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HP 54520A does it support XY mode?

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neazoi

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HP 54520A. Does it support XY mode? Please help
 

albbg

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They usually have a math function to do this. In your case it could be the "versus" function.
 
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In your case it could be the "versus" function

Right, unlike modern DSOs that have X-Y mode selectable under horizontal settings, 54520A has it under math functions.
 
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neazoi

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Right, unlike modern DSOs that have X-Y mode selectable under horizontal settings, 54520A has it under math functions.

Yes, that is right, it is the VER (versus) function. In the same menu, it also has FFT function, it can be converted into a spectrum analyzer up to it's limit of 500MHz. Resolution is about 1.3KHz.
I have tested the FFT and although quite slow at it's full resolution (because of the FFT calculation) it is useable. I am so excited!
I hope it is quite reliable in dbm measurements. If I remember well, by testing the same signal on the scope function the Vpp is not exactly as it should be expected (it is greater) based on this table. http://www.neazoi.gr/conv.pdf Could it be a calculation error or miscalibration?

An analogue scope that I owned gave more Vpp amplitude on the same signal generator I tested, but I was testing it on 1Mohm. Right now I am testing it on 50 Ohm on the 54520A, giving a lower amplitude signal, so I hope it is more accurate.
 
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albbg

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Your table is correct and the conversion between volt and dBm is valid only for a 50 ohm terminated system. The measurement with the scope in high impedance you should have the voltage doubled with respect to the scope terminated on the same impedance of that of the generator. If your generator is 50 ohm impedance and you see 1 Vpp with the scope terminated onto 1 Mohm then you will see 50 ohm/(1Mohm+50 ohm)*1Vpp≈0.5 Vpp.

Could you post the values you have read: Vpp on the scope and dBm from FFT ?
 
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neazoi

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Your table is correct and the conversion between volt and dBm is valid only for a 50 ohm terminated system. The measurement with the scope in high impedance you should have the voltage doubled with respect to the scope terminated on the same impedance of that of the generator. If your generator is 50 ohm impedance and you see 1 Vpp with the scope terminated onto 1 Mohm then you will see 50 ohm/(1Mohm+50 ohm)*1Vpp≈0.5 Vpp.

Could you post the values you have read: Vpp on the scope and dBm from FFT ?

The fft measures 4.5-5dbm and I should expect a maximum of 1.125vpp, but when switching to scope I get a little bit more at 1.4vpp.
Is that normal?
 

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No, 3 dB difference seems to me too much. In case of miscalibration I would expect a difference between generator setting and scope measurement, but good agreement between trace and FFT.
Could you say what about the frequency of your signal, the RBW of the FFT, the horizontal set of the scope (total acquisition time and sampling time) and the windowing type (flat top, Blackmann Harris, etc.)
 

neazoi

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No, 3 dB difference seems to me too much. In case of miscalibration I would expect a difference between generator setting and scope measurement, but good agreement between trace and FFT.
Could you say what about the frequency of your signal, the RBW of the FFT, the horizontal set of the scope (total acquisition time and sampling time) and the windowing type (flat top, Blackmann Harris, etc.)

Hello,
Sorry it took me so long to respond.
I did some tests and here are the results.

1. In scope mode:
1.61vpp

2. In FFT mode:
FFT1 (Hamming - frequency resolve) 7.5dbm
FFT2 (Rectangular - transitions) 5.8dbm
FFT3 (Flat top - amplitude acc.) 8.5dbm

Any thoughts?
 

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