Products > Test Equipment
About Picos' Sampling Rate
balnazzar:
Hi, I was look at the Pico 5000 series datasheet. These scopes do have the "usual" 1 GSa/s resolution, but here is something that caught my attention:
Maximum sampling rate (continuous USB streaming into PC memory):
USB 3, using PicoScope software: 15 to 20 MS/s
USB 3, using PicoSDK: 125 MS/s (8-bit) or 62.5 MS/s (12 to 16 bit modes)
I'd like someone knowleadgeable about Picos to explain this.. I mean, what good will the 1 GSa/s do, if the signal is processed and displayed by the software, which has access to just 15-20 MSa/s??
Of course it can't function in such a way, so I basically don't understand how a USB scope actually work.
Thanks.
voltsandjolts:
Question for you:
How much memory is in the picoscope 5000 and what is it for?
balnazzar:
--- Quote from: voltsandjolts on October 29, 2022, 11:23:31 am ---Question for you:
How much memory is in the picoscope 5000 and what is it for?
--- End quote ---
128-512M, as per datasheet. It's used for holding the stuff it acquires, and it's obviously related to the sampling rate.. Since the software resides on a PC with virtually unlimited memory, I'd expect the sampling rate of a USB scope to be the same or higher (if the ADC allows) with respect to a standalone scope.
balnazzar:
Here is another noob-ish observation: more memory depth means that the scope can be slow under certain conditions if it hasn't enough processing power. But again, on a usb scope much of the processing is done by the pc, that has much more processing power than a standalone scope.
jasonRF:
--- Quote from: balnazzar on October 29, 2022, 11:03:51 am ---Hi, I was look at the Pico 5000 series datasheet. These scopes do have the "usual" 1 GSa/s resolution, but here is something that caught my attention:
Maximum sampling rate (continuous USB streaming into PC memory):
USB 3, using PicoScope software: 15 to 20 MS/s
USB 3, using PicoSDK: 125 MS/s (8-bit) or 62.5 MS/s (12 to 16 bit modes)
I'd like someone knowleadgeable about Picos to explain this.. I mean, what good will the 1 GSa/s do, if the signal is processed and displayed by the software, which has access to just 15-20 MSa/s??
Of course it can't function in such a way, so I basically don't understand how a USB scope actually work.
Thanks.
--- End quote ---
You can run the picoscopes in two modes. One is the traditional block mode where the on-board memory is used to store the captures, so you are limited to that memory depth. This mode allows for the highest sample rates. But there will be time gaps between the sampled waveforms. I believe most scopes work like this.
The second mode is streaming mode, which continuously streams samples from the acquisition system to the pc. But you cannot do this at the highest sample rates. If you write your own code using the picoSDK API, you get the 125 MS/s and can stream for hours on end if you know what you are doing when you code it up. But you can also stream using Picoscope6 software (not sure it is in picoscope7 yet), and this is at the lower rate od 15-20 MS/s. But the picoscope6 software only has a 100 MSample buffer to handle streaming.
So it makes no sense to use streaming mode inside the picoscope software with models that have more than 100 MSamples of memory.
I have used streaming inside picoscope6 with my 2204a - it gives me 100 MSamples at 1 MS/s - so can be useful for catching weird behavior in audio curcuits. But unless I write my own code in picoSDK I will never use streaming mode with my 5244b.
Jason
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