Mad Prof wrote:> The bit about whether it is + or -180 degrees. > > Well if you design a positive 180 degrees circuit (that has no amplitude > variations). I would use it as a phase advance in every servo in the world. > ie if we had a phase margin of -5degrees and we put your circuit in then it > would be perfectly stable with a phase margin of +180-5 degrees! The fact > that an inverter would make things worse is testament to the fact that it > has to be -180 degrees phase shift. > > > M.P > > "Jerry Avins" <jya@ieee.org> wrote in message > news:mMCdnbE7gOsqTQzZnZ2dnUVZ_rKdnZ2d@rcn.net... >> For a pure sinusoid, the effects of an inverter and of a 180 degree >> phase shift are indistinguishable. I lay the burden upon anyone who >> maintains that "indistinguishable" means "the same thing" to explain >> whether the phase shift is positive or negative, and to reconcile the >> behavior of transients in inverters and diode ring modulators. >> >> I apologize to all who may believe that this is a troll. It may be >> indistinguishable, but it's not the same thing. :-)How do you know by looking at the waveform? Suppose an otherwise a perfect sinusoid with a blip near the positive peak went into a <name your color> box, and emerged with the blip near the negative peak. Would you guess that there was a phase shifter in the box? My question was intended to provoke the realization that inversion is not a phase shift of any kind, even though it may sometimes be expedient to call it one. Beware: "If a tail ..." Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
How does an inverter affect phase?
Started by ●June 15, 2006
Reply by ●June 17, 20062006-06-17
Reply by ●June 17, 20062006-06-17
Jerry Avins wrote: .=2E.> My question was intended to provoke the realization that inversion is > not a phase shift of any kind, even though it may sometimes be expedient > to call it one.Now you are really trolling, aren't you? If not, then it might be interesting (shock therapy) to write down the transfer function of a) a 180=B0 phase shifter and b) an inverter. Now compare the two ...> Beware: "If a tail ..."A search for those words returns http://www.xmission.com/~emailbox/tailtalk.htm ?
Reply by ●June 17, 20062006-06-17
Andor wrote:> Jerry Avins wrote: > ... >> My question was intended to provoke the realization that inversion is >> not a phase shift of any kind, even though it may sometimes be expedient >> to call it one. > > Now you are really trolling, aren't you? If not, then it might be > interesting (shock therapy) to write down the transfer function of > > a) a 180� phase shifter > > and > > b) an inverter. > > Now compare the two ...Now compare their group delays. Transfer functions with different group delays are not identical.>> Beware: "If a tail ..."I should have written "If you call a tail ..." Lincoln is reported to have cut through a sophistic argument put forward by one of his cabinet secretaries with, "If you call a tail a leg, how many legs does a sheep have?" When the secretary answered five, he responded, "Four. Calling a tail a leg a leg doesn't make it one." Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●June 17, 20062006-06-17
Andor wrote:> Jerry Avins wrote: > ... >> My question was intended to provoke the realization that inversion is >> not a phase shift of any kind, even though it may sometimes be expedient >> to call it one. > > Now you are really trolling, aren't you? If not, then it might be > interesting (shock therapy) to write down the transfer function of > > a) a 180� phase shifter > > and > > b) an inverter. > > Now compare the two ...Now compare their group delays. Transfer functions with different group delays are not identical.>> Beware: "If a tail ..."I should have written "If you call a tail ..." Lincoln is reported to have cut through a sophistic argument put forward by one of his cabinet secretaries with, "If you call a tail a leg, how many legs does a sheep have?" When the secretary answered five, he responded, "Four. Calling a tail a leg a leg doesn't make it one." Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●June 17, 20062006-06-17
Andor wrote:> Jerry Avins wrote: > ... >> My question was intended to provoke the realization that inversion is >> not a phase shift of any kind, even though it may sometimes be expedient >> to call it one. > > Now you are really trolling, aren't you? If not, then it might be > interesting (shock therapy) to write down the transfer function of > > a) a 180� phase shifter > > and > > b) an inverter. > > Now compare the two ...Now compare their group delays. Transfer functions with different group delays are not identical.>> Beware: "If a tail ..."I should have written "If you call a tail ..." Lincoln is reported to have cut through a sophistic argument put forward by one of his cabinet secretaries with, "If you call a tail a leg, how many legs does a sheep have?" When the secretary answered five, he responded, "Four. Calling a tail a leg a leg doesn't make it one." Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●June 17, 20062006-06-17
Andor wrote:> Jerry Avins wrote: > ... >> My question was intended to provoke the realization that inversion is >> not a phase shift of any kind, even though it may sometimes be expedient >> to call it one. > > Now you are really trolling, aren't you? If not, then it might be > interesting (shock therapy) to write down the transfer function of > > a) a 180� phase shifter > > and > > b) an inverter. > > Now compare the two ...Now compare their group delays. Transfer functions with different group delays are not identical.>> Beware: "If a tail ..."I should have written "If you call a tail ..." Lincoln is reported to have cut through a sophistic argument put forward by one of his cabinet secretaries with, "If you call a tail a leg, how many legs does a sheep have?" When the secretary answered five, he responded, "Four. Calling a tail a leg a leg doesn't make it one." Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●June 17, 20062006-06-17
Andor wrote:> Jerry Avins wrote: > ... >> My question was intended to provoke the realization that inversion is >> not a phase shift of any kind, even though it may sometimes be expedient >> to call it one. > > Now you are really trolling, aren't you? If not, then it might be > interesting (shock therapy) to write down the transfer function of > > a) a 180� phase shifter > > and > > b) an inverter. > > Now compare the two ...Now compare their group delays. Transfer functions with different group delays are not identical.>> Beware: "If a tail ..."I should have written "If you call a tail ..." Lincoln is reported to have cut through a sophistic argument put forward by one of his cabinet secretaries with, "If you call a tail a leg, how many legs does a sheep have?" When the secretary answered five, he responded, "Four. Calling a tail a leg a leg doesn't make it one." Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●June 17, 20062006-06-17
Jerry Avins wrote:> ... "Calling a tail a leg a leg doesn't make it one."Calling ketchup a vegetable doesn't make it one. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●June 17, 20062006-06-17
Jerry Avins schrieb:> Andor wrote: > > Jerry Avins wrote: > > ... > >> My question was intended to provoke the realization that inversion is > >> not a phase shift of any kind, even though it may sometimes be expedie=nt> >> to call it one. > > > > Now you are really trolling, aren't you? If not, then it might be > > interesting (shock therapy) to write down the transfer function of > > > > a) a 180=B0 phase shifter > > > > and > > > > b) an inverter. > > > > Now compare the two ... > > Now compare their group delays. Transfer functions with different group > delays are not identical.But equal transfer functions have equal group delay ... did you read that post I linked regarding this exact same discussion 15 years ago in this forum?> > >> Beware: "If a tail ..." > > I should have written "If you call a tail ..." Lincoln is reported to > have cut through a sophistic argument put forward by one of his cabinet > secretaries with, "If you call a tail a leg, how many legs does a sheep > have?" When the secretary answered five, he responded, "Four. Calling a > tail a leg a leg doesn't make it one."Ok.
Reply by ●June 17, 20062006-06-17
Jerry Avins schrieb:> Andor wrote: > > Jerry Avins wrote: > > ... > >> My question was intended to provoke the realization that inversion is > >> not a phase shift of any kind, even though it may sometimes be expedie=nt> >> to call it one. > > > > Now you are really trolling, aren't you? If not, then it might be > > interesting (shock therapy) to write down the transfer function of > > > > a) a 180=B0 phase shifter > > > > and > > > > b) an inverter. > > > > Now compare the two ... > > Now compare their group delays. Transfer functions with different group > delays are not identical.But equal transfer functions have equal group delay ... did you read that post I linked regarding this exact same discussion 15 years ago in this forum?> > >> Beware: "If a tail ..." > > I should have written "If you call a tail ..." Lincoln is reported to > have cut through a sophistic argument put forward by one of his cabinet > secretaries with, "If you call a tail a leg, how many legs does a sheep > have?" When the secretary answered five, he responded, "Four. Calling a > tail a leg a leg doesn't make it one."Ok.
