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Inaccurate Clock on Microwave Oven


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Has anyone noticed that their microwave ovens' clock can be inaccurate sometimes?

 

I've noticed this on the two different microwave ovens in my house. One is a Sunbeam brand (newer model) and the other one is an older Panasonic model (about 10 years old).

 

The clocks on the microwave invariably run faster (like 5 minutes faster or more than all the other clocks in the house). I would then set the microwave clock back to the same time as the other clocks in the house but after a few days, the microwaves would then move faster again. My hypothesis is that when a microwave operates (e.g. cooking food), it generates a rotating magnetic field that could distort the time space area around it and make the clock faster.

 

I haven't done any formal scientific experiments to test this. Maybe there are some physicists who have the lab equipment to test out this theory.

 

 

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Has anyone noticed that their microwave ovens' clock can be inaccurate sometimes?

 

I've noticed this on the two different microwave ovens in my house. One is a Sunbeam brand (newer model) and the other one is an older Panasonic model (about 10 years old).

 

The clocks on the microwave invariably run faster (like 5 minutes faster or more than all the other clocks in the house). I would then set the microwave clock back to the same time as the other clocks in the house but after a few days, the microwaves would then move faster again. My hypothesis is that when a microwave operates (e.g. cooking food), it generates a rotating magnetic field that could distort the time space area around it and make the clock faster.

 

I haven't done any formal scientific experiments to test this. Maybe there are some physicists who have the lab equipment to test out this theory.

Ok I bite this one (No pun intended.) The microwave works on something called a magnetron.

 

Reference comes from http://en.wikipedia.org/wiki/Magnetron

 

All cavity magnetrons consist of a hot filament (cathode) kept at, or pulsed to, a high negative potential by a high-voltage, direct-current power supply. The cathode is built into the center of an evacuated, lobed, circular chamber. A magnetic field parallel to the filament is imposed by a permanent magnet. The magnetic field causes the electrons, attracted to the (relatively) positive outer part of the chamber, to spiral outward in a circular path rather than moving directly to this anode. Spaced around the rim of the chamber are cylindrical cavities. The cavities are open along their length and connect the common cavity space. As electrons sweep past these openings, they induce a resonant, high-frequency radio field in the cavity, which in turn causes the electrons to bunch into groups. A portion of this field is extracted with a short antenna that is connected to a waveguide (a metal tube usually of rectangular cross section). The waveguide directs the extracted RF energy to the load, which may be a cooking chamber in a microwave oven or a high-gain antenna in the case of radar.

 

The sizes of the cavities determine the resonant frequency, and thereby the frequency of emitted microwaves. However, the frequency is not precisely controllable. This is not a problem in uses such as heating, or in some forms of radar where the receiver can be synchronized with an imprecise magnetron frequency. Where precise frequencies are needed, other devices such as the klystron are used.

 

The magnetron is a fairly efficient device. In a microwave oven, for instance, a 1100 watt input will generally create about 700 watts of microwave energy, an efficiency of around 65%. (The high-voltage and the properties of the cathode determine the power of a magnetron.) Instead of a magnetron, transistors can be used to provide microwave power; transistors typically operate at around 25 to 30% efficiency. Transistors are used in roles which require a wide range and/or stable range of frequencies. Thus the magnetron, having a higher efficiency, remains in widespread use in roles which require high power, but where precise frequency control is unimportant.

 

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There is simply not enough power to distort space or time enough to effect the microwave clock. Energy can be used to distort space and time but the amount of energy needed is very great. I use my own microwave clock when I am getting around for work in the morning and have been using it for many many years. There is no time distortation at least not that can be noticed. Your going to need a lot more power to do what your talking about. Also, electrons have a magnetic field but there is also a permanent magnet there. I don,t think there is enough of a spinning magnetic field with enough energy to do what your talking about.

 

 

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Reactor,

 

Good reference on the magnetron.

 

If a household .7 kW magnetron could somehow cause close-by clocks to desynchronize by five minutes via spacetime distortion in (he didn't say how long it takes but let's just plug in 1 month), imagine how de-synchronized a Navy DDG or Frigate would become desynchronized with the rest of the world when they activated their 1/2 megawatt radar klystron (which is just a large magnetron)...or when SLAC activates its 50 megawatt linear particle accelerator (which is a much larger klystron). CERN's LHC accelerator, with its output of 180 megawatts, wouldn't have to be concerned with making black holes. It would be a time machine all by itself once activated.

 

The entire sun, with all of its mass and electromagnetic energy, only manages to distort spacetime such that a photon that passes it at grazing incidence has its path altered by just 1.7 seconds of arc.

 

But...

 

Backto1992,

 

There's nothing wrong with doing experiments. First thing's first. A set of two microwaves is an insignificant test population. I'd determine the general accuracy of all new clocks installed in microwave ovens. Next I'd determine what effects microwave energy has on the solid state components of the same clocks and what is considered adequate shielding for the clocks to maintain their base accuracy absent microwave energy. I'd also be interested in knowning the mean time to failure of microwave clocks and the profile of how they break down over time in the presence of microwave energy (say over the ten year period of the Panasonic oven). The last thing that I would try to find are any and all sources of "noise" in my laboratory setting - noise being anything that introduces effects unto my experiment from the outside world that actually are not a part of my set-up. I want to completely isolate, as best as I can, my apparatus from the outside world and its input. Practically speaking we're talking about experimental results that have to be calculated to 7 decimal points of accuracy. Otherwise a mouse farting in the next room can introduce noise into the results.

 

That gives you a set of criteria for building the degree of uncertainty of the accuracy of the clocks into the experiment under both conditions: microwaves present +shielding; microwaves absent. Now you can run experiments with microwave oven clocks to see if there really is an inaccuracy that is otherwise unexpected (statistical modelling that includes uncertainty as compared to experimental results).

 

OK - now you testbed as many microwave ovens as you can find.

 

 

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you all missed the obvious, it's not swiss movement

Precisely why wanted to know the general accuracy of clocks placed in microwave ovens. No one is going to pay a premium for a clock on a machine that cooks food given that 3-4 seconds one way or the other over the course of 5 minute cook time is close enough. Of course the clocks are much more accirate than that but they are the cheapest clock available for the particular product given the required accuracy for what he gadget was designed for.

 

 

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Precisely why wanted to know the general accuracy of clocks placed in microwave ovens. No one is going to pay a premium for a clock on a machine that cooks food given that 3-4 seconds one way or the other over the course of 5 minute cook time is close enough. Of course the clocks are much more accirate than that but they are the cheapest clock available for the particular product given the required accuracy for what he gadget was designed for.

Preccisely. I have to reset mine once in a while mainly do to power outages more than the clock being off. Anyway my microwave clock does a good job keeping time and it is a fairly old outdated microwave.

 

 

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My theory is that rotating magnetic fields mess with electronic devices such as digital clocks.

Correct. A rotating magnetic field will have an associated rotating electric field oriented at 90 degrees to the magnetic field. That's how a generator works.

 

Without proper shielding it will affect other electronic devices like digital timers.

 

 

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