I know this thread is old, but it seems like the best place to post this.
This is a short review of the
Picoscope 2204a, which I think is a reasonable, inexpensive entry-level USB oscilloscope for folks that don't require larger bandwidths for their signals of interest. It currenly sells for $165 (US), although when I purchased mine in the 2015/2016 time-frame it was $139 (US). Mine is made in the UK, so that probably does add a little to the price over what it might cost if it were produced in a less expensive country. The picotech.com web site has all the specs, but the short-form is
2-channel, 8-bit, 100 MS/s (down to 50 MS/s with both channels running), 10 MHz nominal bandwidth, 35 ns rise-time, 8 ksample total memory. Includes built-in signal generator that operates up to 100 kHz for sinusoids, and 4V peak-to-peak into high-impedance loads.
I have only used the Picoscope software under Windows, so all comments are in that context.
Features I like-
Analog front-end operates like a real scope - when vertical setting is changed in Picoscope software the front-end does change gain/attenuation. No digital zoom! My unit has around 220 levels full-scale at each setting (about 7.8 bits).
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actual hardware bandwidth higher than spec - my unit has at least 25 MHz bandwidth based on both rise/fall time measurements and direct bandwidth measurements.
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Low-budget scope uses high-budget software - since Pico uses same software for all models it is polished and feature-rich. It only disables settings that the attached hardware doesn't support; nothing is disabled for marketing reasons. So the 2204a has tons of features that most budget usb scopes lack. Some are below.
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Lots of fancy math included - such as user-defined high-pass/low-pass/band-pass/band-stop digital filters, etc. Other posts on this thread show quite complicated math...
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serial decoding but shallow memory can limit usability
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high-resolution mode to get up to 12 effective bits-
equivalent-time sampling up to 2 GS/s for periodic signals
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built-in signal generator provides frequency response analysis (aka Bode plots) up to 100 kHz. You do need to download the free FRA4picoscope app for this.
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user-defined keyboard shortcuts to make operation efficient. For example I use left/right arrow keys to adjust time-base, so isn't any harder than using a knob.
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small physical size - so easy to shove in a drawer when not in use. This is the primary reason I purchased it instead of a used full-size scope.
The 2204a is a low-budget device with many limitations that are obvious from the spec sheet, and some that are not spelled-out (although some come to light if you read this entire thread).
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Signal generator actually isn't very good. Sure, it is fine for sinusoids up to 100 kHz so works for Bode plots, and is good for square waves up to a few kHz. However, it has some flaky jittery performance for square-waves at 10-ish kHz that are much worse than expected based simply on the loss of Fourier components.
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Lacks automated measurements of time/phase delay between channels - this is a serious oversight in my opinion. It is just software, and it is weird that Pico neglects it in the current version.
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FFT is less useful than you might think - because it is limited to 4k samples, and also won't display any frequencies beyond the nominal 10 MHz bandwidth of hte unit.
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No external trigger input, so if you need one you must use one of the channels, and hence this becomes a one-channel scope.
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minimum vertical setting is 10 mV/div - so if you look at small signals all the time this is not the scope for you. At least this is a real setting, though, as some manufacturers seem happy to advertise small vertical settings that require digital zoom.
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No vertical offsets - channel B has a maximum of 50 MS/s sample rate, even if it is the only channel enabled. This doesn't actually limit performance since channel A can just be used when need the full sample rate, but it can be inconvenient.
Was just playing with the 2204A and this is wrong. With just B enabled I get 100 MS/s. I've had this thing for years and somehow had this wrong impression for awhile
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No trigger outputFor similar or less money than the 2204a you can certainly get more capable hardware (more bandwidth, higher sample rates, external trigger, more memory, usb isolation, etc), but seldom will get a signal generator with associated Bode plots, and in all cases I'm aware of you will get less polished and/or capable software. That is the trade, and of course there is no one-size-fits-all 'best' option.
The primary reason I will eventually upgrade is because I want at least 100 MHz bandwidth. Unfortunately, 100 MHz Picoscopes start at $809 (US), which is too rich for me.
jason