Understanding Oscilloscopes: Measuring Amps Directly

A quick tip to show how to measure current in your circuit directly on your oscilloscope, including values and labels. We use a popular, inexpensive, and very powerful RIGOL DS-1054Z scope.

[@alocin110]

FYI: Oscilloscope measures frequency, phase difference, and volts. What you are doing is not what many engineers and researches would like to do. The big question for you is about the phase difference. Can you use two channels on reading volts cross that resistor and other reading current; well then would it should the phase difference bet current and volts? Thanks for your reuply in advance.

[@EETechStuff]

Oh really? I've been an electrical engineer for over 45 years, and none of what you say is true. Oscilloscopes are used to measure FAR more than you say, including frequency components, rise time, peak values, i squared t, digital waveforms & decoding, and hundreds of other things. And you think we don't use them to measure amps directly? That's just not true. It's a great way to prevent calculation errors, by having the device do the volts to amps conversion for us. In fact we often use the scope's ability to program arbitrary equations to measure complicated values. Look at my video on "Calculating Energy on a Scope" for just one example of how to determine if a pulse of current will cause a fuse to blow. And your question about phase angle between resistive current and voltage makes no sense. There is no phase angle. Are you an engineer, or do you just make Minecraft videos?

[@bumpymotors]

@@EETechStuff Ooooo it burns!! lol PS: I like Minecraft videos...

[@bumpymotors]

Couldn't you just leave your probes at 10x, use a 100W 0.1R and (providing you oscilloscope is set to 10X in your probe list by default) just change your units to Amps? 1/.1=10X

[@EETechStuff]

Of course. Assuming you have a 0.1 ohm resistor available. What I showed in this video is a simple method, but typically what I do is use the scope's ability to program an arbitrary equation, so you can even use a resistor with a measured value of 0.683 ohms and leave the probe at 10x.

[@bumpymotors]

@@EETechStuff Thats awesome, I have a big aluminum shielded .1 ohm resistor to work with already. Thank you EETechStuff.

[@EETechStuff]

Just be careful. If you're going to use it to measure current, it's quite likely a 0.1 ohm resistor doesn't have a resistance close to 0.1 ohms. Check out my video on Power Resistors from a couple years ago. Especially cheap power resistors can have a resistance that varies greatly with load current and temperature, throwing your current measurements out the window.

[@bumpymotors]

@@EETechStuff Great advice, thanks again.