TV based oscilloscope

[gargmuneet]

Hello Frndz,

i want to use my TV screen as an osciloscope display. Plz give some help for this....

Thanks.

 

[House0Fwax]

You'd be much better off using your pc instead.

However, Googling "TV oscilloscope", brings up lots of dangerous modifications that you can make.... None of which are recommended.

Googling "PC oscilloscope" is a much better idea.

 

[Nigel Goodwin]

Buy a scope! - there's no decent, reasonably priced, way to use a TV as a scope.

 

[cadstarsucks]

Hello Frndz,

i want to use my TV screen as an osciloscope display. Plz give some help for this....

Thanks.

For what frequency range? There is PC scope software performs A/D on the audio card.

D.

 

[Sceadwian]

Actually, the A/D is already done in the audio card, all the software does is scale the results and display them. PC audio cards go up to 190khz sampling rates at 8/16 and some 24 bits. You can use simple attenuation circuitry to scale the input voltage range you're looking for but PC sound cards are usually capacitivly couples so you're out of luck if you want to monitor a signal that has a significant DC component. PC sound card scopes will do in a pinch, but if you really want to play with a scope there's no excuse but to go out and buy one. Even a 10 year old model off e-bay for 50 bucks or so. A lot of sound cards have built in gain stages though (for microphones) that usually provide 20db or so of gain which gives you some really good sensativity for low level signals. The upper voltage limit on the input of a sound card is around 1 or 2 volts tops, it can be attentuated internally to some degree but I don't know how that effects the A/D conversion accuracy and noise floor.

 

[cadstarsucks]

Actually, the A/D is already done in the audio card, all the software does is scale the results and display them. PC audio cards go up to 190khz sampling rates at 8/16 and some 24 bits. You can use simple attenuation circuitry to scale the input voltage range you're looking for but PC sound cards are usually capacitivly couples so you're out of luck if you want to monitor a signal that has a significant DC component. PC sound card scopes will do in a pinch, but if you really want to play with a scope there's no excuse but to go out and buy one. Even a 10 year old model off e-bay for 50 bucks or so. A lot of sound cards have built in gain stages though (for microphones) that usually provide 20db or so of gain which gives you some really good sensativity for low level signals. The upper voltage limit on the input of a sound card is around 1 or 2 volts tops, it can be attentuated internally to some degree but I don't know how that effects the A/D conversion accuracy and noise floor.

I know about the A/D...it was the AC coupling that I was not sure about. I figured the high end was 25KHz or more but was not sure about the low end.

D.

 

[Sceadwian]

I just checked quickly the output from my soundcard on a scope, it is definitly AC coupled, and even with the 96khz sampling rate (highest my card will go) it looks like there's still a lowpass filter with a cutoff of about 24khz. Seems like the only thing the higher sampling rate does is make the output much smoother at the higher frequencies. I'm going to asume the same thing applies to the inputs as well but I don't have a frequency generator to test it with.

 

[Nigel Goodwin]

This has all rather drifted away from the question though! - using a TV as a scope!.

 

[NetHopper]

I know about the A/D...it was the AC coupling that I was not sure about. I figured the high end was 25KHz or more but was not sure about the low end.

On lower end, many sound cards (probably should exclude the onboard ones) support frequency as low as 1 Hz. Normally this is not stated in their specification. But you can test it by yourself (e.g. loopback its output to input).

on higher end, for example, SoundBlaster XtremeGamer (**broken link removed**) supports 46 kHz for input.

Some sound cards may have even lower and/or higher frequency bandwidth.