diyAudio

diyAudio (https://www.diyaudio.com/forums/index.php)
-   Equipment & Tools (https://www.diyaudio.com/forums/equipment-and-tools/)
-   -   Oscilloscope versus usb card? (https://www.diyaudio.com/forums/equipment-and-tools/360218-oscilloscope-versus-usb-card.html)

r_jik45 15th September 2020 07:24 PM

Oscilloscope versus usb card?
 
Oscilloscope capability is expressed in MHz (20MHz .. 100MHz, etc.), usb acquisition card working as oscilloscopes have their capability expressed in samples/s, as far as I understood.
Is there a direct relationship between samples/s and MHz?

If the usb card acquisition is let's say 100ks/s, does it mean 100KHz? Kind of low compare to simple/old oscilloscopes rated for 5-10MHz.

Not having an oscilloscope, I am interested in the two following items:
- EspoTek Labrador Board (EspoTek Labrador – Official EspoTek Online Store),
- iCP12B - usbStick (iCP12B (1mV+) - usbStick (Micro USB DAQ, PC Oscilloscope, Data Logger, Frequency Generator, PIC18F2553 IO Board)).
Any member tried them?
How do you think they compare versus simple low end oscilloscopes?

edbarx 15th September 2020 08:09 PM

A waveform is a continuous locus of points. This means in theory an infinite number of samples is required. In reality, this is not possible, so we have to be contented with less points to describe a waveform. The more complex a waveform is the more points are required. If the waveform is known less points are required and extrapolation can be used.

So, the answer is it depends on what signal you want to display.

jjasniew 15th September 2020 08:17 PM

>Is there a direct relationship between samples/s and MHz?

Theoretically, you want at least 2 samples per Hz, but I prefer 10. 10 is an easy number; if the channel samples at 1MHz, it's good for capturing a useful waveform up to 100KHz. Should be plenty good for audio waveforms.

The scope as a unit - versus a card or stick - has the advantage that it's a monolithic device; it'll still be available when you upgrade laptop / operating system. How many USB devices can you count that are now garbage because the manufacturer decided - for whatever reason - not to support "windows 10" drivers?

Vovk Z 15th September 2020 08:30 PM

Quote:

Originally Posted by r_jik45 (https://www.diyaudio.com/forums/equipment-and-tools/360218-oscilloscope-versus-usb-card-post6342445.html#post6342445)
How do you think they compare versus simple low end oscilloscopes?

Oscilloscope is almost always better then USB-oscilloscope (much convenient).

Vovk Z 15th September 2020 08:33 PM

For a clean sine wave signal one Mps is 0.5 MHz. But for real life signals you need at least 10 Mps for 1 MHz (to it was comparable with old analog oscilloscope).

H713 15th September 2020 11:16 PM

Even for audio work, you need more than 100 kHz bandwidth, ideally at least. I've seen many amplifiers oscillate above 5 MHz, and that includes tube stages. Op-amps can do it too.

I recently had a MOSFET amplifier that went into a fairly violent 15 MHz oscillation. So a real 20 MHz oscilloscope is sort of a minimum. You can get away with a sound card, but an analog oscilloscope can be picked up pretty cheap these days and is definitely a big improvement.

r_jik45 16th September 2020 07:02 AM

Thanks for the comments so far.
Looks like usb cards are not much recommended.

SemperFi 16th September 2020 07:38 AM

There are cheap PC scopes with 100MSPS and more. They are mostly 8bit resolution so not the best for low level probing. Soundcards may have very low bandwidth but they have 16bit or more resolution.
But detecting hf oscillations and other details are most important imo. Besides a pc scope has a more practical interface and handles higher voltages than a usb soundcard.

jan.didden 16th September 2020 07:43 AM

I have a 1GHz 'usb scope', and I think that a 1GHz 'real' scope will be at least as expensive, probably more.

If you are starting with scopes, you will need some time and activity to get up to speed and comfortably with such a piece of equipment; there's much more than just looking at a sinewave.
So in that case you are better off with a traditional scope because you don't need the added complexity of learning software while also learning to use a scope.

After you get some experience you can decide how to move forward, you will know what you really need.

Again, in that case you'd be better off with starting on a used 200 or 300MHz MHz Tek or Agilent as they are available for a few 100 dollars.

Ohh, and get a 4-channel instead of a 2-channel if you can. You always need more channels to look at different points in your circuits.

Jan

r_jik45 16th September 2020 09:25 AM

Thanks for your comment Jan.

In point of fact I was using oscilloscopes for my work. Had an old one at home too but had to discard it after years of no-use while abroad. Using one is not a problem I think.
Was using acquisition cards/softwares too at work.

Now it's for private use. Saw several usb-based scopes on the net. Wondering where to spend the money, and why specifications are not expressed the same way (Hz v. samples/s).

4 channels instead of 2. Can become handy. 2 channels in the labrador board.


All times are GMT. The time now is 08:15 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 17.65%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Copyright ©1999-2020 diyAudio

Wiki