Oscilloscope newbie what is this noise? - Page 1
Forum section: electronics / beginners

author: Superkryptonite
author_rank: Contributor
timestamp: January 01, 2024, 04:50:50 am
content: Hi guys,I'm very new to oscilloscopes. I have a Pico 2204A.I am testing with a E3F-DS30C4 proximity sensor. I was wondering what this noise is in the waveform. I tried adjusting all my settings but still getting it. I've seen other people using the same sensor and they didn't have the same noise. Is this a problem with my settings or some noise that is generated from my power supply (5v from an Arduino) or something else?Was using 2s/div, with I believe 1Ms/s sampling rate which is what others have used as well.The sensor works fine, more just a curiosity on my part.Thanks!

author: ataradov
author_rank: Super Contributor
timestamp: January 01, 2024, 05:14:24 am
content: What does your test setup looks like? What probes are you using? Your amplitude appears to be very low, you can see individual levels.

author: Superkryptonite
author_rank: Contributor
timestamp: January 01, 2024, 05:38:03 am
content: Quote from: ataradov on January 01, 2024, 05:14:24 amHi thereFor my test setup I am using the stock PicoScope 2204A with it's original test probes (I'm not sure what type they are, sorry). Only using 1 probe, connected to the black sensor wire of the E3F-DS30C4. Brown wire from the E3F-DS30C4 connected to +5v output on my Arduino D1 (all I had lying around for 5v supply right now), and blue wire from the E3F-DS30C4 connected to the GND pin on the Arduino. The Arduino is powered through USB on my computer. I tried connecting the ground coming from the Pico's probe to the GND pin on the Arduino but it didn't change anything (when should I be doing that, anyway?)The sensor works on 5v DC and I was using 10v for the vertical scale, DC coupling mode

author: ataradov
author_rank: Super Contributor
timestamp: January 01, 2024, 05:44:26 am
content: Usually those types of sensors use open drain output. You need to have external pull-up resistor to +5V connected to the black wire. This is likely the reason for your low amplitude, you are just picking up some residual levels.What do you mean by "10V for the vertical scale"? What is the V/div setting?Also, does you probe have 1x/10x switch? What is it set to? Does it match the scope setting?

author: Superkryptonite
author_rank: Contributor
timestamp: January 01, 2024, 06:11:40 am
content: Quote from: ataradov on January 01, 2024, 05:44:26 amSorry I guess v/div you referred to is the correct term for the 10v I had mentioned beforeYes it does have the 1x/10x switch. I had it on the 1x mode. And yes in the scope settings it's set to no scale probe.

author: ataradov
author_rank: Super Contributor
timestamp: January 01, 2024, 06:18:28 am
content: This is the stupidest scope UI I've seen so far. On your waveform screenshots you don't include the scale, so it is hard to tell what is going on.Set the both the scope (I assume on the "Probes" tab) and the probe to 10x and then forget that 1x exists.And in any case, add 1-10 kOhm pull-up resistor.

author: tooki
author_rank: Super Contributor
timestamp: January 01, 2024, 05:55:39 pm
content: Quote from: Superkryptonite on January 01, 2024, 06:11:40 amNope, not the same thing. A div (“division”) means one “box” between axis tick marks. In your image, we see that each box is 2V, because the tick marks are at 0, 2, 4, 6, 8, and 10V. So your vertical scale is 2V/div. Like ataradov, I’ve never seen a scope display labeled as a vertical range. It’s not wrong per se, and arguably easier for a beginner to set up, but it’s totally nonstandard. Note that it’s normal to be able to adjust the vertical position, so even if you stay at 10 divisions at 2V/div, you might be showing 0 to 20V instead, or -3.5 to +16.5V. This is normally done by actually reconfiguring the analog front end of the scope. It seems some models of picoscope hardware are not capable of that, so while their software can let you change the scale and position, on those models it’s doing so purely in the digital domain, meaning a loss of resolution. (This is the “analog offset” range specification in the picoscope specs.)

author: pcprogrammer
author_rank: Super Contributor
timestamp: January 01, 2024, 08:00:31 pm
content: The power supply source mentioned for the test is 5V from the arduino connected to the USB port of a PC. This can be a very noise power source, and introduce the noise seen on the scope.Try just measuring the 5V, you use, with your scope and check if the same noise is seen there.

author: BeBuLamar
author_rank: Super Contributor
timestamp: January 01, 2024, 11:58:59 pm
content: I think the noise is from your power supply. Also the sensor has an NPN transistor output so without a pull up resistor you would have the have it switch the ground on and off (which works well for sensing application) and the scope may not read correctly with the ground switched off.

author: BeBuLamar
author_rank: Super Contributor
timestamp: January 02, 2024, 02:37:59 pm
content: Also operating the sensor with 5V is a bit low. The specs called for at least 6V. Most of the time the sensor is used with either 24V or 12V. 24V is more common.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: January 02, 2024, 03:13:06 pm
content: The first step is to zoom in on the signal to see what that noise actually look like.Second step is to use another probe to poke around and go looking from where the noise comes from, and the power supply itself is indeed likely the cause.

author: Jwillis
author_rank: Super Contributor
timestamp: January 03, 2024, 10:45:22 am
content: V/Div Volts per division is the amplitude of the signal (Vertical). What's the Time/Div (Horizontal). There should be a setting for that somewhere. It will be a scale in factions of seconds like nano seconds,micro seconds and milliseconds. It will allow us to figure out what frequency the noise is occurring and possibly identify where it's coming from.Keep in mind that oscilloscopes are very sensitive instruments and will pick up random RF noise from all around. Keeping the ground connection of your probe as short as possible can eliminate most but not all ambient RF noise.

author: BeBuLamar
author_rank: Super Contributor
timestamp: January 03, 2024, 10:58:49 am
content: With the OP software setting the range of +/-10V means 2V/Div.

author: pcprogrammer
author_rank: Super Contributor
timestamp: January 03, 2024, 11:08:59 am
content: Quote from: Jwillis on January 03, 2024, 10:45:22 amIt also varies from scope to scope. My Hantek DSO2D10 showed 150mV peaks of noise when the probe was connected to a, for the rest unconnected, 8.4V battery pack. The same setup with my Rigol MSO5074 showed only peaks of 10mV. (Was to check on output noise of a buck converter connected to the battery)The internal power supply of the scope and its internal design with shielding, etc, can be of influence on this too.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 03, 2024, 11:50:27 am
content: this was from picoscope have you setup your probes types correctly ... have you experience from using it ?