scope for hobbyist who hopes to eventually design circuits

Maybe. I like to use external USB sound cards mostly because the internal sound chips pickup plenty of digital noise from all over the computah. External is much quieter.

This is how one of my neighbors add DC to the output: Easy enough.

DC inputs are a bit of a mess. Most of the small USB dongle type cards do NOT have a stereo input and just tied the L and R input channels together. If I just short the input cap, the chip input sits at 2.23VDC, which not a good thing when I short the input to ground, and get an out of range reading. Here's one solution:

I was in a hurry to do mine, so I just installed a large value NP electrolytic cap across the coupling resistor. It takes a while to charge/discharge and settle down. I don't plan to use the sound card as a DVM, so just a bigger cap to minimize droop on the square waves and sweeps is sufficient.

More:

Sound Card DC Input Modification

Sound Card DC Measurements

USB Scope and generators etc...

I like the Rigol low end function generator too. ~$400. uH to 20 MHz. (It's got some range switching which changes the output impedance some...(@6V p-p) but not that bad.)

George H.

I've got the DG4062 60MHz dual-channel arb. LXI-C and all- awesome value!

There's some guy trying to sell a 2MHz analog ca. 1990 Kenwood FG273 for $540.00 ..

--Spehro Pefhany

Best regards, Spehro Pefhany

One problem with PC based instrumentation is the grounding issues, especially with table top PCs. These often have some connection between the signal ground and mains PE/Earth terminal, causing e.g. hum problems, especially with other peripherals connected to the same computer.

The situation is easier with laptops, since these can be operated from batteries.

So in practice, the oscilloscope input should have galvanic isolation or if some USB device is used, there should be an isolated USB connection between the USB dongle and the computer.

USB isolators are cheap, so no problem there

But, you should use it, the laptop idea is dangerous. If you connect to mains related voltages, you end up being electrocuted if you don't have the isolation

Cheers

Klaus

Dump the girlfriend and buy the scope!

How about "fancy"? Trigger on a (perhaps non-repetitive) waveform in normal manner. Then, select some defined point described via delay and some "wiggle" feature as second trigger for subsection expanded display. Show jitter of that; output to a speaker.

Or a cross-domain analyzer like those ONLY found in new-clear sardines?

Well, for simplicity, one can use a VOM (_NOT_ a DVM) to measure pulse width, pulse amplitude, rep rate, capacitor values, and other mundane things. Scope in that case is mouthwash.

More reliable and less expensive...

You might have a look at

Cheap , you probably would learn something by making one, and will work with higher frequencies than using a sound card.

And later you might have a look at

Dan