Question about Oscilloscopes

[QSilver]

Hey,

I am looking into getting an oscilloscope and I'm new to them so I wanted to know if I wanted to measure a 110V signal, can any oscilloscope do this? It's for a servo board on a Pioneer RT-707 open reel tape player and I don't want to get a scope that cant measure that.

Is it to do with adjusting the signal attenuation?

Thanks,
QSilver

 

[Jon_Logan]

Two things:

Thing 1: (Dr. Seuss ripoff)
If it is an AC signal, you need a scope fron end that can handle 2*1.41*the AC signal or 2*1.41*110(VAC) = 310V

Thing 2:

If the AC is directly connected to the mains (which I think it is), you need an isolation transformer to float the whole machine, so the scope lead can be grounded to measure the AC.

 

[dshoaf]

Servo systems are always tough to diagnose since they are closed loops - no matter what tools you choose to use for your diagnosis.

A scope can help but you have to be able to 'visualize' what the right waveform will look like to know if what you're looking at is ok.

Next problem you have to deal with is a dangerous one: measuring 110VAC (what your post referred to?) with a scope without isolation of the grounding is a recipe for personal disaster. I, personally, have had a ground to a scope probe melt in my hand when I wasn't paying attention to this - I was measuring 220vAC at the time.

Lastly, to your question of signal inputs, all scopes will spec upper limits of what voltage levels are acceptable. Most lab-level scopes will deal with the voltages we tend to see in solid state gear we see.

Cheers,

David

 

[QSilver]

Servo systems are always tough to diagnose since they are closed loops - no matter what tools you choose to use for your diagnosis.

A scope can help but you have to be able to 'visualize' what the right waveform will look like to know if what you're looking at is ok.

Next problem you have to deal with is a dangerous one: measuring 110VAC (what your post referred to?) with a scope without isolation of the grounding is a recipe for personal disaster. I, personally, have had a ground to a scope probe melt in my hand when I wasn't paying attention to this - I was measuring 220vAC at the time.

Lastly, to your question of signal inputs, all scopes will spec upper limits of what voltage levels are acceptable. Most lab-level scopes will deal with the voltages we tend to see in solid state gear we see.

Cheers,

David

I've got a service manual and diagrams of what the various signals should look like. This is not direct mains it is on a circuit board driving a capstan motor. I'm still a little confused about scopes. Are they in anyway similar to a multimeter in terms of settings eg 20VDC or 20VAC etc etc?

Am I right in thinking that if I was going to probe this circuit board and it was at 100V I would need to set the input attenuator to something like 0.5?

Thanks,
QSilver

 

[dshoaf]

Ok, I see. It appears you're asking some basic-use type of questions about scopes. Many scope owner's manuals assume you know how to operate scopes and just describe the actual features of that scope.

This is great and, to your point on measuring voltages, the short answer is that you can measure either AC or DC voltages using the grids on the screen. The types of probes you will use, however, will determine what settings you will choose.

Here's a good, quick discussion of the use of 10:1 probes, some of the more common probes you'll find.

On a more broad discussion, I'd suggest you start here first and work down to the probes themselves.

Generally, scopes assume much like their owner's manuals that you have a certain understanding of electronics so that you can interpret the results you are measuring. This can be tough and I understand starting out can be confusing.

Hope the links help get you started!

Cheers,

David