USB digital scope

[Jamie Morken]

Hi,

I just bought a USB digital oscilloscope (DSO-2150 150MS/s)
off ebay and I was kind of surprised that it has relays in
it for the voltage division selection. Do standalone digital
scopes (with rotary encoder knobs) also have relays for this
or is there a solid state way to select the voltage division?

cheers,
Jamie

 

[John Larkin]

Hi,

I just bought a USB digital oscilloscope (DSO-2150 150MS/s)
off ebay and I was kind of surprised that it has relays in
it for the voltage division selection. Do standalone digital
scopes (with rotary encoder knobs) also have relays for this
or is there a solid state way to select the voltage division?

cheers,
Jamie

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

John

 

[[email protected]]

Hi,

I just bought a USB digital oscilloscope (DSO-2150 150MS/s)
off ebay and I was kind of surprised that it has relays in
it for the voltage division selection. Do standalone digital
scopes (with rotary encoder knobs) also have relays for this
or is there a solid state way to select the voltage division?

cheers,
Jamie

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.

 

[[email protected]]

Hi,

I just bought a USB digital oscilloscope (DSO-2150 150MS/s)
off ebay and I was kind of surprised that it has relays in
it for the voltage division selection. Do standalone digital
scopes (with rotary encoder knobs) also have relays for this
or is there a solid state way to select the voltage division?

cheers,
Jamie

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

 

[David L. Jones]

Hi,

I just bought a USB digital oscilloscope (DSO-2150 150MS/s)
off ebay and I was kind of surprised that it has relays in
it for the voltage division selection. Do standalone digital
scopes (with rotary encoder knobs) also have relays for this
or is there a solid state way to select the voltage division?

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.

 

[D from BC]

Hi,

I just bought a USB digital oscilloscope (DSO-2150 150MS/s)
off ebay and I was kind of surprised that it has relays in
it for the voltage division selection. Do standalone digital
scopes (with rotary encoder knobs) also have relays for this
or is there a solid state way to select the voltage division?

cheers,
Jamie

Open it up and post a picture of the pcb.


D from BC
British Columbia
Canada.

 

[John Smith]

...

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:

http://www.wired.com/wired/archive/11.09/diamond.html

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

 

[Jamie Morken]

Open it up and post a picture of the pcb.

Here's some pics and screenshots of the GUI:

http://rocketresearch.nekrom.com/new/DSO-2150 USB oscilloscope /

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

 

[David L. Jones]

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?

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

If you have any doubts:

http://www.wired.com/wired/archive/11.09/diamond.html

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" ...

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.

 

[Jamie Morken]

Open it up and post a picture of the pcb.


D from BC
British Columbia
Canada.

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

cheers,
Jamie

 

[[email protected]]

Here's some pics and screenshots of the GUI:

http://rocketresearch.nekrom.com/new/DSO-2150 USB oscilloscope /

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)

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.

 

[John Smith]

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

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 ...

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

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 ...

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.

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]

[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

 

[David L. Jones]

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 ...

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.

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

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.

 

[Jamie Morken]

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.

Not sure, I think it is 150MS/s per ADC channel, here is some more info:
http://www.partsforhdtv.com/pcbased-usb-digital-storage-oscilloscope-dso2150-p-247.html

(cheaper on ebay!)

cheers,
Jamie

 

[[email protected]]

[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

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.

 

[T]

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:

http://www.wired.com/wired/archive/11.09/diamond.html

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

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.

 

[[email protected]]

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?

 

[David L. Jones]

[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!

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.

 

[T]

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?

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