USB digital scope

Judging by the clicks, many still do. Spectrum analyzers, too. A relay is hard to beat in some applications.

John

Relays are the best way to this job. They have great isolation when open, and are pretty good shorts across a wide frequency band, and survive transients quite nicely. There's nothing wrong with relays. Ever use a scope that's worth more than a house in California? It goes click-click-click too. Know what they're doing, the dudes who design those scopes. What I'm getting at is that it's a good sign.

Oh and let us know how the thing works, looks like a reasonable deal for tooling around lower frequency stuff.

There are ways of doing this with solid-state, but relays allow higher performance with greater design ease. All good digital scopes will still go "click-click-click" when you use them. The quality of the relays used will vary a lot between your el-cheapo eBay scope and a top of the line $100,000 Agilent or Tek though!

Dave.

Open it up and post a picture of the pcb. :)

D from BC British Columbia Canada.

I'd say, you can but a diamond from south america for thousands (or hundreds-of-thousands), or a "synthetic diamond" for VERY CHEAP (they make 'em for about $5 bucks a caret), depends on your "mind set", now doesn't it?

If you have any doubts:

Now, there may be idiots who like the "natural diamonds" better, but the synthetics are truly perfect and FAR superior--indeed, perfect enough to make the next generation of semiconductors from--something "naturals" are not ...

But then, it is all who you listen to--what you believe--and what you want--isn't it?

Cheap isn't always "inferior" ...

Regards, JS

Here's some pics and screenshots of the GUI:

Nice that the FFT window and scope trace windows are both viewable at the same time, I think the FFT is limited to 1MHz max frequency though, (this is a 150MS/s dual channel scope)

cheers, Jamie

Since when were we talking about diamonds? I thought we were talking electronic test equipment here...

No, but when it comes to test equipment it almost always IS.

If you are trying to say that a cheap no-name DSO (and the components used in it) is any match for a more expensive name brand DSO, then you are off with the fairies. You usually get what you pay for with test equipment.

Your analogy is as flawed as a real diamond.

Dave.

oh ya it also comes with a labview, visual basic and visual C SDK..

cheers, Jamie

That means 75MS/s per channel, yes? I also suspect that "60MHz analog bandwidth" means 30MHzx2 channels. Or it uses equivalent time sampling past a certain frequency.

We were. For once, apparently, you weren't mistaken. It serves as an "example", I am suprised you have made it this far in life without realizing such things exist. You know, like using a bowling ball and a mattress to demonstrate how gravity works ...

That may have been so, when HP ruled with excellent test equipment. Now since they have "come up" with computers, one only needs supply the proper interface and software ...

I am 55 years old (doin' the speed limit! :-) ), you must be older than my great-great-grandfather--to still hold such views ...

Regards, JS

John Smith wrote: >> [usual "come back to reality" chit]

Or, to put it simply, with a wide-band rf-amp, a high bandwidth opamp and a few ic's interfaced on a USB bus to my computer, I have the equivalent of a thousands-of-dollars-oscilloscope-of-the-90's ... all for a VERY CHEAP price!

JS

Sure, but you've missed the point, massively. I was not talking about PC based DSO's, I was talking about cheap low bandwidth asian DSO's (PC based or standalone) and how they do not have the same build quality, component quality, or performance as more expensive, better performance scopes.

No. I do however realise that the cost of an oscilloscope is not necessarily contained within the actual housing, processor and display, especially when it comes to really high performance, high quality, high bandwidth scopes which I was talking about.

I know all about PC based scopes, thanks, I designed and built my first one almost 20 years. You?

Dave.

Not sure, I think it is 150MS/s per ADC channel, here is some more info:

(cheaper on ebay!)

cheers, Jamie

No, you don't actually. How flat is the gain over frequency? How about the phase? Who's going to write the software? How do you *know* the thing works? Where's the input circuit? (RF amp = 50 ohms, did you know that?) Where are the calibrated attenuators? The time base? The trigger? How much is your time worth? Sure, you can get a USB scope for cheap now. As good as a real instrument? Nope. Handy and cheap? You bet.

I recently got the SO a 1.5 karat white gold ring. It was $800 and most of the cost was the gold in the setting.

The diamond is absolutely flawless. I know DeBeers got scared that you cannot tell the difference between their diamonds and the synthetics so they started laser etching their logo into the natural diamonds.

Diamonds are plentiful and are basically an industrial thing. They're only "worth" so much because of a clever DeBeers marketing campaign. Things are basically charcoal. They burn at 900C, did you know that?

VERY CHEAP price usually = VERY CHEAP performance.

The front end electronics is the SAME for a PC based DSO as it is for a real bench oscilloscope, or didn't you know that? You still need the ultra flat frequency and phase response, the large input range attenuator, the low noise floor, the trigger circuitry etc, etc if you want a good performance oscilloscope.

Sure you can do it "on the cheap" using off-the-shelf components as they do with most low cost pc-based DSO's, and you can even DIY. But it usually ain't going to perform as well as a purpose designed oscilloscope from one of the big names. Cheap PC based DSO's have their place, they are cheap and very handy for a lot of uses, but most of them are not high performance.

And what happens when you need greater than say 100MHz bandwidth and/ or a few hundred MHz sample rate? Doesn't get that easy then does it?

Oops, you forgot the software. Going to write that yourself are you?, ever tried? (I have).

Oops, you forgot the embedded design work. What about the VHDL (or whatever) for your FPGA and/or glue logic? Going to get that off-the- shelf are you?

Oops, you forgot the command and control protocol. Your USB chip going to magically do that for you is it?

Oops, you forgot the relays! Might need a couple of them for the front end perhaps? If not, then perhaps you can help answer the OP's original question...

What about triggering and sampling rate? real-time or equivalent?, or a combo of both? Pre and post triggering? Trigger level control and filtering?

Dave.

Yes I was aware of that, it's how they managed to make the things in the first place.