FWIW, I have gotten yeoman service from my Sekusui scope. 20 years with no problems.
A sound card/software is no substitute for a scope, but it's a dandy substitute for a sine wave generator and spectrum analyzer (square waves are best handled by a good function generator). One other nice thing to have is a wave analyzer like the HP 3581A. It doubles as an AC voltmeter and a good spectrum analyzer to cross-check soundcard measurements.
A sound card/software is no substitute for a scope, but it's a dandy substitute for a sine wave generator and spectrum analyzer (square waves are best handled by a good function generator). One other nice thing to have is a wave analyzer like the HP 3581A. It doubles as an AC voltmeter and a good spectrum analyzer to cross-check soundcard measurements.
Two things to know about oscilloscope bandwidth:
Firstly, bandwidth is quoted at -3dB points, so your 20MHz oscilloscope is actually -3dB at 20MHz and only really any good at measuring (1% error) at 2MHz.
Secondly, the bandwidth also tends to determine the fastest speed of the time base. For example, my 10MHz Gould has a fastest time base setting of 1us/div, but my 60MHz Tek goes down to 50ns/div. One cycle of 1MHz is 1us, so the Gould doesn't allow you to see much detail on a 1MHz waveform, whereas the Tek allows you to fill its screen (ten divisions) with a 2MHz waveform. The significance of seeing detail is that if you have an oscillating amplifier and do something that changes the shape or amplitude of the waveform, you're getting nearer to the cause of oscillation, and therefore nearer to curing it.
Oh, and a third thing: You can't have too much oscilloscope bandwidth.
Firstly, bandwidth is quoted at -3dB points, so your 20MHz oscilloscope is actually -3dB at 20MHz and only really any good at measuring (1% error) at 2MHz.
Secondly, the bandwidth also tends to determine the fastest speed of the time base. For example, my 10MHz Gould has a fastest time base setting of 1us/div, but my 60MHz Tek goes down to 50ns/div. One cycle of 1MHz is 1us, so the Gould doesn't allow you to see much detail on a 1MHz waveform, whereas the Tek allows you to fill its screen (ten divisions) with a 2MHz waveform. The significance of seeing detail is that if you have an oscillating amplifier and do something that changes the shape or amplitude of the waveform, you're getting nearer to the cause of oscillation, and therefore nearer to curing it.
Oh, and a third thing: You can't have too much oscilloscope bandwidth.
Hi EC8010,
Good points. I think the average guy will get great service from a new 20 MHz 'scope. Those time bases were running 0.5 uS last time I looked, you might even find a 0.2 uS model. They run about $500 ~ 600 CDN, new. For analog work you will need a smoking hot digital scope in order to see the same detail as an analog scope. Way back when, the only DSO I could even see a CD eyepattern with was the $8,000 HP (then) models. The rest couldn't display the pattern. No problem with the cheaper analog 'scopes, and I mean cheap.
-Chris
Good points. I think the average guy will get great service from a new 20 MHz 'scope. Those time bases were running 0.5 uS last time I looked, you might even find a 0.2 uS model. They run about $500 ~ 600 CDN, new. For analog work you will need a smoking hot digital scope in order to see the same detail as an analog scope. Way back when, the only DSO I could even see a CD eyepattern with was the $8,000 HP (then) models. The rest couldn't display the pattern. No problem with the cheaper analog 'scopes, and I mean cheap.
-Chris
o-scop and function gen adapter for sound card
i posted a design for function gen and o-scope adapter in the other stuff>everything else forum. should be good enough for general stuff, but i'll work on a downconverter for stuff above 50khz...... just remembered, i should add an ac coupling function to the adapter too.... one of those DUHH! moments.....
voltage ranges go from 1000:1 to 1:1 with a buffered output, and about a 1M input impedance (actually 500k, now that i calculated it out, so that's something else i can change by recalculating the 100:1 divider).
once i get the 1% resistors and 10 turn trimmers assembled, i'll build one.
i posted a design for function gen and o-scope adapter in the other stuff>everything else forum. should be good enough for general stuff, but i'll work on a downconverter for stuff above 50khz...... just remembered, i should add an ac coupling function to the adapter too.... one of those DUHH! moments.....
voltage ranges go from 1000:1 to 1:1 with a buffered output, and about a 1M input impedance (actually 500k, now that i calculated it out, so that's something else i can change by recalculating the 100:1 divider).
once i get the 1% resistors and 10 turn trimmers assembled, i'll build one.
cviller said:
First...thanks a lot for all this posts!
I want to quote that reply because i've checked that website out and i'm not in complete agreement.
The price, if i'm not wrong, is abour $200 for the best.
It is a scope-meter...just a good fluke would cost more than that and then a discrete digital tek would cost much more than that.
It seems convenient to me...but there would be something that i don't cach..and that's why i'm posting.
Could anybody help me to see the inconvenients?
how much would i have to spend to have a better equipment?
Since i've never owned a scope and so it would be my first laboratory,in order to connect my thoughts to the EC's previous post, i don't need something super refined i just need to start out.
I would like to spend the right amount....and own equipments that would serve to me for a long time and which i could start to build something and to make some measurements.
But at the same time i dont want to spend $200-300 and then later on...realize that i have made a wrong purchase regreat and then replace those things because insufficient.
i don't know if i was able to explain my self....
hope yes...
Could anybody help me out to find the right scope distortion analyzer and meter for a noobies...but something that would serve for a long time.
I would go for the PC solution....i think so....
hope to receive some good advice.
i've just seen this digital multimeter FLUKE 110 at $89.
http://www.mcminone.com/
is it a good price? is it a good multimeter?
http://www.mcminone.com/
is it a good price? is it a good multimeter?
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