Bueno. Now, is your PC a desktop or laptop?

 

Thank you very much again, and sorry if I am making too much questions

Just had to comment, there is no such thing as too many questions (assuming you actually want to learn, which you seem to)

 

By the way, at the back of the oscilloscope it says "Fuses inside" (you can see it in one of the images i posted above). Does that mean i don't have to include any fuses in the wall plug?
Thank you again

 

Bueno. Now, is your PC a desktop or laptop?

It's a laptop, which makes me think that maybe its ground is not the plug's ground, but the batteries? Or maybe im completely wrong haha

 

By the way, at the back of the oscilloscope it says "Fuses inside" (you can see it in one of the images i posted above). Does that mean i don't have to include any fuses in the wall plug?
Thank you again

Wall plug doesn't have fuses your house does.

 

It's a laptop, which makes me think that maybe its ground is not the plug's ground, but the batteries? Or maybe im completely wrong haha

It was an important question.
Most laptops are not grounded hence we have to pay attention to how to properly ground external add on circuits and scopes.

 

Wall plug doesn't have fuses your house does.

Some Euro plugs have the fuses in the plugs.

 

MrChips, would you please elaborate on the grounding issue for laptops?

 

Sure. With pleasure.

If you run a laptop on its internal batteries then it is not grounded.
If you plug in the adapter/charger, you should make a note that most chargers are also not grounded.
In either of these cases this is not an issue of safety either for the user or the electronics.

The problem occurs when you attempt to use an oscilloscope in order to view a waveform on an external circuit attached to the laptop via the USB, as an example.

Scopes are grounded via the AC wall plug for electrical safety.
Scope probes come with a grounding clip that clips on to the probe.
To properly view a signal in a circuit you need to connect the grounding clip to what you have confirmed to be the COMMON reference point in the circuit.

In all of the situations I have encountered, the GND on the 4-pin USB signal is an acceptable COMMON reference.

 

From what you say I don't see the danger to the laptop.
For any two wire charger connected to a laptop the computer is floating, not grounded.
Connecting a mains ground to the USB ground thru an external device is still not a problem?
I say this because I believe that mains ground and scope chassis & signal ground are the same if the scope is not 'floating'.

 

I never said there is a danger.

All I indicated is that you have to connect the scope and the laptop to a COMMON reference point.

 

Thanks for the answer! I didnt get it completely clear though... The yellow green wire has no end... I understand it is not 100% necessary, but advisable for security issues... Is it in this case VERY advisable?
As well, how can i know, in a normal plug socket, which one is live and which one is neutral? I'm spanish and here the plugs are simetrical...
Finally, you say i will need a fuse. Does that mean that i have to add a fuse between the plug and the oscope?
Thank you!

In the 80s almost all TVs had live chassis, so some repairmen disconnected the earth lead inside the scope's mains plug - but this is *VERY* naughty and you shouldn't do it!

 

Hello,

What is your local mains voltage?
What kind of plug is normaly used in your country?

Bertus

 

Hello,

What is your local mains voltage?
What kind of plug is normaly used in your country?

Bertus

The local mains voltage is 220V, and the plug used here is the one with two cylindrical connectors, here a picture:

 

The local mains voltage is 220V, and the plug used here is the one with two cylindrical connectors, here a picture:

It may seem a bit obvious - but I'd have a quick look inside the scope to make sure the end of the mains lead isn't all that someone's mucked about with.

 

It may seem a bit obvious - but I'd have a quick look inside the scope to make sure the end of the mains lead isn't all that someone's mucked about with.

Seems like someone could have made it into a scope for field use. Pack a mini-inverter inside and run it on 12 volts DC!
Too late for this comment though, he already said it fires up on mains power.

 

Seems like someone could have made it into a scope for field use. Pack a mini-inverter inside and run it on 12 volts DC!
Too late for this comment though, he already said it fires up on mains power.

There should be a sound clip gallery of the sound when something unsuitable is plugged into the mains - my favourite is; "Ponk".

 

There should be a sound clip gallery of the sound when something unsuitable is plugged into the mains - my favourite is; "Ponk".

I have a big, heavy 32" Philips CRT Television in my basement that makes a similar noise when I turn it on. A big Gjoink - when powered up. It startles everyone in the room every time it happens. I thought it would crap out in the first week I had it but it has managed to startle people for nearly 15 years!

 

That would be the demagnetizer.

 

..AKA degaussing coil.
Max.