Products > Test Equipment

Pocket-Sized 6 GHz 1 TS/s ET Scope

<< < (46/107) > >>

joeqsmith:
To get some idea how the gain changes with temperature, again, looking at channel 2.   Here is the start of the previous dataset, again the first test right after reworking the board with it cold.   I repeated this test about 3 hours later with the scope running other tests that entire time.  Notice, the gain did not change at all.   

It's possible that things were not stable prior to reworking the board.  That couple of hours I mentioned working on it wasn't an embellishment.   I would guess I touched 20 joints conservatively but most likely more in the order of 50. 

joeqsmith:
Showing channels 1-4 at the start of run 6.  Again, this is after reworking the board and with it having been running for 3 hours.    We can clearly see there is a gain error but notice the spread of the positive apex is tighter than at the negative apex.  The scope has always behaved this way but that spread has opened up with the increase in gain.   I can't tell from looking at the manual if these are considered normal.   

SJL-Instruments:

--- Quote from: joeqsmith on February 02, 2024, 03:26:57 pm ---Looking at post 197 showing all 4 channels prior to rework.  You can see, they were never really matched well.  After rework, they have spread apart even further.   I would need to run some tests to determine how much is due to gain vs offset but it sounds like it currently isn't  possible to correct for them anyway.  Are there plans to add some sort of alignment procedure to your software that could be saved?

--- End quote ---
The next revision of the software has a one-click tool for trimming the DC offset.
This will of course not fix any gain error. You can try testing the DC linearity with the internal trigger to see if there's an overall scaling error. Global scaling error should be around 1%, with a linearity of around 0.1%.
The frequency-dependence of the gain error cannot in general be fixed for a sampling scope.


--- Quote from: joeqsmith on February 02, 2024, 03:26:57 pm ---When you specify the maximum DC RMS (section 1.5), are you running internal trigger with all inputs shorted?   

--- End quote ---
The specification applies to measuring any stable signal and analyzing the resulting RMS deviations from the mean.
Running internal trigger with inputs shorted is a special case of this.


--- Quote from: joeqsmith on February 02, 2024, 05:03:35 pm ---Again, looking at channel 2.  Showing the first set of data after I reworked the board.  We are looking at sweeps on the X-axis, hourish of time.  This is subtracting the mean from the signal as previously described.  Note how the noise level decreases as it warms up.

--- End quote ---
This is known behavior - after warmup, the RMS noise should be somewhat better than the specification.


--- Quote from: joeqsmith on February 02, 2024, 05:22:20 pm ---Showing channels 1-4 at the start of run 6.  Again, this is after reworking the board and with it having been running for 3 hours.    We can clearly see there is a gain error but notice the spread of the positive apex is tighter than at the negative apex.  The scope has always behaved this way but that spread has opened up with the increase in gain.   I can't tell from looking at the manual if these are considered normal.   

--- End quote ---
The spread occurs primarily in the 11-11.5 ns region and should be unrelated to signal level. It should be lower after 12 ns.
This is known behavior and limits the minimum ENOB specification at 1 GHz.

joeqsmith:

--- Quote ---This is known behavior - after warmup, the RMS noise should be somewhat better than the specification.
--- End quote ---


--- Quote ---The spread occurs primarily in the 11-11.5 ns region and should be unrelated to signal level. It should be lower after 12 ns.
This is known behavior and limits the minimum ENOB specification at 1 GHz.

--- End quote ---


Thank you very much for supplying those valuable tips!! 


--- Quote ---You can try testing the DC linearity with the internal trigger to see if there's an overall scaling error. Global scaling error should be around 1%, with a linearity of around 0.1%. 
--- End quote ---

Before working with the internal trigger, I would want to implement your other correction as I assume the internal trigger is considered low.


--- Quote ---We also have a check that the extracted fit voltage lies between the 25th and 75th percentile of the CDF. If not, we revert to using the interpolation method. This only matters at low triggers/sample or samples/cdf, when the data is very noisy and the fit might blow up.

If you keep Nmax above 500 and K above 20, this shouldn't be an issue.

--- End quote ---


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. 

Verdict it still out on if these glitches will show up after rework.  The plan is to run the hardware up until the software is ready, or until I get bored watching it... Which ever comes first.  :-DD

joeqsmith:

--- Quote ---We also have a check that the extracted fit voltage lies between the 25th and 75th percentile of the CDF. If not, we revert to using the interpolation method.

--- End quote ---

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?   

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod