How to Measure the Time Constant with an Oscilloscope

[@KeysightLabs]

Edit! tau = L/R not R/L. Great catch by @Rushiraj Jawale

[@catalin3407]

Yeah, you can correct the mistaken "L=di/dt" also at 6:00.

[@whocared9120]

4 years later and this is still the best explanation I've ever received thank you!

[@Tutoelectro1]

Great video, very clear! Thanks for sharing!

[@benjaminbrink5098]

This is timely. Thank you! I'm working on a project where it's important to separate first principle knowledge from knowledge based on standards. My RF knowledge is self learned, so will be using this packed video to review my work. Am looking forward to using an oscilloscope or network analyzer to diagnose where designs are breaking. ;-)

[@muhammadrafiqulislamkhan6994]

Thank you. Very easy explanation about Time constent.

[@Zeigren]

You guys are doing a great job with these videos, keep up the good work!

[@KeysightLabs]

Thanks!

[@mcwilleford]

Thanks for all your help! Use Analog and Digital in many projects, but never used a real oscilloscope. After watching many of your videos, it's clear I need/want the new 1000 X setup...very nice!

[@Trent-tr2nx]

Daniel is back!

[@christycampbell1874]

Very clear and friendly!

[@pankajroy5124]

*Great video. I came here on suggestion of GREATSCOTT. Since you are making very informative video I subscribed to your video. Great work. Keep it up.*

[@tektronix-videosenespanol-4033]

A really useful video. Thanks!

[@binaryglitch64]

I like how even though your talking directly to the camera/audience you still did an aside... like your letting us in on a little secrete lol.

[@KeysightLabs]

We like to mix it up :)

[@binaryglitch64]

@@geraldmartsy2165 I'm not the guy from mythbusters, if that's what your asking.

[@vencibushy]

Few months ago we went REALY old school at the uni. We tested pneumatic RC circuits.

[@tejasnakhate]

A really useful video. Thanks a lot👍

[@RobeenaShepherd]

The Bog is Back!!!! Bogdanites unite!

[@imanabu5862]

This is priceless ❤️❤️❤️ in lab course I have to do an experiment on electricity which is a subject/ course I haven't learned yet, with this simplified and deep explanation you just saved my Grades, and made both love the subject and get excited to the electricity course.

[@martinsimlastik5457]

Great explanation!

[@magnehaneberg8605]

I really like this video and I'd love to see more videos of this type (general education). It does however come in stark contrast to several other videos on this channel that comes across as shameless advertising for your own products. This type of video is how you can grow your channel to become big on YT.

[@KeysightLabs]

Thanks! We've definitely made a big effort to shift away from that older style of video.

[@aasmamir8271]

How do we choose reference points? Would you explain?

[@KeysightLabs]

You can sorta pick whichever point you want and do the math from there, that's the beauty of the time constant!

[@rtechlabs]

Great explanation! Practically calculating the time constant. I would like to know how to calculate different parameters like rise time, delay time, etc of a second order system as the characteristics of a second order circuit like damping, bandwidth depends on these parameters. BTW, there's a mistake in the video. Daniel in the video says tau = R/L but tau = L/R for a R-L circuit.

[@KeysightLabs]

Darn! Good catch on the mistake :( The 2nd order systems definitely get more complicated but would make for a good video!

[@snnwstt]

About the measurement on the scope, there is surely a "tracking mode" no? That would be way much simpler and precise to use that mode, since then, the "y" cursor (vertical, the voltage) always stick on the trace of the curve point which is at the given "x" cursor position (horizontal, the time)... so you don't have to manually match the vertical cursor, visually, as you move the x cursor, since then the y cursor automatically follows to be a point on the curve. Question: for supercap, which have a huge C value, how can we measure that time constant, since it takes forever to charge them, even with a relatively low external resistance? In that, do they (supercaps) have a constant C value (constant versus V) ? Or do their internal resistance interfere with the computation? From my experimentations, there is just too many possible variables, so I don't dare to risk any conclusion, but maybe you "know", in a way or in another, about these caps?

[@KeysightLabs]

Good question! Yes, there is a tracking mode, but it only works for the x-cursor (tracking a signal with the y-cursor could get quite complicated). But for this video I wanted to lead with the Y-cursor to keep the lesson a little cleaner. For a super capacitor, I'd probably recommend just calculating a value or handling it at a low voltage. You could partially charge it with a known current and measure the discharge. The concepts should hold true no matter what, though. For a time constant, you do have to have both an R load and a Z component (C or L).

[@markgreco1962]

Thanks for the sweet demo of the touch screen, now go rest up for scope month

[@KeysightLabs]

On it!

[@Niggels1404]

*Yes I want the scope!* Oh, wrong channel..

[@KeysightLabs]

Well, check out www.wavekeysight.com - we're doing a huge giveaway!

[@LegalSkateboarding]

Looks like I'll be brushing up differential equations skills :D

[@seanduggan144]

THANK YOU!!!!!!!!!!!!!!!

[@benjaminbadrakh1644]

I feel like im... well outdated when watching these videos because I still use my Tektronix 454 and 2235s. Along with some other HP and Hitachi scopes. Should I get a digitizing oscilloscope? My current scopes work fine for general analysis.

[@KeysightLabs]

If what you have does what you need, then great! I personally thing digital scopes have a lot to offer over analog scopes, but like analog scopes they are not perfect. If you have a project or application you need something more for, think about upgrading, but let your gear grow with you as you move to more complex projects and measurement challenges.

[@christoffere425]

How do you get the theoretical value of 104ms?

[@sanjursan]

Eric Dahl: He explain this at 5:00. Tau = R x C. Tau = 1k ohm x 100 microfarad = 100 millisecond.

[@Joseph-td2bf]

Cool!

[@stonecold7945]

2:33 What is that in the bottom right?

[@KeysightLabs]

That may or may not be a cutout of me from last Scope Month

[@sanjursan]

You say "rigorously measure," but then you eyeball cursors. Why isnt there a way to simply measure the time in seconds (an electronic stopwatch) for the process of filling the cap from zero to 63.2%? My very accurate frequency counter (Hp 5316A) has the capability of measuring time, but the method by which this timer is started and stopped by the activity of the circuit is not clear. In this case, of course, the input signal is a flat DC voltage. I have done this with a Tau of up to two minutes and used my cell phone app stopwatch. Results were repeatable to tenths of a second and far more accurate than cursors on a scope since all variables could be controlled to several decimal places. The large values of Tau are required since I was forced to manually operate the stopwatch, and (delta t)/t could be made small. Any thoughts?

[@praveenkumarr6751]

have need an formula or equation of the time constant of an rc circuit sir

[@saiham4500]

great vdo

[@KeysightLabs]

Thanks!

[@saiham4500]

how can i get a scope?

[@TrystansWorkbench]

SI Abid To get a scope you need to work hard, and save up your money. Then you can buy one just like this from Keysight Labs.

[@aasmamir8271]

Why 2 v as starting point not 0?

[@KeysightLabs]

It was easier to measure and made sure we were starting from a place that was known to be consistent, no unexpected LCR effects.

[@Muck-qy2oo]

I measure capacitance like that.

[@zaheera6899]

Currently I do all digital work i want to go analog and do all this. But no oscilloscope :( someday i will XD.

[@hershjoshi3549]

you can buy tools that connect to your laptop with built a built-in oscilloscope, logic analyzer, function generator, bode analyzer, etc. for $100-$300. They can't go that high frequency and the precision isn't the best, but they're still decent. I've personally used the NI myDAQ and the Analog Discovery 2.

[@zigmaex]

Annoying background music. Difficult to concentrate on what the host is saying.

[@shadowbane7401]

2π

[@nhisme9805]

Why are you using a $20K 1.5GHz scope to demonstrate such basic principles? It seems unlikely that people who are just learning about circuit fundamentals would be in possession of such equipment. For this purpose, a demo with your 1000x series may be more appropriate.

[@KeysightLabs]

The bigger screen works better on video, so I tend to use them for videos where the display data is crucial.