Comments for https://wellys.com/posts/lab_acsignals/
Comments for: https://wellys.com/posts/lab_acsignals/
- KKevin Rowney @krowney
Hi-
Great post and thank's for all this useful background education on Labrador. I'm trying to learn AC circuits from scratch, and this site is quite helpful.One total beginner's question for you: I see "earth ground" symbols in so many of the AC circuits, and I am aware of the pretty significant safety factors in higher voltage AC circuits. Earth-ground is absolutely vital for these. In lower voltage hobbyist circuits, I see the earth-ground inverted triangle symbol in those circuits all the time; but pictures of the circuits assembled on to a breadboard don't usually look like there is an earth-ground hookup. I also don't see one on the Labrador.
Do you have any guidance here on this? Obviously, I could just hook up any earth-ground terminal to the earth-ground outlet on my power supply; but I'm still left wondering what is best-practice with Labrador.
Any advice you can offer?
best wishes,
kevin
- KKevin Rowney @krowney
After a bit more reading, I now am beginning to understand that the ground symbol appears to represent the base ground voltage; so I as far as i can tell it looks like you measure v_in and v_out over time as voltage levels that are relative to the base ground. i'm also getting the sense that my concern related to earth-ground hookup for safety is just not an issue for these circuits.
Hoping i have this right. If you have any additional perspectives, would be grateful for your point-of-view.
- LLief Koepsel @lkoepsel
Hi Kevin,
Thank you for your questions.
First, yes, earth-ground connections are vitally important for higher (> 20V) AC (and DC) circuits for safety. And it is very important to be aware of your ground paths and ensure you are well are grounded in these higher voltage circuits.
That said, having a significant ground protection when using the Labrador on 5V or 3.3V is not necessary. The voltage and the current involved are quite small and aren't a concern. This is not to say you can't hurt yourself if you don't follow good lab practices, so please ensure you turn off or unplug circuits when creating them and be diligent when you are touching probes to points on a live circuit.
The other important aspect of grounding your circuit is to reduce noise and make accurate measurements. For this part, I recommend you share a common ground between the Labrador and the circuit under test.
This last part can be an issue if you attempt to power a circuit with USB as well as the Labrador from the same device. I have significant issues doing this and now I will power the circuit with a separate power supply if I need a negative voltage. In other words, I will use the Labrador to power a circuit if I need only one voltage ex:Labrador Lesson: AC Signal Analysis.
If I need an additional negative voltage, I would add it with another power supply, not with another USB powered power cable.
Lief