Products > Test Equipment
PicoScope 2000
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MrW0lf:

--- Quote from: _Wim_ on November 06, 2018, 08:31:28 pm ---Were you able to install both PS5 and PS6 on 1 pc?

--- End quote ---

Yes but something is little weird with some PS6 menus now. However I have windows GUI scaling on and just installed some Win patches also so dunno. Functionally both seem to work as far as messed with so far. In itself PS5 is of course very crude compared to PS6. I point attention to this mainly so people would notice and perhaps some good stuff would be resurrected due to public demand.

_Wim_:

--- Quote from: MrW0lf on November 06, 2018, 08:38:26 pm ---
--- Quote from: _Wim_ on November 06, 2018, 08:31:28 pm ---Were you able to install both PS5 and PS6 on 1 pc?

--- End quote ---
I point attention to this mainly so people would notice and perhaps some good stuff would be resurrected due to public demand.

--- End quote ---
Good idea, I was very supprized to hear they use to have a "normal" persistance mode, this is one thing I find much better on my Rigol than on the Pico. The current implementation I find useless for my kind of work.
MrW0lf:
PS6 lacks wfm - wfm timing measurements so must invent own, heres unsigned delta(ChX,ChY) to avoid hassle with cursors:

ChB=1MHz sine, ChC=1MHz square, ~45° phase. Measurement matches cursors. Operating in good conditions (no noise).


ChB=1MHz sine, ChC=1MHz sine, ~15° phase. Additional function plots delay graph. Graph little corrupted by noise. DC average on non-plotting function is more accurate.


ChB=1MHz sine, ChC=1.01MHz sine. Graph gives general picture.


To avoid noise issues it may make sense to lower sampling rate, apply resolution enhancement, filter etc. I just demonstrated default situation.

Math for non graphing (PWM):
((((atan(1/tan(pi*(B/10000)))/pi)+(B/10000))*-((atan(1/tan(pi*(C/10000)))/pi)+(C/10000)))+0.25)*(1/freq(C))

Math for graphing version:
duty((((atan(1/tan(pi*(B/10000)))/pi)+(B/10000))*-((atan(1/tan(pi*(C/10000)))/pi)+(C/10000))))*(1/200)*(1/freq(C))

It works by finding zero crossings which results in PWM which can be further processed and graphed using duty(x).
jasonRF:
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).   
- 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.
- 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.
- 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...
- serial decoding but shallow memory can limit usability
- high-resolution mode to get up to 12 effective bits
- equivalent-time sampling up to 2 GS/s for periodic signals
- 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.   
- 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.
- 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). 
- 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.
- 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.
- 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.
- No external trigger input, so if you need one you must use one of the channels, and hence this becomes a one-channel scope. 
- 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.
- 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  |O
- No trigger output

For 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
jasonRF:
As a follow-up, here are a few measurements of the 2204a so support a couple of the statements I made in the last post. 

The first image is a rise-time estimate of the analog front-end.  A BK Precision 4013DDS function generator is the source, using a BNC coaxial cable and a 50-Ohm feed-through adapter at the scope input.  Rise time is shorter than 11 ns, so front-end bandwidth is at least about 32 MHz.  EDIT: this example is the best-case I found, but 12 ns is a safe upper-bound so perhaps 29 MHz is a better number.  In any case, >25 MHz seems like a safe statement given these and other measurements I've made. 

The second image is a plot showing the issue with the square-wave of the built-in signal generator.  Here I am using persistence mode, so the jitter is clearly visible. 

EDIT: decided to add a third image to show the free FRA4Picoscope app at work. This example is a passive first-order low-pass filter.  I find this app to be very useful at times, although the 600-Ohm output impedance of the signal generator is a little high for some circuits.  When that matters I add a low-output-impedance buffer between the signal generator and the device under test. 


jason
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