Measurements and Reduction of Microwave Oven Electromagnetic Leakage

INTRODUCTION:

Public believed that radiation leakage from microwave ovens was similar to atomic radiation that could lead to serious health problems, including cancer. For many years up to now, domestic microwave ovens were not considered to leak levels of microwave radiation that caused concerns; consequently, they have not been regularly monitored. According to Australian Standard 3301, the maximum allowable leakage from a microwave oven is 5 mW/ cm² at 5 cm distance from the oven surface.

METHODOLOGY:

In order to investigate the effects of microwave oven leakage, several experiments have been conducted in the chamber room. Figure 1 shows the orientation of device under test which is microwave oven in the chamber room. The electric field probe is used to measure the power density that is produced by the microwave oven. All the data are displayed through the ProbeviewLT software as shown in Figure 2. Firstly, each element's output is measured, the vector sum is determined, and the results are calculated as in equation below,

Next, a point where the maximum emission produces is determined and monitored by ProbeViewLT software.

        

There are six measurements have been conducted for various types of microwave ovens. All the microwave ovens gave the power densities below the reference standard which is 5 mW/cm² except the microwave oven from Brand A. Figure 6 shows the power density in mW/cm² for six microwave ovens that have been measured based on the point illustrated in Figure 3.

RESULT AND ANALYSIS:

From the graph (Figure 4), the maximum point at coordinates (17.75, 16.66) cm gives the maximum power density 10.19 mW/cm² and exceeded the standard of 5 mW/cm². This is due to the Brand A microwave oven is tested in dirty condition and has been used for a long time. Based on the measurement, the high power densities are detected at point 7, 8, 9, 12, 13 and 14 compared to other points. These points are located in the middle of the microwave oven which is on the glass panel.

    

One of the solutions for reducing the microwave oven leakage is by using Conductive  Transparent Film as shown in Figure 5. The Conductive Transparent Film able to shield electromagnetic waves in electronic equipment and its also useful for providing various transparent structures with antistatic properties while keeping transparency of the structures. An electrically conductive transparent film has conventionally been formed on an electrical insulating. In order to reduce the microwave oven leakage, it is suggested that the Conductive Transparent Film is applied on the glass panel inside the microwave. 

Figure 6 shows the power density in mW/cm² for Brand A Microwave Oven before and after applied the technique to reduce the electromagnetic leakage due to Microwave Oven. Based on the graph, it shows that the Conductive Transparent Film can reduce the microwave oven leakage by about 12.39 dB to 8.53 dB.

CONCLUSION:

There are six measurements have been conducted for different types of microwave ovens including new and used from various models. According to the measurements, it is found that all of the microwave ovens are having leakage. The leakage are including not exceeded and exceeded the limit of microwave oven leakage. From the measurements data, the statistical relates to the leakage of microwave oven electromagnetic energy is produced and it is suggested to use Conductive Transparent Film to reduce the leakage from the microwave oven, since it is a relevant way in shielding to prevent unwanted leakage from the microwave oven.

Written by: 

Nooradzianie Muhd. Zin, Najwa Nasuha Mahzan and 

Ku Siti Syahidah Binti Ku Mohd Noh