Its my first time using oscilloscope, I was trying to read output from AS1117 on an Arduino board, and this is what I get.
I was expecting square wave, but its nothing like it. Am I doing something wrong or is it supposed to look like this?
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1\$\begingroup\$ The output of an 1117 should be a pretty constant voltage. The noise you're seeing is probably from the microcontroller doing something. Why do you think it should be a square wave? \$\endgroup\$– HearthSep 29 at 18:04
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\$\begingroup\$ Try connecting the probe end to the clip and touch the output and, see what you see. \$\endgroup\$– Andy akaSep 29 at 18:33
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\$\begingroup\$ Did you hit autoset? This button has pretty poor artificial intelligence. What autoset finds interesting is sometimes not what you want to know. Perhaps you wanted to know that's this regulator is outputting +5V? Notice that the zero volt reference is offscreen-bottom. What you're looking at is close-up details on that +5V DC \$\endgroup\$– glen_geekSep 29 at 18:35
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\$\begingroup\$ @Hearth Since its DC current, shouldnt it be square wave? \$\endgroup\$– AlkyoneSep 29 at 19:20
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\$\begingroup\$ @Andyaka You mean connecting probe to the ground clip? \$\endgroup\$– AlkyoneSep 29 at 19:21
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3 Answers
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First of all, you are measuring output of a DC regulator, so you should expecy a straight horizontal line at the set value.
Secondly, you seem to be powering your Arduino with a switch mode power supply. It will have some switching ripple zoomed in on that scale.
I'd expect that's pretty much what you should see.
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\$\begingroup\$ Oh, am i completly misunderstanding what output should look like? It should be constant 5V instead of square wave ranging from 0V to 5V? \$\endgroup\$– AlkyoneSep 29 at 19:25
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\$\begingroup\$ Arduinos and most other devices work on DC as power supplies. They don't work on square waves as power supply. It might be interesting to hear why you expected a square wave out of a DC regulator though. \$\endgroup\$– JustmeSep 30 at 7:35
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\$\begingroup\$ To be honest i have no idea where this square wave concept came into my mind from. I always thought that DC power supply provides square wave instead of constant voltage, Its kind of embarrassing to be honest. \$\endgroup\$– AlkyoneSep 30 at 20:03
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At frequencies this high, it's most likely common-mode noise, transmitted between cables and connections that are not well balanced at radio frequencies.
Consider that the probe's ground lead has an equivalent inductance in the 100nH ballpark. What reactance does that have at this frequency? And what could that say about interference picked up by the scope probe? Suppose that the ground you are probing against has 1V peak at 80MHz on it: what would you then measure?
answered Sep 29 at 18:19
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\$\begingroup\$ Too be honest, i'm way too incompetent to answer that question. I'm just begginer trying to do some things for fun. \$\endgroup\$– AlkyoneSep 29 at 19:33
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Looks like noise from an unconnected probe. Make sure you have ground on the probe connected to a ground on your target and the probe connected to the desired pin. Once you have that make sure you have your trigger and timebase set according to the signal you are trying to capture. If you are new to oscilloscopes I would suggest getting used to the connections and trigger control by connecting to the cal connections on the front of the scope. They provide a reference square wave.
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\$\begingroup\$ Its connected. I was already using front generator to calibrate compensation so i think i have basic understanding of setting trigger and time base. \$\endgroup\$– AlkyoneSep 29 at 19:29