Journal of Microwave Power and Electromagnetic Energy (JMPEE)
TITLE	Performance of a Liquid-crystal Microwave Oven Leakage Indicator [PDF]
AUTHORS	W. A. G. Voss and R. Turner 1982 17 1 39-50
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Abstract The development, performance, and reliability of the Micro-Check (TM), 2,450-MHz radiation detector are discussed. The device is a self-powered microwave oven door leakage indicator, which uses liquid crystals responding to the temperatures of an array of thin-film carbon resistors. The thin film resistors intercept a leak and partially terminate it at the source along the door gap. A response, in the form of a distinct colour pattern, occurs within 10 seconds if the leakage exceeds the normal product Emission Standard (≥ 5 mW/ cm² when measured 5 cm from the surface) for the majority of door designs. For five different door geometries tested, the response time for a major leak (>20 mW/cm²) was ≤ 2 seconds. Reliability tests for response time, aging, temperature effects, and microwave radiation overload to the point of destruction were performed on more than 30 production samples. The conditions under which a false indication of a leak (i.e., < 1 mW/ cm² when measured at 5 cm from a surface) might occur are studied and this problem does not, in practice, appear to exist. It is concluded that a small, reliable indicator of microwave oven leakage, that will show the extent of a leak along a door gap, is now available for use by the general public. Major advantages are reliability and simplicity of use over a wide range of ambient temperatures.