field test unit no 001 "model T"

[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

[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??

[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??

[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_online/topics/labintro/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 ?

[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.

[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_online/topics/labintro/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.

[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

[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

[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??

[dougAEGPF]

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

priceless!

dougAEGPF

[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.

[moodz]

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

[moodz]

Moodz, radio transmissions are sinusoidal??

PI is not sinusoidal.

ROFL ... "every" time varying waveform can be broken down to a series of sinusoids.

PI is a wideband time varying signal ( but can be described/analysed as a bunch of sinusoids)

Filters (except maybe some types of active filters ) dont care if the input signal is wideband or narrowband they just filter according their transfer characteristic.

A high pass filter will knock out lower frequencies in the stopband and let through higher frequencies in the passband.

[UrbanFox]

priceless

Pray tell, Davor, does capacitive coupling treat a sine wave differently to a non sine wave?? You tell me (smartarse )!!

Experience with a scope's AC coupling function will demonstrate that a slope will appear in the otherwise horizontal parts of a square wave. True or False???

[Davor]

priceless