Products > Test Equipment
x1 Oscilloscope Probe Shootout
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Kleinstein:
The performance of a x1 probe may depend on the input impedance of the scope. The can make a difference in the response and if one sees a slight peaking or not. Also the signal source impedane can make a difference.

I would expect the switchable x1 / x 10 probes to be some compromise and fixed probes may be a bit better. On the low price end it looks like that one mainly gets the switchable ones.
rf-loop:

--- Quote from: EEVblog on September 20, 2023, 12:09:31 pm ---The Rigol PVP3150 vs the Siglent PP510 oscilloscope probes in x1 mode.
Choose your fighter.



--- End quote ---

Nice video...but...but... absolutely essential informations are missing, so evaluating whether the received data is bullshit or whether it even has any value other than entertainment.

Or is this some kind of "engineer joke".

How you have connected signals (exactly) and how you have setup BodePlot. Is it displaying/measuring Vin/Vout or Vout.. (I do not know how these settings are in R&S

Think example possible VSWR effect. If Bode measure Probe in and then compare it to Ref In (after this coaxial (mismatch to 1M input) and after this other mismatch done with  T split to probe input.
It has also been completely forgotten that according to normal practice Probes are classified by measuring the 25ohm source impedance.

So nearly all possible mistakes have been made carefully.

Look your generator output where is connected Probe input using T  for split it to Probe and then to coaxial what goes to Bode Reference.
Now if Bode is on Vin/Vout mode signal in probe input is totally other than signal in reference input point... except when signal is very low freq or DC.

Also  @artur0089 test may give some reason for thinking...

This is bit alarming in this video. Is this really engineer made test setup what is partially visible here:
MathWizard:
I've only ever owned or used 1 AWG, my SDG2142X. So sometimes when I'm looking at distortions on my scopes, IDK if it comes from the AGW, the probes, or the scopes. Sometimes at higher frequencies I'm sure it's the probes, and reflections. But it makes me wonder what the AWG really outputs sometimes.

But looking at the prices of them, for now I should just get more suitable probes and coax accessories.
artur0089:
Problem found! The signal swing in the reference cable is reduced.
DS2302A & DG1062Z, sine wave, sweep 0,1-30 MHz, Linear.
Coaxil - blue.
Rigol PVP3150 - yellow.
===================
T-split - evil!..
gf:

--- Quote from: rf-loop on September 24, 2023, 05:55:55 pm ---Think example possible VSWR effect. If Bode measure Probe in and then compare it to Ref In (after this coaxial (mismatch to 1M input) and after this other mismatch done with  T split to probe input.
It has also been completely forgotten that according to normal practice Probes are classified by measuring the 25ohm source impedance.

So nearly all possible mistakes have been made carefully.

Look your generator output where is connected Probe input using T  for split it to Probe and then to coaxial what goes to Bode Reference.
Now if Bode is on Vin/Vout mode signal in probe input is totally other than signal in reference input point... except when signal is very low freq or DC.

--- End quote ---

If the probe tip is attached to one leg of the T, and the other leg goes via coax to the (50 Ohm) reference input, then the reference input "sees" the same voltage as the probe tip (delayed by the cable length). Ideally, there won't be significant reflections from the scope back to the T (unless the 50 Ohm input is crap). The voltage at the T is of course not the same as the generator voltage, nevertheless Vin/Vref is the probe's frequency response. But indeed, the source impedance cancels out and the frequency response is measured as if source impedance were zero, i.e. the loading of the circuit by the probe is not considered.

In order to measure the frequency response including a 25 Ohm source resistance, I think the following configuration should work:
Feed the generator output into the input of a 2-resistor power splitter. Connect one output leg of the power splitter to the (50 Ohm) reference input and attach a T to the other output leg of the power splitter. Attach the probe tip to the 2nd leg of the T and terminate the 3rd leg of the T with 50 Ohm. Then the voltage at the probe tip is suposed to be VRef*Zin/(Zin+25), where Zin is the input impedance of the probe, i.e. a 25 Ohm source resistance is included in the measured frequency response.


--- Quote from: EEVblog on September 24, 2023, 11:54:08 pm ---
--- Quote from: rf-loop on September 24, 2023, 05:55:55 pm ---Look your generator output where is connected Probe input using T  for split it to Probe and then to coaxial what goes to Bode Reference.
Now if Bode is on Vin/Vout mode signal in probe input is totally other than signal in reference input point... except when signal is very low freq or DC.

--- End quote ---

I think you are right, I needed to use a x10 high bandwidth probe here. I'll re-run it and see what I get.

EDIT: I quickly re-ran it and there was little difference.

--- End quote ---

I don't see how a high-Z probe for the reference measurement would make a significant difference (it rather introduces additional unceretainty, due to its own frequency response). Regardless how you measure the voltage at the probe tip and use it as Vref, you measure the probe's frequency response as if source impedance were zero.
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