Products > Test Equipment
Oscilloscope input noise comparison
rsjsouza:
--- Quote from: lordvader88 on October 26, 2018, 03:16:13 am ---can someone tell me and others that don't know, the basics here, whats the graph mean ? whats good/bad ?
--- End quote ---
lordvader88, there are many references around on the web.
A training:
https://training.ti.com/ti-precision-labs-adcs-high-speed-SNR-NSD
An article:
http://www.ni.com/white-paper/3304/en/
Hagrid:
--- Quote from: Andreas on October 25, 2018, 09:04:25 pm ---Hello,
first measurements of PicoScope 5444A
[...]
--- End quote ---
Thanks a lot! I was looking for exactly this data. Please someone correct me if I am wrong, but is the noise of the 5444 about five to ten times higher than the noise from the cheap Chinese scopes from the first page?
This makes little sense to me, since it has modes up to 16 bit resolution.
I would really appreciate it if somebody could explain this to me, thanks :).
Greetings, Hagrid
MrW0lf:
--- Quote from: Hagrid on October 30, 2018, 07:18:59 pm ---I would really appreciate it if somebody could explain this to me, thanks :).
--- End quote ---
Picos just do not have low input ranges.
2000 ±20mv to ±20v
4262 ±10 mV to ±20 V
5000 ±10 mV to ±20 V
If think in divs then 2mV/div is lowest for 5000.
Is it a problem? Depends on application. When can average, do FFT etc then noise drops quite good:
https://www.eevblog.com/forum/testgear/fft-spectrum-analysis-reviewed/
https://www.eevblog.com/forum/testgear/cheap-chinese-ad584-voltage-reference-legit-cal-data-let_s-find-out!/msg1154930/#msg1154930
https://www.eevblog.com/forum/testgear/picoscope-2000/msg1155735/#msg1155735
egonotto:
Hallo,
@Hagrid:
"I would really appreciate it if somebody could explain this to me, thanks"
You are right, the noise of the 5000 serie is not that good.
https://www.picotech.com/support/topic16031.html
But in some cases you can lower the noise.
https://www.eevblog.com/forum/testgear/looking-for-a-dynamic-signal-analyzer-with-extended-bandwidth/?all
You can limit the bandwith and lower the noise. To limit the bandwith with the 5000 series you have different ways.
From PicoScope 6 help:
"Resolution enhancement is a technique for increasing the effective vertical resolution of the scope at the expense of high-frequency detail. In some scope operating modes, PicoScope may reduce the number of samples available to maintain display performance.
For this technique to work, the signal must contain a very small amount of Gaussian noise, but for many practical applications this is generally supplied by the scope itself and the noise inherent in normal signals.
The resolution enhancement feature uses a flat moving-average filter. This acts as a lowpass filter with good step response characteristics and a very slow roll-off from the pass-band to the stop-band."
You can limit the bandwith to 20 MHz
With math you can average to lower the noise.
Best regards
egonotto
Andreas:
--- Quote from: egonotto on October 30, 2018, 09:52:10 pm ---
With math you can average to lower the noise.
--- End quote ---
Hello,
you can also directly configure the low pass frequency of a software filter in the menu.
--- Quote from: Hagrid on October 30, 2018, 07:18:59 pm ---
Please someone correct me if I am wrong, but is the noise of the 5444 about five to ten times higher than the noise from the cheap Chinese scopes from the first page?
This makes little sense to me, since it has modes up to 16 bit resolution.
--- End quote ---
I guess with a 0.5mV/Div range and only 8 Div instead of 10 the factor of 5 can be explained.
At least for that what I measure I do not need high bandwidth and high resolution at the same time.
With a software filter of 1 MHz or below (besides the hardware 20 MHz filter) the noise decreases significantly.
with best regards
Andreas
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