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Siglent SSA3000X Plus math trace unexpected res
g00se:
I’m trying to understand how the Math trace function is supposed to work in spectrum analyzer mode on the SSA3000X Plus.
To test, I enable a math trace of Power Diff, X-Y+0, where the X and Y traces are exactly the same (Clear Sweep, Max Peak). I expect to see the math output trace to just be a flat trace at 0dB, but instead I see a flat third trace that looks to be about -95dB offset.
If I try to “capture” an ambient trace and switch it to View, and subtract this from a second Clear Sweep trace of the same general source, I expect to see minimal peaks from 0dB representing the differences, but instead I see a messy trace that jumps up and down all the way from -95dB to the Clear Sweep trace value…
If I try a simple offset value for my math function, like 10dB offset of one trace, it displays as expected.
The manual is not much help, and I can’t find any videos of the Siglent math trace in action. There are some videos of the Rigol DSA doing a math trace, and it looks to behave how I would expect.
Has anyone here used the Siglent math trace function to subtract two traces successfully?
Performa01:
I don't think this is something SSA-specific, it's just fundamentals.
0 dB = 1 = 100%
whereas
0 = -infinity dB.
If the result of a math operation is zero, then you should get the maximum negative value for a dB result, which seems to be about -95 dB in this case.
rf-loop:
--- Quote from: g00se on January 08, 2023, 04:21:39 am ---I’m trying to understand how the Math trace function is supposed to work in spectrum analyzer mode on the SSA3000X Plus.
To test, I enable a math trace of Power Diff, X-Y+0, where the X and Y traces are exactly the same (Clear Sweep, Max Peak). I expect to see the math output trace to just be a flat trace at 0dB, but instead I see a flat third trace that looks to be about -95dB offset.
If I try to “capture” an ambient trace and switch it to View, and subtract this from a second Clear Sweep trace of the same general source, I expect to see minimal peaks from 0dB representing the differences, but instead I see a messy trace that jumps up and down all the way from -95dB to the Clear Sweep trace value…
If I try a simple offset value for my math function, like 10dB offset of one trace, it displays as expected.
The manual is not much help, and I can’t find any videos of the Siglent math trace in action. There are some videos of the Rigol DSA doing a math trace, and it looks to behave how I would expect.
Has anyone here used the Siglent math trace function to subtract two traces successfully?
--- End quote ---
Are you measuring dB values with Spectrum analyzer? Least I do not know how much is just one dB. Sorry but I have not seen any SA what measures dB. Or are you perhaps measuring example dBm levels as we usually measure with rf-spectrum analyzers.
How much is 10dB or 0dB or what ever dB. My answer is "nothing".
How much is 10dBm or 0dBm. 0dBm is 1mW and 10dBm is 10mW and then how much is 100 dBm. No it is not 100 mW. It is 1e10 mW aka 10000000000mW (10 MW yes Mega Watt)
Now I ask you, how much is a dBm - a dBm (you told you have two equal traces). Is it 0dBm :-DD
Or how much is 0dBm - 0dBm. Is it 0dBm. No it is not. It is 0mW. How many dBm it is?
You tell there read -95dB perhaps you mean -95dBm (95dB below 0dBm)
0dBm is 1mW power
-95dBm is 0.000000000316 mW ! 0.316 pW.
g00se:
Yes, sorry the units are dBuV. I was hoping to “subtract” the ambient signals from my scan of device under test for EMC pre-compliance.
I was hoping to do something similar to what is shown here using a Rigol analyzer:
g00se:
I captured some screens to try and illustrate:
Here is just an ambient sweep:
Here is ambient + device sweep:
and this is what the math trace looks like, trying to subtract the first trace from the second:
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