o-scope question

[mixedgas]

I've tested the velleman. The 8 bit resolution is actually 6 bit, useless for laser.

problem with sound card scopes is they are sampling at the same rate laserboy is displaying at, so you'll get aliasing.

it costs beaucoup bux, but go with a picoscope if you must have software scope.

Parallax tech has one for 110$ , but its max rate is 100 khz, so on a 48 Ksamp second waveform, your pushing it, and on a 96 khz sound card, your toast.

This is one case where even a 1 mhz CRT based scope is really cost effective.

Nyquist's rule says you need to sample at a minimum of just over two times the max frequency of your waveform, and people who do this in practice will tell you 4-6 times for a digital scope, as many anti-aliasing filters in the scopes are poor at best.

Make sure whatever you buy has triggered sweep, or you will watch your laser waveforms "march" left or right across the screen. This is very annoying.

It will show up on the scopes control panel as a "Sweep Level" control. Or a "trigger" knob in the timebase.


Steve

[The_Doctor]

I've tested the velleman. The 8 bit resolution is actually 6 bit, useless for laser.

Ok. That's no good then. Maybe eOscope is worth a look though, for small handheld LCD type. It's DIY though. I only mentioned this because they're small and portable. My earlier post covered what I think is the right way to go.

[drlava]

Don't forget you can use my 'max.wav' I posted earlier for sound card DAC tuning without a scope, only a multimeter.

[gf8stiv3]

the software scopes I have seen don't let you do X/Y mode but then again I haven't looked in some time

I picked up a BK scope for $60 shipped, and found another one for parts for $10 local, does display the dac images pretty nicely.

FYI, there is a following of people making scopes out of soundcards I thought about doing that to mess with James...Picture it, sound card DAC hooked to soundcard scope displaying laser boy image on computer screen hmmmmm, hope I started something here lol

Only reason I stayed away from that was the input voltage was rated far too low for what I needed it for originally.

[carmangary]

Does anyone know anything about these:

http://cgi.ebay.com/OWON-portable-7-...3A1%7C294%3A50

It's affordable, small, and has some nice features. The main drawback is it only goes up to 25MHz but that is good enough for most applications. I like that it can work off of a battery and has a USB port for PC data acquisition.

[mixedgas]

It has fair to good recommendations on sci.electronics.design, but according to those who have bought them, the serial/usb module costs extra, the backlight is dim,its best used in bright light, and the voltmeter function has its own inputs, ie its signal doesn't come in on the scope probes.
Also no FFT.

most buyers reccomend their next model up, which supposedly has a much better lcd.

Steve

[carmangary]

Thanks. I wouldn't mind trading in my Tex 7603 for something like that. I love the 7603 but it's so BIG!

[keeperx]

ok i lost that auction
can someone who know about this stuff find me a good o-scope deal?
im looking for the cheapest thing that will do what i need it to do..

[carmangary]

I found mine on craigslist. I see them there from time to time. Try looking locally because there will be less people fighting to get them. Any deal on Ebay gets looked over by thousands. Also, oscopes (that you can afford) are big and heavy so you don't really want to have to ship one anyway.

[gf8stiv3]

I found mine on craigslist. I see them there from time to time. Try looking locally because there will be less people fighting to get them. Any deal on Ebay gets looked over by thousands. Also, oscopes (that you can afford) are big and heavy so you don't really want to have to ship one anyway.

If your a craigslist junkie like me...check out craigshelper.com Lets you search many citys at once, instead of having to go to each one individually