Computerized "Scope"

[jjman]

I'd like to get a scope but I know little about them. I did a search about a year ago and noticed that there seemed to be no scopes that utilize the computer screen we all already have. Are there any? Do/would they suck? Is there a reason to not have the display, say via a USB connection and software, into a PC? Maybe PCs/monitors aren’t “fast” enough or something? Just not cost effective?

[nickt]

Part of the issue is the old style scopes simply varied the horizontal sweep base and used the input signal to diflect the vertical. All analog all easy.

If you want to use your computer screen then the scope has to capture the waveform somehow because your screen sweep is fixed and much more complex (ie not just a single dot moving back and forth creating a single horizontal line).

I think there are some cards that do this stuff. They are pretty basic if I recall correctly but could be suitable for audio. The main issue is their frequency response is low (ie audio) so stuff like HF oscillation might be invisible.

Even a cheap CRT scope will go up to 2MHz or so.

BTW I don't have a scope now but used one for work for many years.

Hope this helps.

[mhuss]

There are scope add-ons available (search the web), but they tend to cost almost as much as a good used scope.

The computer ones have the advantage of having 'capture the waveform' options like a digital storage scope. They require an outboard 'pod' of some sort that the scope probes can plug into, and which buffer and attenuate the signal. The fanciers ones actually have most of a digital scope in the pod, and just use the PC for storage, control, and display.

--mark

[FUCHSAUDIO]

Good used scopes (I use an H/P 1222A that's 30+ years old and works great) are fine. Old tube Tectronix are good too, but getting harder to find.

Scope/PC things are cool, but remember; A blocking capacitor on the input ! Trying to look at a tube plate (for example) can "roast" a solid state piece of test gear. I never used a PC scope (although the idea of saving traces and making comparisons etc) does appeal to me). I would worry that the input module (whatever is used to connect it to the device under test) might be designed for low level, low voltage digital type voltages.

[tubers]

I have both an analog scope and a couple of PC based scopes. I really like the PC based scopes for the following reasons:

- easy to share with others
- spectrum analysis is quick and easy
- easy to save the pictures for diaries and log books.

I used a bitscope for a while, but now I have purchased a 4 channel 3224 from pico scope. Great for audio electronics.

[FUCHSAUDIO]

Can you explain what you use for an interface and software ?

I have both an analog scope and a couple of PC based scopes. I really like the PC based scopes for the following reasons:

- easy to share with others
- spectrum analysis is quick and easy
- easy to save the pictures for diaries and log books.

I used a bitscope for a while, but now I have purchased a 4 channel 3224 from pico scope. Great for audio electronics.

[drz400]

I'd like to get a scope but I know little about them. I did a search about a year ago and noticed that there seemed to be no scopes that utilize the computer screen we all already have. Are there any? Do/would they suck? Is there a reason to not have the display, say via a USB connection and software, into a PC? Maybe PCs/monitors aren’t “fast” enough or something? Just not cost effective?

DSO-2100 Link Instruments USB interface is the one I use but the new version is
http://www.linkinstruments.com/oscilloscope.htm

Mine does spectrum analysis as well use with Scope probes
Works great but does require more knowledge than a simple scope and is Digital. If I could only have one scope it is the Tek465B
I prefer an analog scope for trouble shooting but FFT is fun as is the storage.

[dartanion]

LabView can do a lot of this stuff and then some, but is very pricy with all the add on hardware needed. Really powerful stuff though.

[tubers]

If you buy a PC based scope, it will come with software that'll run on your PC.

Here is bitscope. They have an online demo you can play with. http://www.bitscope.com/

Here is pico scope software that comes with the pico scopes http://www.picotech.com/picoscope-oscil ... tware.html

Contrary to other opinions, with my amp repair and building I exclusively use my digital scope. I have an analog Tek 2210, but rarely use it. The digital scope captures just as fast and I can easily see a the little nuances that comes up in audio electronics.

Now that the sales pitch is over, I do have a bitscope 210 with USB adapter for sale. If you are interested $200 pm me.

[nickt]

DSO-2100 Link Instruments USB interface is the one I use but the new version is
http://www.linkinstruments.com/oscilloscope.htm

Mine does spectrum analysis as well use with Scope probes
Works great but does require more knowledge than a simple scope and is Digital. If I could only have one scope it is the Tek465B
I prefer an analog scope for trouble shooting but FFT is fun as is the storage.

Holy moley $950 flag fall then $395 for the 10x 100x probes!

Geeze you could get a used analog and build an ODS with the change! But I'm a registered cheapskate.

In any case it looks perfectly adequate for audio however they do seem to emphasise the sampling rate rather than the frequency response - digging into the "more info" it claims to be ~100MHz but separately rates the FFT as 250MHz - which leaves me scratching my head.

[d2camero]

really good point. Before I purchased my second DSO, I researched expensive Agilent and Tek scopes (like $10,000 scopes) and found their sample size to be way inadequate for decent audio work. Ultimately that is why I went with the picoscope 3424. 12bit sample size and more than enough sample rate to capture 4 channels up to 40kHz and a large enough memory for highly detailed single shots.

But as you point out, it is still expensive. $1400 can buy a lot of used analog scopes. (and half of a decent amp)

[Motörbööt]

Hi,


http://zeitnitz.de/Christian/Scope/Scope_en.html

Greetz
.

[d2camero]

This would be a great inexpensive way to start. Sound cards are great because they are made for audio circuits (16bit samples). Search google for "sound card oscilliscope" and you will find a variety of software out there.

Their bandwidth is limited, perhaps 20kHz, but will work for most of your needs. You will need to build an input buffer to test anything over a volt. Here is a schematic: http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=3428 although it only has 150V protection, although it would be nice to have 1kV protection so you don't fry you computer.

Also sound cards are supposedly decoupled from DC so any measurements coupled to DC will not be representative of the true signal (not too much of a big deal).

[drz400]

DSO-2100 Link Instruments USB interface is the one I use but the new version is
http://www.linkinstruments.com/oscilloscope.htm

Mine does spectrum analysis as well use with Scope probes
Works great but does require more knowledge than a simple scope and is Digital. If I could only have one scope it is the Tek465B
I prefer an analog scope for trouble shooting but FFT is fun as is the storage.

Holy moley $950 flag fall then $395 for the 10x 100x probes!

Geeze you could get a used analog and build an ODS with the change! But I'm a registered cheapskate.

In any case it looks perfectly adequate for audio however they do seem to emphasise the sampling rate rather than the frequency response - digging into the "more info" it claims to be ~100MHz but separately rates the FFT as 250MHz - which leaves me scratching my head.

Those are differential probes
http://www.linkinstruments.com/adf25.htm
the standard probes are $80

In reality I only use it for Spectrum stuff
I use a 465B and 2465B as a work horse

Also the DSO 2100 is discontinued and they only offered to pay me $100 for mine to upgrade so maybe they will sell a used one cheap, it is still a great unit.

[nickt]

http://zeitnitz.de/Christian/Scope/Scope_en.html

Hi Motörbööt,

From their web page.

For external sources care has to be taken, not to exceed the voltage range of the inputs. The range is usually only ±0.7V !! If higher voltage need to be analyzed, a voltage divider has to be used. Additional protection diodes are recommended in order to avoid any damage to the sound card and to the computer.

This is a real worry - my original post was basically referring to these and other cheapies - lo voltage and frankly dangerous. As someone else said - its very easy to fry the electronics (and/or your computer!!) with tube amp voltages.

Like everything else tube related support for hi voltages seems to be "niche" these days. Only a few of the USB scopes mentioned above even offered 100x probes. Most only went to +/- 50V with a 10x probe.

I guess my point is that the "exotic" features (spectrum analysis, printing...) are all very well (and fun) but they aren't the core function of a scope. If the scope inherently can't handle the normal range of inputs (and lets face it you will stick your probe on 450v DC by mistake sometime) then forget it.

my 2c anyway

cheers
Nick