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Thread: Microwave oven testing?
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12-31-2007, 02:54 PM #1
Microwave oven testing?
Is there a standardized method for testing a microwave oven for proper function?
Or what do you do to ensure unit is functioning properly?
The reason I ask is AHS is refusing another clients request for repairs.
Similar Threads:badair http://www.adairinspection.com Garland, TX 75042
Commercial-Residential-Construction-EIFS-Stucco-ACMV-Infrared Thermography
life is the random lottery of events followed by numerous narrow escapes...accept the good
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12-31-2007, 03:11 PM #2
Re: Microwave oven testing?
It Might have Choked Artie But it ain't gone'a choke Stymie! Our Gang " The Pooch " (1932)
Billy J. Stephens HI Service Memphis TN.
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12-31-2007, 03:43 PM #3
Re: Microwave oven testing?
Barry,
I follow what I learned from a 20+ HI veteran in Houston:
Timer & Clock: Functioning? Y/N (actually an additional item not required)
MWave: Small glass of water, heat/run for 60 seconds, if water is boiling it is functional.
Carousel: Turns? Y/N
Then there are the Range Hood options, but that is a different section of the 7A-0 form, but I do refer one to the other.
As noted above ... for built-in units only. I don't touch the portable units.
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12-31-2007, 04:02 PM #4
Re: Microwave oven testing?
Barry, I don't know of a specific test, but the boiling water is mentioned in the TREC standards as an option.
(f) Microwave oven. The inspector shall:
(1) report as in need of repair any broken or missing knobs, handles, glass panels, or other parts, or a unit that is not securely mounted;
(2) report as in need of repair any deficiencies in the door and seal (the inspector is not required to test for radiation);
(3) report as in need of repair an oven that does not operate by heating a container of water or with other test equipment, as reasonably determined by the inspector; and
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12-31-2007, 06:30 PM #5
Re: Microwave oven testing?
I carried a microwaveable hard plastic drinking cup which I would fill with water, set the timer to 30 seconds, and if the water was not 'hot to the touch', it was 'not working'. Depending on how large or small a cup you use, the water will likely boil in less than 60 seconds - I found that with the size cup I used, 30 seconds would make it 'hot to the touch'.
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01-01-2008, 07:55 AM #6
Re: Microwave oven testing?
I've always said a cup of tap water for 1 minute at high should be at least 120°F otherwise just wait for the sink supply in most homes.
I also carry microwave popcorn and will pop a bag for function and snacking on vacant properties and will ask permission on occupied, when clients are around, they like the treat and proof their future micro is working.
The issue on this one instance is a $900.00 unit that requires repair or replacement IMO and the warranty co. does not want to honor their agreement, go figure.
I was just curious what test methods were used by others.
Warranty co. says, "Inspector's 1 minute test along with a light tester is inferior and should be tested on high for 2 1/2 minutes this should boil water 212°F in most units."
Unit in question will only get to 200°F by their own time and test,
"but that is close enough" they say.
Glad I don't have to eat their cooking
Found this wattage formula but doubt it's any better than what I/we try to do during an inspection How to Easily Test Your Microwave Oven's Wattage
I'm with Jim on the boiling thing, injury or too messy on previous occasions
I'll be sticking to the 1 minute and light tester or popcorn until shown different
HNY BTW and thanks for your replies
badair http://www.adairinspection.com Garland, TX 75042
Commercial-Residential-Construction-EIFS-Stucco-ACMV-Infrared Thermography
life is the random lottery of events followed by numerous narrow escapes...accept the good
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01-01-2008, 08:15 AM #7
Re: Microwave oven testing?
Barry,
I also do the test with a cup. I use the regulation sized sippy cup, nothing fancy.
Fill the small cup and turn on for 1 minute. If water is hot to touch, I note on report that a cup of water was heated after 1 minute test.
I also check to make sure the turntable is operable and that the unit is properly supported. Check to make sure there is no damages to the door or the glass panel.
Another thing I do is make sure that the recirculating fan is venting properly. Many of these have had to fan cover panel removed as if they are going to be vented to the exterior; but many I have found vent to the bottom of the above cabinet.
I also make note if the bottom surface light is not operable and the condition of the filters.
rick
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01-01-2008, 08:59 AM #8
Re: Microwave oven testing?
I guess it goes without saying to check the receptacle the microwave is plugged into - I have found quite a few that are improperly wired, when the rest of the receptacles in the kitchen were ok.
Last edited by John Arnold; 01-01-2008 at 09:00 AM. Reason: editing
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01-01-2008, 09:47 AM #9
Re: Microwave oven testing?
I use the wet paper towel method. Wet the paper towel put it in the center and turn the unit on for about 15 seconds. That is all it takes for a nice steaming paper towel.
In my report I tell how I tested the microwave and that the only thing I can tell them is that it worked well enough to make the paper towel steam. I write in the report that I did not cook anything in it to test it.
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01-01-2008, 10:19 AM #10
Re: Microwave oven testing?
Their 'standard' is likely for their 'new' units. That may be how they selectively test their units heating capability off the assembly line. Not real scientific like the QA tests I did at a defense plant I worked at for 5 years after high school, but, then, this is not trying to guide airplanes at 500 mph at 50 above the ground either . Their test will demonstrate that the 'unit is working to their specification', presuming that is representative of their specification, of course.
Now, to the link you provided:
"Keep in mind that it’s normal for a microwave to produce less energy as it ages (hmmm… sounds familiar somehow!), but your results should be within about 50-75 watts of the rating."
I'd guess that the 12 degrees difference is within or close to that "50-75 watts of the rating".
By the way, the stuff I worked on was with microwaves, only very few of our tubes were in that low wattage range. We even had a few in the <1 watt (rated in mW) range, but most were in the kW to MW range (some I tested were over 5 mega watts). Nonetheless, though, there is a reduction in power over time (aging effect) as stated in your link.
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01-01-2008, 10:33 AM #11
Re: Microwave oven testing?
Warranty co. says, "Inspector's 1 minute test along with a light tester is inferior and should be tested on high for 2 1/2 minutes this should boil water 212°F in most units."
Unit in question will only get to 200°F by their own time and test,
"but that is close enough" they say.
That would also be something to consider when testing to a specific temperature over a certain time; 40 degree water takes longer to reach boiling than 80 degree water.
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01-01-2008, 02:27 PM #12
Re: Microwave oven testing?
Does, did or will the warranty company provide documentation for their testing procedures? It would be nice to see what that basis is.
I don't think any of the various SOPs get to this level of data collection for a microwave.
I know that isn't the bottom line here as you are working with a client to help resolve an issue and are being taken to task for more definitive information.
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01-01-2008, 08:04 PM #13
Re: Microwave oven testing?
I basically do all the same as stated above:
check seal
turntable
light
temp w/ sippy cup of agui for 1x min-- s/b 110-120F
CHECK FOR RUST!!! Any rust is necessitates hitting it with a baseball bat.
I do not check units not permanent to the structure (built-in).
Dick
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01-02-2008, 01:15 PM #14
Re: Microwave oven testing?
I use the paper towel method too.
NOTE!! Do NOT put a "dry" fabric shop towel in for the test. It WILL catch fire - yes flames and a lot of nasty smelling smoke. Not that it ever happened to me....no, and that's my story.
I check the control panel to see if the buttons work.
The light and turntable.
If it heats up my paper towel to steam.
"Inspector's 1 minute test along with a light tester is inferior and should be tested on high for 2 1/2 minutes this should boil water 212°F in most units."
Unit in question will only get to 200°F by their own time and test,
"but that is close enough" they say."
They may have a point. The cheapo microwave in my basement takes much longer to make popcorn compared to the one in the kitchen. I think the power rating has a lot to do with it. If it boils water in a reasonable amount of time, I would have to say it is probably OK.
When I make press coffee (in the good kitchen one), I put 16 oz of water (room temp) and hit 3 minutes and it boils just before the timer goes off. And it's a full rolling boil by then (220 degrees).
I have found that if I use the water from my refrigerator door, it just about the same time.
JF
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01-02-2008, 03:43 PM #15
Re: Microwave oven testing?
Why any paper towel at all? Why put anything combustible at all in a micowave? Show me the light.
rick
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01-02-2008, 05:04 PM #16
Re: Microwave oven testing?
Rick,
It's wet not damp. Most always on site. one less thing in the bag.
Push 33 start it steams that part of testing is done.(Don't Walk away).
1.Dish Washer
2.Set Oven 350
3. Set Burners on Low
Snatch a couple of paper towels (wet and leave water running.)
Press 33 start.(Light comes on?,Table turning?
Open cabinet under sink (Drain Leaking?)
Microwave timer dings. Steam = Microwave,Seal?Cabinet?Test other Buttons,
Back to Drain. ect.
Everybody has their own way.
It Might have Choked Artie But it ain't gone'a choke Stymie! Our Gang " The Pooch " (1932)
Billy J. Stephens HI Service Memphis TN.
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01-02-2008, 06:11 PM #17
Re: Microwave oven testing?
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01-02-2008, 09:21 PM #18
Re: Microwave oven testing?
Generally speaking: the temperature at which boiling occurs (boiling point) depends upon pressure. At sea level (14.7 psia or 0 psig), yes water boils at 212 degrees. On a mountain in Colorado it will boil at a lower temperature. A lot of cook books have "high altitude" instructions to adjust recipes for this lower boiling temperature. Water will boil at higher temperatures when under pressure (hence the use of the "pressure cooker") and on a submarine (I believe they do allow the air pressure to increase somewhat above normal atmospheric when submerged).
When it begins boiling, liquid water will continue to boil at the same temperature (dictated by the pressure). As more heat is applied the rate of boiling increases but the temperature remains the same. The steam will be at a much higher temperature than the boiling water.
However there is also a special case called superheating. A liquid can be heated to a temperature significantly above it's normal boiling point if it is heated in a smooth walled container and kept very still. This prevents those little bubbles from forming in the water (called nucleation) and delays the onset of boiling. When being superheated, the water is storing energy that will be released in a steam explosion accompanied with rapid boiling if the water is disturbed.
Superheating is a concern when using microwave ovens to boil water, especially those units without turntables. Opening the door, setting the cup down on the counter, dropping a tea bag or a spoon of sugar into it ... any of these could kick off the boiling process and send scalding water flying. Many people have gotten severe burns from this.
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01-02-2008, 09:29 PM #19
Re: Microwave oven testing?
Yes, I was referencing the sea level boiling point as Jack stated 212 degrees.
Water will boil at higher temperatures when under pressure (hence the use of the "pressure cooker") ...
When it begins boiling, liquid water will continue to boil at the same temperature (dictated by the pressure). As more heat is applied the rate of boiling increases but the temperature remains the same. The steam will be at a much higher temperature than the boiling water.
However there is also a special case called superheating. A liquid can be heated to a temperature significantly above it's normal boiling point if it is heated in a smooth walled container and kept very still. This prevents those little bubbles from forming in the water (called nucleation) and delays the onset of boiling. When being superheated, the water is storing energy that will be released in a steam explosion accompanied with rapid boiling if the water is disturbed.
Superheating is a concern when using microwave ovens to boil water, especially those units without turntables. Opening the door, setting the cup down on the counter, dropping a tea bag or a spoon of sugar into it ... any of these could kick off the boiling process and send scalding water flying. Many people have gotten severe burns from this.
Last edited by Jerry Peck; 01-03-2008 at 06:29 PM. Reason: had 121 instead of 212 degrees
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01-03-2008, 08:26 AM #20
Re: Microwave oven testing?
At a home the other day, when I opened the microwave there was already a cup of water in the unit.
I asked the homeowner if she was going to warm it up for coffee. She told me no that it was there to catch the micowave "thingies".
After the WTF look I gave her, she told me that she had been told by a lab professor years ago that the water help catch any of the bouncing microwaves still left in the oven when it was turned off.
She said she had been doing this for about 25 years now.
This also explained why the tennis balls where hanging down from the ceiling in the garage.
rick
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01-03-2008, 02:16 PM #21
Re: Microwave oven testing?
Sorry Jerry - hit the wrong keys. I know that's never happened here before.
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01-03-2008, 06:31 PM #22
Re: Microwave oven testing?
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01-03-2008, 09:01 PM #23
Re: Microwave oven testing?
The scientific data has came in.
rick
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01-04-2008, 04:28 AM #24
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01-04-2008, 10:51 AM #25
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04-06-2009, 07:08 AM #26
Re: Microwave oven testing?
One more thought on this subject: It's been rumored that superheated water in a microwave environment can actually rise above the boiling point without visibly boiling. When removing container from the interior, it may feel cool to the touch, but the water then explodes when disturbed.
I have not personally experienced this, but have found some validity to this claim while searching the internet.
Just something of which to be aware.
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04-06-2009, 07:22 AM #27
Re: Microwave oven testing?
I have grabbed many an iterm from microwaves and at first grab they are not hot at all and by the time you get to the counter your fingers are frying.
Only in the microwave. Things on stoves or in ovens are just blister material. You don't have to wait to feel the heat.
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04-06-2009, 08:11 AM #28
Re: Microwave oven testing?
That's because, in a regular oven, the container is heated first, then the heat works its way through to the stuff in the container, while in a microwave oven the stuff in the container heats first, then the heat works it way through to the container.
With a microwave oven you are standing there waiting for the seconds to tick off so you can take out whatever you were trying to heat in a hurry, and you pick the container up with limited heating of it, but by the time you get it to the counter - Yikes! I should have used a pot holder! - nothing mysterious about that.
Regarding the water boiling thing? I seriously doubt it as the difference would be pressure, not heat, and the inside of the microwave is essentially at the same air pressure as the outside-the-microwave air pressure is. However, if you heated the water to just-below-boiling, opened the door and reached for it, the residual heat of the moment before could now have caused the water to reach boiling, but it is not going to explode when disturbed. I think it would be related to the heating of the container - if the container is not yet hot, it will not boil as heat is being lost to the container, however, if at that precise moment in time the container heated, then the last heat applied would be held in the container and would finish heating the water to boiling, but again, not exploding when disturbed.
It would take some convincing arguments and data to make my believe that happens.
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04-06-2009, 10:22 AM #29
Re: Microwave oven testing?
This is from a user manual for GE Microwave:
SUPERHEATED WATER
Liquids, such as water,
coffee or tea are able to be
overheated beyond the
boiling point without
appearing to be boiling.
Visible bubbling or boiling
when the container is
removed from the microwave
oven is not always present.
THIS COULD RESULT IN VERY
HOT LIQUIDS SUDDENLY
BOILING OVER WHEN THE
CONTAINER IS DISTURBED
OR A SPOON OR OTHER
UTENSIL IS INSERTED INTO
THE LIQUID.
To reduce the risk of injury
to persons:
— Do not overheat the liquid.
— Stir the liquid both before
and halfway through
heating it.
— Do not use straight-sided
containers with narrow
necks.
— After heating, allow the
container to stand in the
microwave oven for a short
time before removing the
container.
— Use extreme care when
inserting a spoon or other
utensil into the container.
try this Jerry (no, no, Don't TRY this) just see if this from GE persuades you.
snopes.com: Superheated Microwaved Water
Or this from Snopes
Here is a brief explanation:As well as heating up everything from breakfast noodles to nightcaps, each of these tens of millions of microwave ovens can "superheat" a cup of water, and if you are very unlucky, toss it into your face.
You would expect that "boiling point" is straight-forward — it's the temperature at which a liquid boils and turns into a gas.
But "superheating" is a strange phenomenon in which a liquid can be heated to above its boiling point. For example, water can be heated to 101°C, and still remain a liquid and not turn into steam.
Liquid water will become steam at 100°C, if there already is a tiny bubble of anything (air, steam) present. But if there is no such bubble present, then the liquid will need to be heated to over 100°C to get enough energy to make that first bubble.
A typical disaster scenario has the unwitting person first filling a cup with water — a cup with a very smooth internal surface.
A surface with tiny scratches has a myriad of hiding spots for bubbles, but a smooth surface does not. They place this very smooth bubble-free cup into their nuker, which heats the water to 101°C.
This superheated water is like a cocked gun, needing only a small "trigger" to set it off. The trigger can be the addition of a tea bag, instant coffee powder or sugar, each of which will carry bubbles into the superheated water.
The trigger can even be the shock wave from moving or bumping the cup of superheated water.
Your typical cup of tea has a volume of about 100ml, roughly the volume of a tennis ball. In your typical 100ml of superheated water in a cup, 0.2ml (about the volume of a big match head) will turn into 300ml of steam.
If that "match head" of water is on the surface, it will turn into a small puff of steam. But if that 0.2ml volume of water is near the bottom of the cup, it will push all the water above it out of the cup.
If you happen to be bending closely over the cup, you can get a faceful of hot water.
It's easy to avoid. Don't heat the water in your microwave for too long. Use an old cup with a few scratches. Have a non-metal object, like a wooden spoon or a stirring stick, sitting in the heating liquid — its furry surface will trap lots of bubbles.
Before you remove the cup from the nuker, tap its side from a safe distance with a long object. And as always with hot water, keep your face and body at a safe distance.
Last edited by Jim Luttrall; 04-06-2009 at 10:38 AM.
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04-06-2009, 10:43 AM #30
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04-06-2009, 10:48 AM #31
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04-06-2009, 10:50 AM #32
Re: Microwave oven testing?
I use a cheap red plastic cup half filled with water, set it on high for 3 minutes and let it rip. When it's finished I open the door and point my IR thermometer at it and record the temperature. I leave the cup in the oven so as not to get burned.
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04-06-2009, 11:18 AM #33
Re: Microwave oven testing?
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04-06-2009, 12:13 PM #34
Re: Microwave oven testing?
I've always used one cup of measured tap water in a vintage two-cup Pyrex (R) measuring cup.
Plastics can melt. Too much plastic and decorated items from overseas contain metals, especially lead, remember the recalls and even pvc blinds from china and mexico.
I have always used this method. Otherwise avoiding trouble from home owners or purchasers with issues about "contaminating" their microwave and/or home with plastic fumes, lead, other toxins and avoiding the melted plastic rupturing, somthing else breaking, and flooding installed microwave or microhood.
Note: I've heard that modern Pyrex (R) is reformulated, not made here anymore, and not as chip resistant/strong as the vintage but haven't looked into that to verify, so it might not be the case.
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04-06-2009, 01:12 PM #35
Re: Microwave oven testing?
All Pyrex or subtance as such is slowly leaving the US and going over seas.
You can buy a coated 16 inch newtonian telescope mirror from over seas (and a pretty darn goon one) for 12 to 1500. In the US the price is anywhere from 2800 to 4000. The 2800 is probably to cheap a quote.
Machine manufacturing and testing and coating and shipping from overseas is half or less the cost. Again this is for a fairly high quality mirror. Pyrex blanks for mirrors are almost impossible to get in the states for any size of 16 inches or over.
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04-06-2009, 01:30 PM #36
Re: Microwave oven testing?
I find that the hamster "pop" method works the best. If the hamster pops within 20 seconds of the unit being on high then the oven is working!
Seriously, I use a wet paper towel. If it steams in about 15 seconds then I say it is working. I also have one of those fancy plastic bars with LED lights that flash as the magnetron tube turns on and off. It is a good toy that the clients love to see and Oooh and Ahhhh over.
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04-06-2009, 01:42 PM #37
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04-06-2009, 02:44 PM #38
Re: Microwave oven testing?
I used to use a leagage detector until it broke. The problem was there was noy way to determine what exactly a "high" indication meant and by who's standards. Go Figure.
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04-06-2009, 03:23 PM #39
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04-06-2009, 11:26 PM #40
Re: Microwave oven testing?
I use a "UEI" Model MW1A radiation leak tester too. (It is about $50 each. I have a working tester, and keep a brand new in my trunk in case for calibration.)
I put in a plastic cup of tap water, set at high power level for 1/2 minute. Check any radiation leak along seam of oven door when it is in operation. Then check the cup is hot/warm or not. (I don't measure the temperature of the heated water, because it depends on the maximum output of oven.)
Then I report, Operational microwave oven, no significant microwave leaking as tested by a "UEI" leak tester Model MW1A.
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04-07-2009, 02:52 AM #41
Re: Microwave oven testing?
You might try telling agents and sellers (maybe even cloying buyers) to look for the microwave leakage themselves. This will quell the depression they are experiencing due to having been pried away from reality TV long enough to try to delve into the mystery of why you are not being interrupted by commercials.
Put the proverbial (preferably large) cup of water inside the oven; set the machine on high, and shut off the lights in the kitchen. Tell them it takes about 20 minutes or so for the leakage to appear as little, almost imperceptible red and blue sparks around the edges of the door.
You can now go about your work undeterred.
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04-13-2009, 09:02 AM #42
Re: Microwave oven testing?
Good morning, Gents-
I used to do a lot of microwave testing in homes, but nowadays, with microwave being so inexpensive, it is actually cheaper for someone to buy a new one than hire me to test their existing one.
But just a quick point, contrary to what has been stated here on the board, there are emission standards and limits and there is a standard microwave testing protocol.
You can find that located in the Code of Federal Regulations, Title 21 Part 1030
Cheers!
Caoimh*n P. Connell
Forensic Industrial Hygienist
Forensic Industrial Hygiene
(The opinions expressed here are exclusively my personal opinions and do not necessarily reflect my professional opinion, opinion of my employer, agency, peers, or professional affiliates. The above post is for information only and does not reflect professional advice and is not intended to supercede the professional advice of others.)
AMDG
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04-19-2009, 11:29 PM #43
Re: Microwave oven testing?
Does anyone use the clearplastic microwave testers ?? Do they work??
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04-21-2009, 06:21 AM #44
Re: Microwave oven testing?
I'm not familiar with the device - could you provide a little more info on them?
CPC
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04-21-2009, 01:07 PM #45
Re: Microwave oven testing?
"The Code is not a peak to reach but a foundation to build from."
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04-21-2009, 01:21 PM #46
Re: Microwave oven testing?
This is what I use
MD200 Microwave Leakage Detector
edit here
Amazing how micro wave checking gets 2000 views and 50 replies. Just curious
Last edited by Ted Menelly; 04-21-2009 at 01:36 PM.
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04-21-2009, 08:15 PM #47
Re: Microwave oven testing?
Bruce Thompson, Lic. #9199
www.TylerHomeInspector.com
Home Inspections in the Tyler and East Texas area
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04-22-2009, 04:44 PM #48
Re: Microwave oven testing?
Hi Gents –
I have a confession. I have a bit of a mischievous streak. Over the years, I have given family members “explanations” of various things that are less than – well – accurate.
For example our daughter, an otherwise intelligent lass, now pushing 22 years old, recently had her boyfriend over for dinner. Somehow the conversation turned to hardware and tools, and in particular levels. My daughter let slip a bit of knowledge gained from her old Dad many years ago that the bubble in a spirit level was actually a fish fart, and the best quality levels used goldfish farts, because they were more stable.
I don’t know how we managed to keep the boyfriend from choking with laughter.
My daughter is still making discoveries about some of my explanations on how the world operates.
Cheers!
Caoimh*n P. Connell
Forensic Industrial Hygienist
Forensic Industrial Hygiene
(The opinions expressed here are exclusively my personal opinions and do not necessarily reflect my professional opinion, opinion of my employer, agency, peers, or professional affiliates. The above post is for information only and does not reflect professional advice and is not intended to supercede the professional advice of others.)
AMDG
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04-22-2009, 05:08 PM #49
Re: Microwave oven testing?
I use to play that game a lot when my kids were little.
One that struck me a several years ago when one of my daughters was in a conversation about presidents with some friends. When they were talking about interesting things about presidents my daughter comes out with President Johnsons wives son from a first marriage. They all told her that Johnsons wife was not married before. My daughter said to them " Why do you think they call her lady bird and has a son called Larry Bird the basket ball player.
Needless to say they all busted out and put her into serious embarrassment because old dad just mentioned it out of the blue once when she was a young girl in elementary school and she just found out it was one of my complete bull comments. I used to say them so seriously she never had a reason not to believe me. What would kids do without pain in the ass dads.
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