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Pocket-Sized 6 GHz 1 TS/s ET Scope

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SJL-Instruments:

--- Quote from: joeqsmith on February 02, 2024, 06:55:18 pm ---Thank you very much for supplying those valuable tips!! 

--- End quote ---
We've added these notes to the next manual revision as well.


--- Quote from: joeqsmith on February 02, 2024, 06:55:18 pm ---Before working with the internal trigger, I would want to implement your other correction as I assume the internal trigger is considered low.

--- End quote ---
Could you clarify what you mean by "the internal trigger is considered low"?
We'll send you a pre-release version of the software today or tomorrow that implements the DC offset trim.


--- Quote from: joeqsmith on February 02, 2024, 06:55:18 pm ---Showing the same 4 sets of data for channel 3.   White was the initial testing from post 197,  Red was repeating this test prior to reworking the board, Green was taken when the scope was cold right after rework and Blue was after 3 hour warmup after rework. 

I am using the absolute values to provide you with a better view of the gain and offset as well as the different in noise levels between the positive and negative apex.   Note that noise is still higher in the positive region.  Maybe a bit of noise on one of the supplies.  Maybe it's normal.  It has always been there and guessing what aggravates the glitches. 

--- End quote ---
Thanks again for supplying this data. The noise from this plot is considered within specification - RMS deviation from mean waveform should be ~1 mV or lower. The zero-crossings are within the ±50 ps (±20 ps typ) global timebase shift specification.


--- Quote from: joeqsmith on February 02, 2024, 07:42:44 pm ---Just to make sure, using your example from 4.3.3, the CDF for the fit voltage would be 0.500 which is within your 0.27&0.75 criteria, meaning use the Gaussian fit rather than interpolation?   

--- End quote ---
First compute the 0.25 and 0.75 percentile from the CDF using the interpolation method (i.e. the first and third quartiles in voltage). In this case, this would be at 0.474V and 0.477V. The check is to verify that the voltage obtained from the Gaussian error function lies within these two bounds.

joeqsmith:

--- Quote from: SJL-Instruments on February 02, 2024, 09:27:37 pm ---
--- Quote from: joeqsmith on February 02, 2024, 06:55:18 pm ---Before working with the internal trigger, I would want to implement your other correction as I assume the internal trigger is considered low.

--- End quote ---
Could you clarify what you mean by "the internal trigger is considered low"?

--- End quote ---

Your initial comment was:

--- Quote ---This only matters at low triggers/sample or samples/cdf, when the data is very noisy and the fit might blow up.
--- End quote ---

You didn't define "low", but the manual states:

--- Quote ---When no trigger is present, the scope will trigger off its internal clock (100 Mtrig/s) until a valid trigger source returns.
--- End quote ---
and also:

--- Quote ---The main limitation of the CDF sampling technique is for signals with infrequent trigger opportunities (500 ktrig/second or lower).
--- End quote ---

By low, did you mean < 500ktrig/sec?  If so, internal trigger does not fall into that category? 
 


--- Quote ---Thanks again for supplying this data. The noise from this plot is considered within specification - RMS deviation from mean waveform should be ~1 mV or lower. The zero-crossings are within the ±50 ps (±20 ps typ) global timebase shift specification.

--- End quote ---

Thanks.


--- Quote ---
--- Quote from: joeqsmith on February 02, 2024, 07:42:44 pm ---Just to make sure, using your example from 4.3.3, the CDF for the fit voltage would be 0.500 which is within your 0.27&0.75 criteria, meaning use the Gaussian fit rather than interpolation?   

--- End quote ---
First compute the 0.25 and 0.75 percentile from the CDF using the interpolation method (i.e. the first and third quartiles in voltage). In this case, this would be at 0.474V and 0.477V. The check is to verify that the voltage obtained from the Gaussian error function lies within these two bounds.

--- End quote ---

 :-DD  This is why I ask.  Something so simple, left to my own, I will get it wrong.    I have gone ahead and made this change and will try it out tonight. 

SJL-Instruments:

--- Quote from: joeqsmith on February 02, 2024, 10:10:44 pm ---Your initial comment was:

--- Quote ---This only matters at low triggers/sample or samples/cdf, when the data is very noisy and the fit might blow up.
--- End quote ---

You didn't define "low", but the manual states:

--- Quote ---When no trigger is present, the scope will trigger off its internal clock (100 Mtrig/s) until a valid trigger source returns.
--- End quote ---
and also:

--- Quote ---The main limitation of the CDF sampling technique is for signals with infrequent trigger opportunities (500 ktrig/second or lower).
--- End quote ---

By low, did you mean < 500ktrig/sec?  If so, internal trigger does not fall into that category? 

--- End quote ---
Here we meant that the fit may give noisy results when the setting for "triggers per sample" (i.e. Nmin and Nmax in the Advanced CDF Settings) is low. This is unrelated to the trigger rate. Apologies for any confusion.

joeqsmith:

--- Quote ---Apologies for any confusion.
--- End quote ---
No problem.  Always best to ask.   

Before writing code to sweep the DC, I decided to try shorting the inputs.  Interesting, without that last change it will create NaNs.  I assume expected.  With the check added,  it has been running for about 15 minutes now without a fault.   So it does appear to be required in some cases.   You may want to include that in the manual as well.

SJL-Instruments:

--- Quote from: joeqsmith on February 03, 2024, 12:15:01 am ---Before writing code to sweep the DC, I decided to try shorting the inputs.  Interesting, without that last change it will create NaNs.  I assume expected.  With the check added,  it has been running for about 15 minutes now without a fault.   So it does appear to be required in some cases.

--- End quote ---
Is this in your custom software, or our software? The check should not be required for shorted inputs - it's there only for low-sample situations where the data is very noisy. May be worth tracing down where the NaNs are coming from.

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