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DSO4254C - Center frequency on FFT

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Post time 2019-7-2 02:34:31 | Show all posts |Read mode
Hi

SW 1.1.2(190326.0)
HW 501.001.001.000.000.000.000.000
FPGA a005

Currently in FFT center frequency is set to half of maximum span (after press VO knob)


But when i change span to 6.25 kHz and press VO knob center frequency is still set to half of maximum available span. It is realy anoying to rotate very long to achive 3.12 kHz (I start from 31.25 kHz and step is 0.01 kHz).


Is it possible to reach this faster?
Can it be implemented in new SW version that center frequency will be set after press VO knob according to current settings of span?

Example:
Span 62.50 kHz -> Center 31.25 kHz
Span 31.25 kHz -> Center 15.62 kHz
Span 12.50 kHz -> Center  6.25 kHz
Span   6.25 kHz -> Center  3.12 kHz

Of course only after VO knob is pressed.

Thanks



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Post time 2019-7-9 14:37:56 | Show all posts
Sir, you can put the test points on the center frequency point at a large bandwidth, and then zoom in to see the surrounding signal.

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 Author| Post time 2019-7-10 03:57:29 | Show all posts
Edited by TMG at 2019-7-10 04:28

Hi Amy
Yes I can zoom it but it isn't usable.1.
Here is standard view of sinus 6 kHz signal. Cursor show more or less correct value of frequency.


Here is zoomed view. Cursor show incorrect value.


Here is also zoomed view but shifted to the right.


Cursor show value according to scale on chart but not real frequency on FFT.
Frequency axis is not change when i shift left or right. The pick is on 6 kHz but on chart you can assume that is on 57 kHz (this is not true value).
2.
Or maybe you talking about that method
I set span to 3.12 kHz and center frequency to 6 kHz and get this

Then i change span to 1.25 kHz but center frequency is changed to 250 Hz (strange)

Then i change span to 625 Hz and center frequency back to 6 kHz.

After another span change to 6.25 kHz center frequency is set to 250 Hz (again not good)

Every second change of span center frequency is OK and for rest is NOK. Is this should work in that way or i miss something?
Thanks for your answer.









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Post time 2019-7-15 16:52:43 | Show all posts
I have feedback to the engineer. He will modify it later.

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Post time 2019-7-16 09:43:26 | Show all posts
FFT function is unavailable in double window mode.

Please use the firmware to update.




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 Author| Post time 2019-7-17 05:20:40 | Show all posts
Hi Amy

For this Firmaware 1.1.2 (190715.0) Center frequency is constant when i change span - this is OK.

But is not possible to lower center frequency below half of maximum span.

Example:
My maximum span is 625.00 kHz - center frequency for this is 312.50 kHz (after press VO knob) - OK.
When i rotate VO knob CW then center frequency change immediately to 625.00 kHz (maximum span) this is NOK
When i rotate VO knob CCW then center frequency is increased as expected - OK
When i have center frequency set higher than half of maximum span e.g. 350 kHz and rotate VO knob CW then center frequency is decreased till i reach half of maximum span (in my case 312.50 kHz) then jump to 625.00 kHz

It is also not possible decrease center frequency below 312.50 kHz when i change span to 312.50, 125.00, 62.50 kHz.

I'm looking forward for next firmware update.


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Post time 2019-7-26 16:46:45 | Show all posts
Sorry to reply you so late.
We will update the firmware in next week, please wait for a while.

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Post time 2019-8-2 15:15:14 | Show all posts
Please use this to update.



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 Author| Post time 2019-8-7 00:24:34 | Show all posts
Hi Amy

In SW dso4kb_20190802.upk problem was solved Thank you!
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