, the MED-E-Shield^TM enclosure was set up in the operating room where a number of “noisy” pieces of equipment resided. All of the equipment was turned on and Dr. O’Laughlin then proceeded to start the EMG machine and study outside of the shielded enclosure but inside the operating room. There was so much extraneous activity on the monitor it was deemed impossible to get a reading on the patient. Then the EMG equipment, Dr. O’Laughlin, patient Terry O’Laughlin and Mr. Oliver all moved into the MED-E-Shield^TM enclosure. Just to demonstrate to Dr. O’Laughlin what was about to happen, we had him look at his cell phone which was on and fully functioning. Then Mr. Oliver closed the door to the shielded room. No cell service! All the bars were gone and Dr. O’Laughlin could not operate his phone. The door was opened back up a bit and the phone again was functioning.

Dr. O’Laughlin then prepared the patient for the EMG study. The EMG machine was turned on. No artifacts appeared on the screen! A flat baseline was available to begin the study and Dr. O’Laughlin proceeded to test a deltoid muscle on the patient. Clean, readable wave patterns emerged on the monitor and the test was a complete success.

All testing of our mobile enclosures up to this point in 2008 show verifiable, remarkable levels of protection against EMI and RFI, both radiated and conducted. Call or email us to find out how you can purchase or rent MED-E-Shield^TM!