easy way to generate an ac signal

This is what I actually said (Quote)

All rotating electric machines run on AC. All can be used as a "motor" or "generator".

(Unquote)

Perhaps you are. Pretty good at moving the goal posts though.

Just as electronic devices are not capable of producing an exact sine wave, rotating mechanical generators can't produce an exact square wave.

Citation? The only way you will get a pure sine wave is from a vibrating string or similar.

Oh dont be silly harry. We;ve been making variable frequency sine wave oscillators with better than 0.01% THD for YEARS.

If you want better than that simply bang them, through a nth order low pass filter

These days with digits, you can do even better with the right DAC and filters.

You've got absolutely *no* chance of getting a pure sine wave from a vibrating string. Mostly, you get a distorted sawtooth waveform. The closest thing to a sinewave generated by non-electrical means is the sound of a flute,and even that has noticeable harmonic content. Even the mains is closer than most mechanical sine wave generators.

Electronic sine waves are *much* closer to perfect than mechanically generated ones, and not even electronic units can produce a perfect square wave. I suggest you spend some quality time with a decent oscilloscope and some signal generators. While you're at it, maybe you'd like to take a picture of the waveform generated by the stator of a car alternator and show us. Then take a snap of the "perfect" sine wave you claim to get from a vibrating string, preferably using a spectrum analyser..

One here is somewhere around .0005% but the measurement becomes a bit uncertain around that level;!...

Which is an integral part of the *motor*. The *motor* runs on DC, what it does internally is of no concern.

MBQ

I can't better either you or the dogging comparison for comedy value.

MBQ

And your point is?

Yeah, right.

MBQ

What you also actually said:

(Quote) "The rotating part of any electrical machine caries AC." (Unquote)

- Harry 27th October

It's even included in the quoted text.

MBQ

No moved goalposts, just another request of evidence to show your claims.

Could you possibly do a bit of snipping rather than re-posting the entire thread for your one liner?

Oh? And how doyou determine how "perfect" a sine wave is?

I do it by comparing the shape of the curve generated, considered as the changes in voltage or displacement, along the time axis with a sine function plotted on the same basis to a scale which produces the same peak heights. How would you do it?

If it's electrical, I use a spectrum analyser to check what frequencies are there, and at what amplitude. This then gives me a figure for the distortion of the waveform. If it's really grotty, I just look at it on an oscilloscope display.

I use a distortion meter or a spectrum analyser if I have one handy

An electronic way to do the same thing. But I was asking Harry. I doubt he'd (a) know what one is, and (b) know how to connect it.

When I was at school, we worked out a way to see the shape of the vibrating string at various points in its vibration using a strobe. We had a good physics lab. If you did it right, you could just about see the non-sine bits of the shape. The microphone on the oscilloscope told the same story.

Very similar to the way you determine how "imperfect" it is.

MBQ