field test unit no 001 "model T"

[UrbanFox]

...if a slope appears it means your CRO is cheap LOL

Sorry Moodz, your ignorance is showing.

Consider that DC can be removed with a high pass filter or capacitor, however, a square wave is made up of DC.

[dougAEGPF]

however, a square wave is made up of DC!!!!!

priceless!

dougAEGPF

[UrbanFox]

priceless!

dougAEGPF

Pray tell, Wally, if I take the segment of a square wave that comprises a peak component of that wave....excluding any varying voltage component at each end of that wave segment.....what do I actually have??

[moodz]

Sorry Moodz, your ignorance is showing.

Consider that DC can be removed with a high pass filter or capacitor, however, a square wave is made up of DC.

Dig up ... Dig up ...before its too late ....LOL

[dougAEGPF]

Pray tell, Wally, if I take the segment of a square wave that comprises a peak component of that wave....excluding any varying voltage component at each end of that wave segment.....what do I actually have??

You are a silly wanker, aren't you.

Why ask what you cannot answer yourself! But to help you here is my response.No doubt that any errors or omissions will be quickly jumped on!!

A square wave can be put together from, or decomposed into, sine waves of various amplitude and phase relationships. This is the basis of Fourier analysis. A square wave consists of a fundamental sine wave (of the same frequency as the square wave) and odd harmonics of the fundamental. The amplitude of the harmonics is equal to 1/N where N is the harmonic (1, 3, 5, 7…). Each harmonic has the same phase relationship to the fundamental.


It is I believe well known that the high frequency harmonic content, and not a DC component is responsible for the characteristic shape of a square wave. In fact, DC by its very definition cannot cause any frequency dependent waveform shape. The DC component of a signal is simply the average value of that signal.

Signals that are symmetrical about the time axis will have a DC value of zero. Signals that are asymmetrical about the time axis may or may not have a DC value of zero. If the area between the positive half of the waveform and the time axis is equal to the area between the negative half of the waveform and the time axis there will be no DC component present. If these areas are not equal there will be DC in the signal. ie, the average value of the signal has to be non-zero if there is DC present in the signal.
hope this helps you.
dougAEGPF

[UrbanFox]

Dig up ... Dig up ...before its too late ....LOL

Hey Moodz, could you explain what is being presented at this link...seeing that you dispute the quality/price of a scope if it displays what I have previously suggested when switched to AC coupling.

http://www.ee.usyd.edu.au/tutorials_...ro/acdist.html

Would I be right to say that with any waveform that is comprised of multiple frequencies, you don't see a need to consider that capacitive coupling will result in differing distortion over that range of frequencies??

I have the impression that you are conditioning readers to accept filtering as a significant design component to be used to achieve ground balance.

[moodz]

Sorry Moodz, your ignorance is showing.

Consider that DC can be removed with a high pass filter or capacitor, however, a square wave is made up of DC.

...and further to Dougs informative reply above if you are looking at a 1 KHz PPS pulse train then the minimum frequency component is 1 KHZ which is well above the 10 Hz cutoff input for AC inputs on your average CRO ... you are right a cap does block the DC but if you are seeing a "slope" on your CRO with AC coupling at 1 Khz then it is time for a new CRO.

[moodz]

Hey Moodz, could you explain what is being presented at this link...seeing that you dispute the quality/price of a scope if it displays what I have previously suggested when switched to AC coupling.

http://www.ee.usyd.edu.au/tutorials_...ro/acdist.html

Would I be right to say that with any waveform that is comprised of multiple frequencies, you don't see a need to consider that capacitive coupling will result in differing distortion over that range of frequencies??

I have the impression that you are conditioning readers to accept filtering as a significant design component to be used to achieve ground balance.

... the problem I was addressing was earth magnetic field NOT ground balance ( I solved that one already ) ... re-read the prior posts.

Is that link you posted the same model CRO you have .... figures ..... see PIC below ... see anything familiar ?

[UrbanFox]

...and further to Dougs informative reply above if you are looking at a 1 KHz PPS pulse train then the minimum frequency component is 1 KHZ which is well above the 10 Hz cutoff input for AC inputs on your average CRO ... you are right a cap does block the DC but if you are seeing a "slope" on your CRO with AC coupling at 1 Khz then it is time for a new CRO.

However, Moodz, what the issue is here is the use of AC coupling and how any distortion of the various components of the received signal will impact the analysis and processing of those signal components. We can go off on tangents and introduce strawmen arguments rather than look at the issue.

If we are talking a non-sinusoidal capacitive coupled waveform of short duty cycle, what do you see happening to the upper and lower amplitude values relative to DC coupling? Could this impact upon achieving a reference voltage needed for signal analysis??

[UrbanFox]

.. re-read the prior posts.

Sorry Moodz, i am falling behind re latest posts.

OK, Your graphic is showing probe compensation. I am talking about the effect a capacitor has in a square wave. Do you understand the difference??

[moodz]

The front end of a CRO is no different ... It's a ac coupled amplifier. .. My CRO works fine well below 10 hz on ac coupling. ... Oh now I see you are really talking about input impedance. ... Now that will cause waveform distortion if it changes with frequency. LOL

[Carl-NC]

Fox, I edited your prior post to remove the name calling. Keep it up and you'll be banished to Doug's forum.

I think you've overstepped your understanding of signals regarding DC content. You won't win on this one when you're that wrong. Read up on Fourier Series.

[Aziz]

A comb filter is what I was thinking of. Aziz, I think you will see this if you did a more detailed selection of frequencies.

Ok, I have found a transfer characteristics, which is exactly describing what you thought of and it's the more correct version of course, if we look more detailed at higher frequencies.
(I have cheated a bit outside the worst case scenario )

Look at this transfer characteristics (red):
http://www.musicanddesign.com/images/DW_eq4a.GIF
(not to scale with our table)

And you can see, when I begin to simplify (the cheat):
SubtractionMethodAttenuation.zip

But the high frequency region isn't much relevant for the EFE effect and low frequency cancellation. The low frequency transfer characteristics is much more interesting to show.


Someone could look at the subtraction of integrals now.

Cheers,
Aziz

[Aziz]

Fine. UFox is learning now. (I appreciate this. )

[UrbanFox]

Fox, I edited your prior post to remove the name calling. Keep it up and you'll be banished to Doug's forum.

Fair enough, Carl.

I think you've overstepped your understanding of signals regarding DC content.

Carl, i am just wanting to present that a non-sinusoidal waveform doesn't necessarily exit of a capacitor looking the same as it did when it went in. Multiple frequency signals, such as broadband signals, behave differently because capacitive reactance is frequency dependant. Also of some possible relevance, an AC coupled square wave will rise and fall when the duty cycle is varied.