Microwave oven question

[TheNiceGuy]

If my oven was leaking, would I be able to feal it?
What if it was leaking toward your eyes?

 

[SonicIce]

i guess it depends on how much was leaking. i saw one once where the top of the door was melted a little bit probably from a leak.

the question is how much does it take for a person to feel. i dont know

 

[ShawnD1]

I did a google search for "microwave frequency" and the answer is about 2ghz. We can use this value to calculate the wave size.

distance = (speed) / (frequency)
distance = (3E08 m/s) / (2E09 1/s)
distance = 0.150m

0.150m is about 5.9 inches. The waves shouldn't leak out unless there's a huge hole in the microwave.

The very large waves are why we can have a mesh with holes big enough to see through and still be protected from the waves

 

[PsiStar]

1/4 wavelength is actually the magic number & it only needs to be a slit.

Microwave frequencies heat tissue ... thus the use in microwave ovens! You not be able to feel a small leak. Guess what frequencies Bluetooth operates at ... just above 2 GHz. Ironic? But they are considered safe.

Larger leak ... again ... heats tissue. You so do *not* want to feel it. If you suspect that you have a leak, you might be able to find a repair shop with a tester. Although I bought a tester from a hardware store close out several years& I know I did not pay much for it. I probably used it twice & it is one of those things laying in the bottom of the tool box. You also do not know how good they are ... so thinking out loud, if you suspect, then find a repair shop, or just replace if a cheapy, or don't stand close. Power drops per 1/(radius x radius)

 

[NoQuarter]

The guy who realized you could cook food with microwave radiation had a chocolate bar melt in his pocket while working on some radars. I would run a chocolate bar along the door frame to check for leaks, the rest of it is pretty well sealed.

 

[Paperdoc]

In graduate school I did research using microwave systems and, being cautious, refused to buy / use a microwave oven at first precisely for this reason - how do you now if the oven has a problem? The truth is, at levels of microwave leakage that MIGHT be hazardous - and the human retina, being the most sensitive exposed tissue, is the most vulnerable to damage from small leaks - you can NOT detect it yourself! Any leak large enough for you to FEEL with your hand as heat would be HUGE compared to safe exposure levels.

I HAVE been using microwave ovens for years in our home, though. There are three things you can and should do to be confident of safe performance.

1. Keep it clean - especially around the door - so that the door does close smoothly and properly.
2. For exactly the same reason, if you have physical damage to the unit that interferes with door fit, get it fixed!
3. If you REALLY want to test and verify proper performance, get a service shop with the right equipment and know-how to test it. The fact that you almost cannot find a home test instrument any more in stores is an indicator that this is an uncommon concern these days.

 

[parim]

3. If you REALLY want to test and verify proper performance, get a service shop with the right equipment and know-how to test it. The fact that you almost cannot find a home test instrument any more in stores is an indicator that this is an uncommon concern these days.

There is a easy way to test if your microwave`s faraday cage is working,
Place a wifi device like a Phone that is connected to an access point in the microwave and shut the door. now check if you can ping the phone. if you can then there is a problem with the microwave.

The reason this test works is because most microwaves work at around 2450MHZ which is very close to the Frequency baund that WIFI uses 2400MHz

 

[TheNiceGuy]

The reason I ask is that we recently bought an expensive microwave, which was later damaged. The front glass was smashed our, and the whole thing banged a bit, but the metal frame/cage look OK. Several timesa day I use it, and have to stare at the stuff I am heating up (to make sure it doesnt boil over). I also started getting problems with one of my eyes afterwards, although i really think it is just a coincidence. I have never "felt" anything from it, but am still curious. The front cage is dented, but looks solid.

 

[microwaveguru]

As long as the mesh is intact there shouldn't be a problem. Even if there were some leakage, it has to be very large in order for you to feel the warmth - that will only occur if there was a sizable hole - greater than 1/4" - in the mesh.

 

[Modular]

How much is a microwave these days? Go out and replace it if you suspect it's leaking. Why even mess with it?

 

[Modelworks]

For about 5 years cell phones were allowed to emit more than a microwave was allowed to leak under health rules. They have since revised that. But the idea that they thought a microwave oven was dangerous when it leaked a tiny amount compared to a cell phone that is held at your head, always made me laugh.


You can make a cheap detector out of a LED and a schottky diode (cathode to anode, anode to cathode), leave the leads long. Moving it around the microwave casing will cause the led to light at points that leak RF. You can do the same thing near radio and tv transmitters.

 

[DominionSeraph]

I wouldn't trust a microwave with that level of damage. The door gap is where leaks are most likely to occur, and what's the chance that the door frame and hinges are in perfect shape?
While the diode detector would give you a definite positive, I wouldn't use the negative as indication of anything.

If it were mine, unless I had a spec an to check it out, it'd be junked.

 

[Red Squirrel]

Ask these guys, they have plenty of experience doing stuff with broken microwaves.

http://www.youtube.com/user/JPizzle1122

 

[TheNiceGuy]

Thanks all!

How about feeling any leaks? Anyone know about that? I'd imagine that it would hurt a lot, becasue it would boil water in tissue. Would very low leaks be unfelt? Cause cancer? Or...?

Also, i remember someone saying sparks(ala tinfoil, gold rims, etc) is bad because it 'causes arching' (whatever that is) and can damage the lining. Is that true? And are sparks dangerous at all?

Thanks!

Funny link BTW!

 

[PsiStar]

There is a easy way to test if your microwave`s faraday cage is working,
Place a wifi device like a Phone that is connected to an access point in the microwave and shut the door. now check if you can ping the phone. if you can then there is a problem with the microwave.

The reason this test works is because most microwaves work at around 2450MHZ which is very close to the Frequency baund that WIFI uses 2400MHz

This is a great idea!

Even enable Bluetooth on the phone & see if you can find it with another device. I think I'll check out my microwave oven leakage detector with this to see if there is any correlation.

Maybe there should be a ATOT post your results here thread?????? With the wifi or Bluetooth test???

 

[Paperdoc]

This is a great idea!

Even enable Bluetooth on the phone & see if you can find it with another device. I think I'll check out my microwave oven leakage detector with this to see if there is any correlation.

Maybe there should be a ATOT post your results here thread?????? With the wifi or Bluetooth test???

Sorry, I cannot agree. OP's original question comes down to this: If the damaged microwave oven in normal operation has a minor leak in the door system, how can he / she know whether that leak is emitting enough microwave power into the room to be dangerous to people? Now, INSIDE the oven there's a Magnetron tube pumping out about 500W of power around 1 to 2 GHz frequency. The door structure is supposed to prevent leakage so well that what DOES actually leak out is "safe" - that is, probably somewhere in the range of 100 mW. I'm guessing here, and the limit may be much lower than that. BUT I guarantee you that the amount of microwave power flowing around the room from an external cell phone signal from a tower is even lower!! I know that a cell phone is allowed to put out up to 300 mW at its antenna, but the signal it receives is very much lower. Now, the test proposed is to take a phone able to work well with that signal and put it into the oven, close the door, and see if the phone can pick up the tower's signal when it is inside the shield. It does not take much of a shield to cut the tower's signal to a level the phone can't pick up. Exactly how much is that attenuation figure? Can't tell from the test. Is that much attenuation enough to cut the 500W oven signal down to acceptably low when the oven is working? Even if we can dig up the info on "acceptably low" (I was just guessing), you can't tell from this test. The only way to KNOW if a damaged oven door is safe is to use calibrated equipment that measures accurately HOW MUCH microwave power is leaking out, and that equipment should be used by someone with a certain amount of training. Just being able to prove that SOME shielding is working in not good enough.

OP, IF you could FEEL an effect on your arm as a pronounced warming (that is, more than any doubt about does it feel warm or not), the microwave power involved in the leak would be LOADS more than a safe level. It would probably be in the range of 10W or higher for you to feel it that way. At that level, other body tissues could easily be damaged, especially with prolonged exposure and frequent use of the oven. The eye's retina is the most sensitive to such damage. IF you had enough power leaking to damage your retinas, you would not realize it until there was substantial and possibly permanent damage!

 

[microwaveguru]

You would not feel the leakage from a microwave oven - it is too small to generate enough heat, and the air and blood circulation dissipates all the heat. In the late 1960's, in order to demonstrate the safety of a large industrial microwave system (there were no home microwave ovens at that time), I put my hand into a microwave system that had about 10 kilowatts of power - at least 10 times what is INSIDE your oven - I felt my hand getting warm - when it started to feel hot I pulled out my hand - NO DAMAGE. What leaks from a microwave oven is at least 1 million times less than that. So, DON"T WORRY!

 

[PsiStar]

Sorry, I cannot agree.

Do you even know what Bluetooth is?

 

[TheNiceGuy]

Wow! Are you serious? Why all the concern about shielding then? All urban myth? Why aren't MWs used for things like heating people then?
If this is true, then I definitely don't need to worry. I could even have a hole in the case and it wouldn't matter.

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You would not feel the leakage from a microwave oven - it is too small to generate enough heat, and the air and blood circulation dissipates all the heat. In the late 1960's, in order to demonstrate the safety of a large industrial microwave system (there were no home microwave ovens at that time), I put my hand into a microwave system that had about 10 kilowatts of power - at least 10 times what is INSIDE your oven - I felt my hand getting warm - when it started to feel hot I pulled out my hand - NO DAMAGE. What leaks from a microwave oven is at least 1 million times less than that. So, DON"T WORRY!


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[Paperdoc]

Do you even know what Bluetooth is?

I use bluetooth every day in my hands-free cell phone system in my car.

My point is that a test was proposed which I have NO doubt will demonstrate that a phone placed inside a microwave oven with the door closed will NOT receive a signal from outside (standard cell phone signals OR bluetooth) strong enough to be received and used. However, this does NOT establish just exactly how much attenuation of RF fields is being provided by the oven case. What is the attenuation in dB? Nobody can tell from such a test. NOW, also we need to know what is the attenuation REQUIRED in an oven case / door system to ensure that the leakage from the internal power to exterior is less than the maximum allowed. Nobody here has quoted that number. Nobody here has quoted what power level, in mW or microwatts, is allowed by current safety standards to leak from domestic ovens. And that is what OP needs. He / she wants to know how to test whether the leakage actually happening from a damaged door is below maximum safe levels. The only way to answer that is to use calibrated equipment to do the measurement on the damaged oven.

 

[bobsmith1492]

The legal leakage from an oven is either 1W or 5W if I recall. That's comparable to the legal limits in the ISM band (2.4GHz), 1W spread or +10dBm CW (1/10W).

 

[Modelworks]

The calling a phone inside a microwave to prove the microwave doesn't leak is an urban myth. Plenty of perfectly safe ovens will still allow the phone to ring. If you look at the design of a microwave oven there are several points inside the cavity that microwaves can leak out. One of them is where the turntable motor connects . Those usually connect with plastic and pass through a 1/2" hole in the bottom of the cavity , plenty big enough for waves to leak out. It isn't a problem though because of the orientation of the magnetron and the fact the bottom of the outer casing is solid metal.

Remember when they leakage test an oven it is when it is fully assembled and not modified in any way. Altering door hings, switches, turntable parts or running it without the cover on and you are setting yourself up for problems.


The legal leakage used to be close to 1W but is now below 250 mw.

Metal in a microwave is not bad if done correctly. It should not touch the sides and it should not have sharp points. Some microwaves are sold with metal racks that connect to plastic anchors on the sides . Cookbooks recommend using aluminum foil over things like wing tips on chicken when defrosting to keep from cooking those parts. Microwave popcorn and all those other microwave dinners use metal to heat the popcorn. It is all in how you implement it.

 

[TheNiceGuy]

Thanks! Still not sure why the metal is dangerous.

And re the leak, I think I was just being paranoid. The front glass was smashed out, and the front cage dented, very slightly. None of the holes were breached, and the door fits as usual. I imagine the front glass is just cosmetic, so no worries, right?

Funny, it reminds me of this smart ass giving us a tour of the USS Abraham Lincoln, and he stopped in front of the reactor area door on purpose.

 

[PsiStar]

No. The glass is not cosmetic. Throw that piece of crap away.

 

[Paperdoc]

^+1 for PsiStar. Get rid of it! The risk is unknowable,and the consequences of continuing to use are potentially substantial damage you will not detect until too late.