Circuit(s) to teach basic oscilloscope functions - Page 1
Forum section: electronics / beginners

author: pixelkind
author_rank: Newbie
timestamp: February 17, 2020, 09:03:26 pm
content: Hello everyone,I run the electronics lab in a big maker space and currently setting up workshops to teach our members the basics on how to use the equipment.I was wondering if there are any ready-made circuits out there to help me teach the usage of oscilloscopes or if I have to design something myself. I know some companies got boards to show off some functions. What would you put into a basic class/workshop to teach the usage of an oscilloscope? Without needing to explain too much about the electronics itself. It should focus on using the scope.Thanks a lot!

author: Wimberleytech
author_rank: Super Contributor
timestamp: February 17, 2020, 09:49:41 pm
content: An oscillator that provided a square wave and a sine wave output.It would need to have a variable frequency.Have the option to drive an RC to measure rise time of an exponential.This video might give you some ideas. There are others on youtube as well.

author: RoGeorge
author_rank: Super Contributor
timestamp: February 17, 2020, 09:52:27 pm
content: Any oscilloscope have a square signal generator for probe calibration. That signal should be enough for teaching the basics.

author: Gyro
author_rank: Super Contributor
timestamp: February 17, 2020, 10:21:23 pm
content: An XR2206 based function generator board is probably as good as anything, giving you Sine, square, and triangle with variable amplitude and frequency. For example:https://www.ebay.co.uk/itm/XR2206-Sine-Triangle-Square-Output-1HZ-1MHZ-Function-Signal-Generator-DIY-Kits/163307056802Although you would be best advised to find a local seller at the moment.Most other stuff tends to be DDS these days, but they don't really give you many options for practising probing around the PCB.

author: daqq
author_rank: Super Contributor
timestamp: February 17, 2020, 10:27:08 pm
content: RC oscillators are nice. Maybe a microphone and a whistle?A nice visual demonstration might be passing light through the fins of a fan and measuring the rotational speed by sensing the light on the other side via a phototransistor. This way you can demonstrate how to manually read the frequency/period of the pulses and calculate the RPM from that information. Also, demonstrate slowing it down with your hand?

author: Kasper
author_rank: Frequent Contributor
timestamp: February 17, 2020, 10:59:13 pm
content: Good way to practice with the trigger and time/div settings is to look at button bounce.Voltage supply, resistor and button all in series, maybe an led too. Oscilloscope across button. Be careful where scope gnd gets connected!If scope trigger and time/div are setup well the user should see bouncing for about 10ms when button pressed or released. This answers a common beginner question, "why does arduino get multiple triggers from 1 button press".To go a step further you can add a debounce circuit to fix the bouncing problem and show what capacitor charge and discharge look like.

author: Kasper
author_rank: Frequent Contributor
timestamp: February 17, 2020, 11:07:44 pm
content: First lab I had in electronics school was frequency generator, speaker and oscilloscope. I found it really helpful to relate the electronic signal to a speaker which could be seen and heard and we all had fun playing with the frequency and amplitude.

author: Shock
author_rank: Super Contributor
timestamp: February 18, 2020, 12:04:57 am
content: Tektronix used to have a microcontroller lab based training course for teaching oscilloscope signals. If I recall correctly it was for the arduino and there was a pi version. They updated their website a few years back and I can't find it anymore. I'm not sure if you need an make an account to get access to this anymore or what but it seemed a very comprehensive course, let us know if it's still online. You can access some of the pdfs via the way back machine.https://web.archive.org/web/20150403214143/http://www.tek.com/courseware/search?field_courseware_categories_value=1900https://web.archive.org/web/20150407230300/http://www.tek.com/sites/tek.com/files/courseware/ST_Arduino_Labs_Combined.pdf

author: IDEngineer
author_rank: Super Contributor
timestamp: February 18, 2020, 12:50:05 am
content: Quote from: RoGeorge on February 17, 2020, 09:52:27 pmI'll add a vote for a function generator. A square wave by itself does not really allow visualization of varying trigger levels. You need something slower than a square wave's edges for that, like a sine or triangle/ramp. Then you can literally watch the waveform "move" as the trigger level is varied. This makes the behavior of the trigger instantly intuitive. IMHO the trigger is one of the most powerful aspects of a scope, and it's important for newbies to really grok what is happening.Another handy signal source is any sort of analog video camera, as is found in (far too many?) devices these days. Almost all scopes have H and V triggering which handles holdoff, allowing a single line or frame to be easily displayed. Zooming in and out (with the timebase) while triggered makes the horizontal sweep timing very clear, and the ability to wave your hand around in front of the camera and "see" the effect on the analog video data is another very intuitive demonstration. People can relate to video cameras since they're surrounded by them these days.I've done the above in under 10 minutes with utter newbies - never touched a scope before - and they were then able to describe and demonstrate how a scope works to another newbie. Some of the terminology wasn't quite right, and they fumbled with the controls, but they *understood* what was happening and could demonstrate it given enough time. That's a win in my book for <10 minutes invested!

author: rstofer
author_rank: Super Contributor
timestamp: February 18, 2020, 02:18:46 am
content: There's an oscilloscope training class linked at the top of this forum.

author: vk6zgo
author_rank: Super Contributor
timestamp: February 18, 2020, 02:33:24 am
content: Quote from: IDEngineer on February 18, 2020, 12:50:05 amGet them to look atfield rateanalog TV signals, by all means, but better use a pretty decent DSO or an analog 'scope.A very cheap "pretend" 'scope won't be able to display such signals properly, neither will a very old DSO.On second thought, a terrible "El Cheapo" DSO compared with a good one, or an analog 'scope might be a good "teaching moment".You can ask themwhythe field rate display doesn't work!

author: David Hess
author_rank: Super Contributor
timestamp: February 18, 2020, 06:16:17 am
content: I always liked switching regulators for testing the basic functionality of oscilloscopes. Triggering on or displaying the reverse recovery waveform of the rectifier is a good use for delayed sweep and trigger after delay.

author: pixelkind
author_rank: Newbie
timestamp: February 18, 2020, 08:36:29 pm
content: Thanks a lot for all the input!I like the button bounce a lot. Also the RC oscillator.We have function generators but I prefer some "real" circuits to show as well.

author: tunk
author_rank: Super Contributor
timestamp: February 18, 2020, 08:59:22 pm
content: Could this be an alternative:https://www.velleman.eu/products/view/?id=387510

author: pixelkind
author_rank: Newbie
timestamp: February 18, 2020, 09:43:06 pm
content: Quote from: tunk on February 18, 2020, 08:59:22 pmVery interesting. Thanks a lot

author: Wimberleytech
author_rank: Super Contributor
timestamp: February 19, 2020, 12:20:00 am
content: Quote from: tunk on February 18, 2020, 08:59:22 pmThat's cute. One thing I did not think about in my original response is that often times you are having to switch between AC coupling and DC coupling in order to get the magnitude of the average signal and the details of the signal sitting at the average. This board may force that issue.