Protect sound card when using PC-based oscilloscopes

[grrr_arrghh]

Hi.

There seems to be quite alot of PC-based oscilloscopes around, but my sound card is integral to my motherboard, and if I blew it up replacing it with the same model would cost about £150. You can understand why I am slightly nervous about it.

I need to make sure that my computer is protected from large currents, voltages etc. Do I need resistors? Transformers? Optoisolators? Resistors? Buffers? What?

As long as the signal going into the computer is pretty much the same as the signal being messured, and my computer is SAFE, I'm happy.

Thanks

Tim

 

[kentken]

From what I read about the subject, a card works good. The Pci slot, etc. has a protection circuit built in. (some might not)
Find a friend that has some old sound cards that he don't use.
Better yet, find another pc, then you don't need to wory is something happens.

Have fun

 

[grrr_arrghh]

Better yet, find another pc, then you don't need to wory is something happens.

If I had that much money, I wouldn't be here asking questions!!

P.S. I don't want to use an old PC, because I want to be able to use one PC for everything

 

[Optikon]

From what I read about the subject, a card works good. The Pci slot, etc. has a protection circuit built in. (some might not)
Find a friend that has some old sound cards that he don't use.
Better yet, find another pc, then you don't need to wory is something happens.

Have fun

This is incorrect. PCI slots do not have protection built in.

In general, do not trust anything in a PC to have robust protection available. To be sure, you had better provide your own.

 

[grrr_arrghh]

This is incorrect. PCI slots do not have protection built in.

In general, do not trust anything in a PC to have robust protection available. To be sure, you had better provide your own.

I though it was a bit odd. And I don't trust PCs to have anything, unless I know they have.

My question is, how to I provide my own protection?

Thanks

Tim

 

[ante]

Tim,

You can use zenerdiodes for protection. You should use an attenuator for this, look at this site: **broken link removed**

Ante :roll:

 

[grrr_arrghh]

err, thanks

does anyone speak swedish (?) or nowegian, or whatever it is? :lol:

err, and what is an attenuator? What do zener diodes do?

Tim

 

[diode]

I don't speak norvegian, but I can guess: "Klikk her for å se skjemaet", will bring you to the schematic, anyhow, this is a direct link to the schematics for that box: **broken link removed**

 

[grrr_arrghh]

oh, ok thanks

I assume 'Signal Inn' is connected to the signal I want to measure? And 'Signal Ut' is connected to my computer soundcard?

Can I ask what the point of the AC/DC switch is? And the rotary switch? And the potentiometer? How do I know where to set them to?

Also, the ground on the probe connection - do I NEED to connect this to the ground in my circuit?

Thanks again

Tim

 

[Nigel Goodwin]

oh, ok thanks

I assume 'Signal Inn' is connected to the signal I want to measure? And 'Signal Ut' is connected to my computer soundcard?

Yes!.

Can I ask what the point of the AC/DC switch is? And the rotary switch? And the potentiometer? How do I know where to set them to?

The switch is for selecting AC or DC input, it's a perfectly normal scope control, and frequently used.

The rotary switch is a coarse gain control (switched attenuator), and the pot is a variable gain - you set them, as with anything, to suit what you are trying to measure.

Also, the ground on the probe connection - do I NEED to connect this to the ground in my circuit?

You need to connect it 'somewhere', it's usually conected to the ground of the circuit you're testing, but not always - again, it depends what you are trying to do - but you MUST have both connections.

I don't wish to appear rude, but these questions are extremely basic, if you need to ask them you probably shouldn't be trying to use a scope. Bear in mind the protection afforded to the PC is fairly slight, not knowing what you are doing could easily blow your PC.

 

[grrr_arrghh]

I don't wish to appear rude, but these questions are extremely basic, if you need to ask them you probably shouldn't be trying to use a scope.

hmm, its a fair point. My knowledge of electronics is extremely basic, it was just that when I realised that I could have a reasonable scope, for the price of a few components, I saw the opportunity to learn something! Although to be fair, lots of pretty lines on a computer screen will mean very little to me...

Bear in mind the protection afforded to the PC is fairly slight, not knowing what you are doing could easily blow your PC.

That did worry me, and that was why I was asking lots of questions. To be honest, I'd rather not have a scope at all, than risk seriously damaging my PC...

The rotary switch is a coarse gain control (switched attenuator), and the pot is a variable gain - you set them, as with anything, to suit what you are trying to measure.

hmm, that was what I had assumed. The problem I have is that being very inexperienced, even if I knew what I was trying to measure, I wouldn't know where to set the controls!! You can see my problem.

I don't wish to appear rude

No, you wern't being rude, and I appreciate the honesty. Do you think I should just not bother with this, and do something more worthwhile in my quest for electronics greatness (!) ?

Thanks

Tim

 

[ante]

Tim,

Never give up, just try to find some info on how to use a scope and start from there. Often there is info on waveforms included. When you know the basics of the scope you will know if it is for you or not.

Ante :roll: