Current measuremt with SDS1104X-E - Page 1
Forum section: electronics / testgear

author: MathiasSven
author_rank: Newbie
timestamp: July 12, 2023, 12:55:00 pm
content: Hello!I was unsure whether this question would be more fit for "Beginners" or "Test Equipment", but because I am specifically talking about the SDS1104X-E I figured it should go here.This is my first oscilloscope, I have already read the manual, but I only saw one mention of current when it comes to measurements and that was in the "Unit" section. I can only change the channel label from V to A, nothing else like scaling is mentioned. My question is just, am I missing something? The value that would be displayed would only be immediately correct with a sensing resistor of 1\$\Omega\$, and having the correct value on screen aside, I would have to pick very specific values like 1, 10, 50, 100, 500, etc. In order to be able to immediately make sense of the value on screen.My thought is that since the oscilloscope has a math function where I can divide one channel by another, or a reference waveform, surely I should be able to just divide a whole channel by a fixed value, that seems to be an easier and less complex (computationally) task, but I also could not find anything in the scope that would allow me to do such a thing. I guess technically, I could run a DC waveform in one of the channels from my power supply, setting it to some significant figure of the value of my sensing resistor, so that afterwords I can divide the by it, and then further in my head the magnitude, but this is just a hack and I wouldn't really consider it practical?Are there any features that would help with quick current measurement that might be paywalled (that I could maybe unlock)?

author: delvo
author_rank: Contributor
timestamp: July 12, 2023, 02:02:49 pm
content: Im not home so i cant test it. but i think you should be able to set the multiplier where you set up 10x probes. There are a bunch of predefined values but if you scroll all the way down you can set custom ones.

author: Performa01
author_rank: Super Contributor
timestamp: July 12, 2023, 03:22:42 pm
content: For current measurements, you need a shunt resistor. Since the scope channels are grounded, you can measure a either floating circuit or you have to use a low-side shunt for current measurement.As member @delvo has already mentioned, you need the correct probe factor for this. Your shunt is the probe and if it's value is 1 ohm, then we can assume a probe factor of x1. If you want to use a 100 milliohm shunt, then the voltage will be ten times lower, thus requiring a probe factor of x10.If you intend to use some different value, like e.g. 25 milliohm, then you need a probe factor of 40, which is not a standard value, but can easily be defined and stored as custom probe factor.

author: MathiasSven
author_rank: Newbie
timestamp: July 12, 2023, 03:30:18 pm
content: Of course!I was fixed in looking for ways to post process the voltage reading from my probe from dividing to changing the scale that I completely forgot the basics that I could use the probe attenuation multiplier as such, and indeed after checking, he SDS1104X-E provides 4 custom settings that I can save and set to whatever value via the input window on top of all the predefined values.Thank you

author: bdunham7
author_rank: Super Contributor
timestamp: July 12, 2023, 03:43:08 pm
content: Quote from: Performa01 on July 12, 2023, 03:22:42 pmDon't forget the current clamps! For a 1mV/A current clamp, for example, you'd set the probe factor for 1000X and the units to 'A'. The same current clamp with a x10 line splitter would need a probe factor of 100X.