Answer to Question #11645 Submitted to "Ask the Experts"

Category: Instrumentation and Measurements — Surveys and Measurements (SM)

The following question was answered by an expert in the appropriate field:


I used a Rad*Scanner Model 500VBR Geiger-Mueller (GM) detector to test a device which is advertised to put out radiofrequency (RF) radiation (not x rays) to treat the skin. The device has a glass tube with a metallic end and no filament; the metallic end is energized. I thought this looked strange so I used my GM detector and after one minute it read 1,400 counts per minute (cpm) and after five minutes it read 5,400 cpm. I put this device and the GM detector in a metal box and activated it by a circuit far away. When I opened the box there was a distinct vaporous odor, which I didn't recognize. The Rad*Scanner manufacturer wonders if it's not x rays but rather electromagnetic interference, and so the manufacturer suggested I run an AM radio to check for signal interference. Since I don't want to be around the device while testing it, I was going to digitally record the sound while it ran. Is there a better way to test for x-ray output?


It is extremely unlikely that the RF skin treatment device is producing x rays. Using the AM radio, as was suggested, may tell you that RF is present, but that does not tell you whether the response on your GM was also caused by the RF. You should be able to do a quick test by having a fixed distance between the GM instrument and the RF source and making a measurement with the GM. Keeping the same distance between GM and source, place a piece of aluminum foil between the GM detector and the source, making sure that the entire RF source is blocked from view of the GM instrument with at least several centimeters of aluminum foil extending beyond the length and width dimensions of the source. It is sometimes desirable (but often not necessary) to ground the aluminum by connecting a conductor from it to a water pipe or other grounded conductor. Take a reading on the GM in this configuration. If the reading is markedly reduced compared to the unshielded reading, the radiation likely causing the response on the GM is the RF radiation, which can induce currents in various components of the instrument. If the reading on the GM detector remains pretty much the same with the foil in place as when no foil was used, then there is the possibility that x rays might be involved, in which case more investigation would be appropriate.

Don't place the source and detector in a metal box when you do this or any other tests since the box will cause multiple RF reflections and standing wave patterns that can affect the GM response, and can severely damage the instrument as well as the RF source. When the RF source is placed in a metal box enclosure, various standing wave patterns may be produced within the enclosure, and it is possible that there may be numerous "hot spots" where RF energy is concentrated. Concentrated RF energy can cause possible buildup of charge and actual electrical discharges to conducting surfaces/items in the enclosure, as well as heat buildup in various materials. The odor that you detected could have been from ozone produced by an electrical discharge or possibly may have been some volatile component released from an insulator or other component in the detector or source as a consequence of heat buildup or discharge.

George Chabot, PhD

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