Inexpensive Microwave Oven Survey Instruments: An Evaluation

Instruments were tested. Depending upon the oven modulation and leak location these tests show that the Micromate will yield a warning reading at levels from 0.6 to 1.9 mW/cm/sup 2/, when the effects of modulation sensitivity and polarization ellipticity are considered. It is to be expected, then, that this instrument will yield warning readings even when the oven emission being measured lies well within applicable standards. Its apparent susceptibility to overload damage, however, could decrease its sensitivity with no clue to the user as to what had happened. Given the same considerations and parameters, the tests show that the Guard-Rod will yield a warning reading at levels from 3.7 to 47 mW/cm/sup 2/, depending on which measurement surface is used. This instrument will sometimes yield warnings for oven emissions lying within applicable standards, and sometimes will fail to yield such warnings for emissions 10 times greater than allowable levels. The same considerations show that the Interceptor/Microscan units will light up at levels from as low as 0.7 to 0.8 mW/cm/sup 2/ or may require levels of 7 to 9 mW/cm/sup 2/. At levels of 28 to 52 mW/cm/sup 2/ or higher, however, the warning LED does not light. If partmore » of the field is cross-polarized, this threshold of extinction may be greater. In any case, there is no apparent way for the user to discern the presence of some potentially hazardous fields, and no way to distinguish such fields from a very low-level field. In summary, instruments of the Interceptor/Microscan design may light up at very low power densities, but fail to light at very high power densities. Clearly, this characteristic is extremely undesirable and potentially dangerous to a user relying on such a device.All of these values assume that the instruments are used in accordance with manufacturer's instructions. Otherwise, results may be worse. Moreover, the range of values given take little or no account of unit-to-unit variation, which may be considerable.« less