If you use a x10 or greater "real oscilloscope probe", the effective input Z become 10 Meg ohms.
The scope's 9 M is in series with the 1 Meg in the scope.
This
https://www.radio-electronics.com/info/t_and_m/oscilloscope/oscilloscope-probes.php is a better explanation.
Very short version:
The scope is typically 9 M in parallel with 22 pf. A 10 x probe is typically 1 M with a variable capacitor. The coax of the probe adds capacitance and you WANT the scope to see something purely resistive.
The artifacts show up at high frequencies and the edge of a square wave is composed of many frequencies (sorry, short answer says I won't discuss further). So, you get artifacts like shown in the photos. These ARTIFACTS are adjusted out by using the "calibrate" signal of the scope which is typically a kHz and a small amplitude.
So you adjust the variable capacitor on the probe, until you gate a square wave. On the x1 scale , if the probe has one, the adjustment is covered on most probes.
You could easily breadboard a X1 buffer and set the input Z to say 10 M with a resistor. Definitely not the best idea.
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You still have to remember these few rules
1) The voltage across a capacitor can't change instantaneously
2) The current through an inductor can't change instantaneously.
3) Twisting attenuates EMI (Electromagnetic interference)
4) Shielding attenuates RFI (Radio frequency Interference)
5) Earth Shields should be attached at one end (preferably the source of the signal).
6) Long distance transmission should be done differentially (think ethernet) or current (4-20 mA)
7) Avoid ground loops by design.
8) Simple rule: Types references can be kept together BUT only tied together at "one point". It's hard to achieve.
9) Follow the manufacturers recommendation for "bypassing". They are capacitors
VERY CLOSE to an IC's power pins and elsewhere as required. They are "REQUIRED".
10 Bypassing can be a parallel combination of different types of capacitors. (reasons I won't go into) except the capacitor construction gives the capacitors different characteristics.
11) Stuff that's seemingly unimportant can matter. e.g. The foil side of a non-polarized mylar capacitor can matter what side it's connected too in a circuit. Yep, a non-polarized cap being effectively polarized. e.g. less hum when connected when the foil goes to the low impedance side.
12) Don;t try to make pico-amps of current flow into a load of nearly 0 ohms. I did once,
13) Read the datasheet.
14) An unpowered circuit has Vss and Vdd = 0. So Vdd +0.3 means 0.3V
15) the elecron flow and "conventional current flow" are in opposite directions. Usually it does not matter.
16) I'l tell you that I have measured the resistance of a sheet of paper. 99.99999% of the time most people cant.
17) Numbers used to analyze can fool you. A 14 MW power plant is minus 14 MW. Power being positive is power dissipated. Generated power is negative.
18) Sometimes wierd stuff matters: 3 1K resistors in series is not 3K. SMT resistor mounted sideways have a different component value.A fingerprint matters. Conduction of electricity may be better in hollow silver plated tubes.
I challenged answers in college and won. One time I was told, your not supposed to know that yet. A solder (type of solder) copper joint may have more offset than another. A clean joint has less offset than one made form an oxidized copper. As I said, sometimes wierd stuff matters.
So, there's a few things that may help.