Terminology

You may have seen me rail against how the schools teach that inversion is t he same thing as 180 degrees out. Out of phase, by definition or etymology or whatever the f*ck at least strongly implies that THIS signal is THAT sig

Now, these two waveforms, say applied to a CRO (and ALWAYS own a CRO as lon g as you shall live) and syncing, they look the same as long as they are sy mmetrical. But we have two types of symmetrical.

Consider:

/\/\/\/\/\/\/\/\/\/\/\/\

And:

/|/|/|/|/|/|/|/|/|/|/|/|/|

Or as my Wavtek will put out:

/|_/|_/|_/|_/|_/|_/|_/|_/|

With a dead time that is half the sawtooth wave.

Now, we should all know this, it is not that hard of a concept. But how is it expressed ?

If I was the word chooser of the world, a sawtooth wave would be called "Sy mmetrical in period" but NOT "Symmetrical in polarity".

What are the proper terms for that ?

Reply to
jurb6006
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Inversion symmetry and translation symmetry?

Jeroen Belleman

Reply to
Jeroen Belleman

I would say an offset sawtooth. Or a sawtooth with DC component.

Try the "inversion" with a asymetrical signal and see the result, though it is periodic.

Exemple : MMMM.... delayed by half a period gives MMMM..... ; try to invert it ! (something like WWWW).

On a scope, you would see the same trace since it is triggered even with a dual-channel.

Sorry for my "French English" !

Reply to
Look165

Periodic waves all have translational symmetry in the time dimension

The first two have glide reflection symmetry, and also mirror symmetry (at any peak or trough) and rotatinal symmetery (about any zero-crossing)

the last has, only translational symmetrty in the time dimension the second last has in addition the rotational symmetry

this (square wave through low-pass filter) has glide reflection (on time and voltage) but not time refelction. or rotation _ _ _ _ _ _ _ _ _ / | / | / | / | / | / | / | / | / | | \_| \_| \_| \_| \_| \_| \_| \_| \

This (uneven square wave) has time reflectional symmetry on time but not glide reflection or rotatiom _ _ _ _ _ _ _ _ _ __| |___| |___| |___| |___| |___| |___| |___| |___| |__

--
  When I tried casting out nines I made a hash of it.
Reply to
Jasen Betts

We use "symmetric" to mean flippable on the vertical axis, amplitude.

The concept of "time reversal" is pretty rarely discussed, so we say that when we mean it.

CRO? Those funny old things with electron guns and deflection plates? Haven't use one in a decade or two.

--
John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
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Reply to
John Larkin

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