Seems we are in a great time for electronics hobbyists wrt to
instruments.
It largley depends on where your area of interest lies. For low-speed
digital, yeah, absolutely, but for somewhat more sophisticated desires I'd
yet to see anything like:
* A USB o-scope that competes with mid-level commercial offerings.
Something like 500MHz+ bandwidth, 2+ GSps, 8 bit resolution, 4 channels,
decent triggering, etc.
* (As Joerg has mentioned on occasion) A USB spectrum analyzer with decent
bandwidth and dynamic range, e.g., 1GHz upper-end frequency, 80+ dB dynamic
range and bandwidths of, say, 3kHz or better.
* A USB TDR box.
All of these would have enough demand that I think you could make money
building them, although it's hard to say for certain. One thing that is
clear these days is that you might easily spend more time on software than
hardware, since everyone expects a nice GUI -- possibly a good reason to
build boxes like these as open-source.
The list above is ordered from "almost available" to "not at all available:"
There are plenty of USB 'scopes out there, just not with the specs listed.
There are some spectrum analzyers (even a handful of 2-port network
analyzers), but they're often sound card interfaces and hence quite
restricted in upper-end frequency. (And with both of these types of
instruments, it's very common to see the designers state that... hey!...
they're using, e.g., a 14-bit ADC and therefore they have 85+ dB dynamic
range, which very often isn't the case due to analog front-ends that don't
quite cut it.)
What PC instruments do you use and are you happy with them?
I think the USRP from Matt Ettus for use with GNURadio is a pretty cool
board. There's a *lot* of effort invested in that project.
Commercially, I like National Instruments' USB to GPIB adapter. I also like
a USB to SPI adapter I designed myself.
---Joel Kolstad