3 ms·

Test for microwave leaks by putting a cell phone inside and calling it?

3 points by chdir 12y ago

lutusp 12y ago
The problems with testing a microwave oven's shieding effectiveness using a cell phone are legion: 1. The frequencies used by cell phones (typically 0.8 GHz in the U.S.) aren't the same as those used by an oven's magnetron (2.45 GHz), so we're comparing apples and oranges. The only valid test of shielding must necessarily use the same frequency as the microwave's magnetron. 2. The signal attenuation required to render a cell phone inoperative is not nearly enough to assure a person's safety when a magnetron is in operation. A power attenuation of 20 db (meaning reduction by a factor of 100) will almost certainly render a cell phone inoperative, but cannot assure safety to a person standing near a typical consumer microwave oven generating 0.7 kilowatts (700 watts) of microwave power and therefore emitting 7 watts into its immediate environment. I emphasize the second example is hypothetical, meant only to show that an attenuation more than adequate to prevent the cell phone from working, is not nearly enough to assure a person's safety, not that this is a typical microwave oven leakage power.
- chdir 12y ago
  > an attenuation more than adequate to prevent the cell phone from working, is not nearly enough to assure a person's safety On the contrary, if the shielding is ineffective to stop even the cell phone from working, can it be concluded that it definitely won't stop the 2.4GHz radiation. Hence there's a radiation leak. Update: To answer my own comment, quoting from the source : "Traps and seals that work well at 2.45 GHz might not work so well at lower frequencies. It is true that apertures below cutoff have a shielding effectiveness that improves as frequencies get lower. However, the absorption loss associated with shielding materials gets worse at lower frequencies. Since microwave ovens operate in a very narrow frequency band, their shielding can also be narrow band. "
  - lutusp 12y ago
    >> an attenuation more than adequate to prevent the cell phone from working, is not nearly enough to assure a person's safety > On the contrary, if the shielding is ineffective to stop even the cell phone from working, can it be concluded that it definitely won't stop the 2.4GHz radiation. Hence there's a radiation leak. "On the contrary"? You ended up agreeing with me. > To answer my own comment, quoting from the source : "Traps and seals that work well at 2.45 GHz might not work so well at lower frequencies. The converse is also true. Depending on shield design, a shielding scheme meant for one frequency may not work at all well on another. My original claim was that the cell phone test is no assurance of microwave oven safety, for multiple reasons.

3 points by chdir 12y ago

The problems with testing a microwave oven's shieding effectiveness using a cell phone are legion: 1. The frequencies used by cell phones (typically 0.8 GHz in the U.S.) aren't the same as those used by an oven's magnetron (2.45 GHz), so we're comparing apples and oranges. The only valid test of shielding must necessarily use the same frequency as the microwave's magnetron. 2. The signal attenuation required to render a cell phone inoperative is not nearly enough to assure a person's safety when a magnetron is in operation. A power attenuation of 20 db (meaning reduction by a factor of 100) will almost certainly render a cell phone inoperative, but cannot assure safety to a person standing near a typical consumer microwave oven generating 0.7 kilowatts (700 watts) of microwave power and therefore emitting 7 watts into its immediate environment. I emphasize the second example is hypothetical, meant only to show that an attenuation more than adequate to prevent the cell phone from working, is not nearly enough to assure a person's safety, not that this is a typical microwave oven leakage power.

chdir 12y ago
> an attenuation more than adequate to prevent the cell phone from working, is not nearly enough to assure a person's safety On the contrary, if the shielding is ineffective to stop even the cell phone from working, can it be concluded that it definitely won't stop the 2.4GHz radiation. Hence there's a radiation leak. Update: To answer my own comment, quoting from the source : "Traps and seals that work well at 2.45 GHz might not work so well at lower frequencies. It is true that apertures below cutoff have a shielding effectiveness that improves as frequencies get lower. However, the absorption loss associated with shielding materials gets worse at lower frequencies. Since microwave ovens operate in a very narrow frequency band, their shielding can also be narrow band. "
- lutusp 12y ago
  >> an attenuation more than adequate to prevent the cell phone from working, is not nearly enough to assure a person's safety > On the contrary, if the shielding is ineffective to stop even the cell phone from working, can it be concluded that it definitely won't stop the 2.4GHz radiation. Hence there's a radiation leak. "On the contrary"? You ended up agreeing with me. > To answer my own comment, quoting from the source : "Traps and seals that work well at 2.45 GHz might not work so well at lower frequencies. The converse is also true. Depending on shield design, a shielding scheme meant for one frequency may not work at all well on another. My original claim was that the cell phone test is no assurance of microwave oven safety, for multiple reasons.