I am new to electronics and now I wanted to try to use an oscilloscope to measure a PWM output signal.
I made a simple circuit with a Raspberry Pi Pico microcontroller and connected an LED on a breadboard with a resistor to a GPIO. I wrote some code to use PWM on this GPIO and got the result that I expected, the LED is lit up, but not fully. The frequency I tried to use is 40kHz.
Then I connected my oscilloscope for the first time. It is a GW Instek GDS-1054B. I only use a single channel probe for this task. The only adjustments I made on the oscilloscope is to adjust the vertical scale and the horizontal scale while running.
I expected to see a clear square wave and hopyfully some interesting data about time and frequency, but instead, even when in a stopped mode, I get multiple quite blurry square wave lines. This is the best result I could get when using the scale adjustments. What am I missing? Is this the best it gets? There are almost no useful numbers in the picture. I see a frequency data point, but it seem to change when I change the scale. When I scale out, it seem to be about ~49kHz and when I scale in, it gives me a number around ~2.x kHz - not what I expected to see.