Oscium Oscilliscope

[planet10]

Originally Posted by cliffyk

The analog BW of 5MHz is bumping right up against the Nyquist limit of the sampling rate of 12MS/s. The usable bandwidth at best 1/5 of the sample rate or 2.4Mhz.

Thanx guys.

I do find the quoted statement interesting. 1/2 is to many "sufficient" for audio listening, what is it about sillyscopes that limits it to 1/5?

dave

[cliffyk]

Originally Posted by planet10

Thanx guys.

I do find the quoted statement interesting. 1/2 is to many "sufficient" for audio listening, what is it about sillyscopes that limits it to 1/5?

dave

Greatly oversimplified--the Nyquist frequency (1/2 the sample rate) is the upper limit for resolving sine waves. To accurately display faster rise time signals the sample rate needs to be a minimum of 3-4 times higher than the equivalent frequency of the rise time--5x faster is a rule of thumb, some engineers believe 10x to 20x is the proper ratio.

[digits]

I.e. a 20Mhz scope is only good for measuring 2Mhz square waves.?

[stratus46]

Originally Posted by digits

I.e. a 20Mhz scope is only good for measuring 2Mhz square waves.?

If you want to see more than the fundamental sine wave, yes.

G²

[kevinkr]

Originally Posted by planet10

Thanx guys.

I do find the quoted statement interesting. 1/2 is to many "sufficient" for audio listening, what is it about sillyscopes that limits it to 1/5?

dave

Take a look at the waveform coming out of most CD players with a test disk having a 10kHz or higher frequency sine wave recorded on it at various amplitudes and you will have your answer.

[planet10]

Originally Posted by kevinkr

Take a look at the waveform coming out of most CD players with a test disk having a 10kHz or higher frequency sine wave recorded on it at various amplitudes and you will have your answer.

I don't have anything to do that with.

dave

[planet10]

Originally Posted by cliffyk

Greatly oversimplified--the Nyquist frequency (1/2 the sample rate) is the upper limit for resolving sine waves. To accurately display faster rise time signals the sample rate needs to be a minimum of 3-4 times higher than the equivalent frequency of the rise time--5x faster is a rule of thumb, some engineers believe 10x to 20x is the proper ratio.

The jives with my belief that 44 k is insufficient for the higest auality audio.

dave

[phaselag]

Good chance with a product such as this is that performance will be sub-par. Sample rate, A/D resolution, input attenuation, etc are all not going to be par with a good oscilloscope. A good reference is that PC based scopes are really not a factor in the test equipment market, and they have a lot more computing horsepower than an ipad.

If you think you need a scope, buy a scope. Anything else is just a toy.

paul

[digits]

Well, I have seen some VERY EXPENSIVE pc based scopes claiming to go out to 200megs... but at a cost where you'd be better off buying TEK.

[cliffyk]

Originally Posted by digits

Well, I have seen some VERY EXPENSIVE pc based scopes claiming to go out to 200megs... but at a cost where you'd be better off buying TEK.

It's all in the front-end, and PicoScope is probably the only manufacturer out there making decent analog front-ends.

Most USB "oscilloscopes" have lousy voltage dividers, horribly non-linear frequency response, and are single FPGA based meaning that they are incapable of reading both channels simultaneously--though many claim they do. I keep hoping for something decent and affordable, but mostly they are toys.

As a "Lecroy guy" I lean that direction, but the Tek scopes are also great instruments...