Author Topic: x1 Oscilloscope Probe Shootout  (Read 6106 times)

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Offline EEVblogTopic starter

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x1 Oscilloscope Probe Shootout
« on: September 20, 2023, 12:09:31 pm »
The Rigol PVP3150 vs the Siglent PP510 oscilloscope probes in x1 mode.
Choose your fighter.

 
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Offline TomKatt

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Re: x1 Oscilloscope Probe Shootout
« Reply #1 on: September 20, 2023, 12:26:52 pm »
1X probes don't get the love they should get...  For many tasks that don't require 10's of Mhz - such as audio, many power supplies, serial ports and even many small ucontroller testing a 1X probe can offer better resolution than a 10X probe.

My Probe Master 4901-2 1X/10X has a 1X BW of 10Mhz (love these!).  The fixed 1X 4903-2 has a BW of 30Mhz (the shorter 1m cable 4903-1 goes to 38MHz).  Even the DIY coax 1X clip probes I made go 20Mhz+ 

Seems like fixed 1X probes perform better than switchable versions.

But extremely interesting video - I was not aware the Rigol PVP3150 performs that well in 1X mode.  That's impressive.
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Offline EEVblogTopic starter

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Re: x1 Oscilloscope Probe Shootout
« Reply #2 on: September 20, 2023, 12:38:17 pm »
My Probe Master 4901-2 1X/10X has a 1X BW of 10Mhz (love these!).  The fixed 1X 4903-2 has a BW of 30Mhz (the shorter 1m cable 4903-1 goes to 38MHz).  Even the DIY coax 1X clip probes I made go 20Mhz+ 
Seems like fixed 1X probes perform better than switchable versions.

Nice!
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Offline gamalot

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Re: x1 Oscilloscope Probe Shootout
« Reply #3 on: September 20, 2023, 12:44:15 pm »
Rigol PVP2150/2350 also have 35MHz bandwidth in 1x mode.
« Last Edit: September 20, 2023, 12:46:45 pm by gamalot »
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Offline TomKatt

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Re: x1 Oscilloscope Probe Shootout
« Reply #4 on: September 20, 2023, 12:52:14 pm »
Rigol PVP2150/2350 also have 35MHz bandwidth in 1x mode.
Wow!  If those are real specs those probes rival much more expensive competitors.

I wonder what the engineering trick is for getting such high BW at 1X...  I'm guessing the cable capacitance plays a large part.  I've noticed that the coax used on my Probe Master's is a bit thicker and more robust (but even more supple silicone) compared to most oem probes provided - which is great for production floor or rough environments.

Edit - in any event, glad to see 1X demonstrated as being much more capable than generally considered.

Edit 2 - I see the Rigol datasheet has a footnote indicating the 35Mhz BW 'Connected to an appropriate Rigol Oscilloscope'.  I'm guessing the scope front end capacitance is also a factor affecting BW.

« Last Edit: September 20, 2023, 01:12:17 pm by TomKatt »
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Online mawyatt

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Re: x1 Oscilloscope Probe Shootout
« Reply #5 on: September 20, 2023, 01:13:20 pm »
Interesting Dave, what were the relative input capacitances on the two test probes? Wonder if they are using inductive peaking in the Rigol to extend the BW in 1X mode?

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Offline gamalot

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Re: x1 Oscilloscope Probe Shootout
« Reply #6 on: September 20, 2023, 01:20:27 pm »
Rigol PVP2150/2350 also have 35MHz bandwidth in 1x mode.
Wow!  If those are real specs those probes rival much more expensive competitors.

I wonder what the engineering trick is for getting such high BW at 1X...  I'm guessing the cable capacitance plays a large part.  I've noticed that the coax used on my Probe Master's is a bit thicker and more robust (but even more supple silicone) compared to most oem probes provided - which is great for production floor or rough environments.

Edit - in any event, glad to see 1X demonstrated as being much more capable than generally considered.

Edit 2 - I see the Rigol datasheet has a footnote indicating the 35Mhz BW 'Connected to an appropriate Rigol Oscilloscope'.  I'm guessing the scope front end capacitance is also a factor affecting BW.

The retail price of PVP2150 in China is 185 yuan (equivalent to about 25 US dollars), and its selling point is the bandwidth in 1x mode.

Many sellers are selling the PVP2150/2350 separately, and no one mentioned that it needs to be used with a Rigol's scope to achieve the claimed bandwidth, so I guess it should work with other brands.
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Offline TomKatt

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Re: x1 Oscilloscope Probe Shootout
« Reply #7 on: September 20, 2023, 01:29:57 pm »
Many sellers are selling the PVP2150/2350 separately, and no one mentioned that it needs to be used with a Rigol's scope to achieve the claimed bandwidth, so I guess it should work with other brands.
I'm sure that it does.  Although I don't believe I've ever encountered an issue using different probes, I have read that certain probes can sometimes not play well with equipment it wasn't designed for because of impedance mismatches.  But I suspect most of the scopes in this range have similar enough parameters that these probes would work fine.
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Offline TomKatt

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Re: x1 Oscilloscope Probe Shootout
« Reply #8 on: September 20, 2023, 02:24:13 pm »
So I definitely should have watched Dave's video explaining 1X probes and why their BW is frequently so much lower than the 10X switched setting, where he explains that the probe cable is not regular coax but rather a specialized resistance wire designed as a lossy transmission line to help improve the higher BW on the 10X setting.  This also explains why my home-made 1X probe with generic coax performs so much better than a typical 1X/10X probe.

Which begs the question - are better 1X BW probes like these Rigol examples mentioned here using conventional coax cable, with other engineering design elements negating the need for the resistive lossy wire used in more conventional 1X/10X probes?  Perhaps materials and cable technology have evolved since Tek developed the lossy cable design so many years ago?  It seems like their 1X 30Mhz+ BW is very similar to straight coax.  But if this can be done, I wonder why high BW 1X/10X probes are so rare?

 
« Last Edit: September 20, 2023, 03:26:36 pm by TomKatt »
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Offline mwb1100

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Re: x1 Oscilloscope Probe Shootout
« Reply #9 on: September 20, 2023, 04:14:28 pm »
Edit 2 - I see the Rigol datasheet has a footnote indicating the 35Mhz BW 'Connected to an appropriate Rigol Oscilloscope'.  I'm guessing the scope front end capacitance is also a factor affecting BW.

I think the footnote applies to both bandwidth specs (x1 and x10).  The footnote indicator is coincident with the Chinese text for "Bandwidth" and they simply didn't bother also putting it on the English translation.

My guess is that they say the specs apply only when used with Rigol scopes because that they don't want to be bothered with complaints from or supporting people using them with other scopes or with people complaining that they don't get 350MHz bandwidth when they plug their PVP2350's to a DS1054Z (I'm certain this happens more often than you might guess).
 

Offline artur0089

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Re: x1 Oscilloscope Probe Shootout
« Reply #10 on: September 23, 2023, 02:58:34 pm »
There is a mistake somewhere in the video!!!
There is no increase in frequency response!

DS2302A & DG1062Z, sine wave, sweep 0,1-30 MHz, Linear.
« Last Edit: September 23, 2023, 10:13:18 pm by artur0089 »
 

Offline alm

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Re: x1 Oscilloscope Probe Shootout
« Reply #11 on: September 23, 2023, 05:41:26 pm »
So I definitely should have watched Dave's video explaining 1X probes and why their BW is frequently so much lower than the 10X switched setting, where he explains that the probe cable is not regular coax but rather a specialized resistance wire designed as a lossy transmission line to help improve the higher BW on the 10X setting.  This also explains why my home-made 1X probe with generic coax performs so much better than a typical 1X/10X probe.
What makes you think reflections from the impedance mismatch at the scope and circuit ends are not a problem for 1x probes? I know Dave was a bit misleading in this video, but see page 14 and further of Tektronix Probe Circuit Concepts (1969), despite the age the most thorough thorough published resource on oscilloscope probes.

It may well be that the optimal resistance of the coax is different for 1x and 10x, but I sincerely doubt a plain 50 Ohm coax of any decent length will give good performance with a high impedance circuit. Try simulating it in something like LTspice with a fast pulse. I just measured a dedicated 1x probe (Tek P6101B), and the resistance was about 260 Ohm for the 2m version.

I don't like switchable attenuation probes just because the switch will always switch to the other setting at the worst moment and you'll spend a while messing around until you figure out it was the stupid switch, and then go out and buy dedicated 10x and 1x probes. The bandwidth of 1x probes are rarely an issue for me. If I need bandwidth, I'll use other solutions like low-Z probes (source permitting), extra amplification, active (differential) probes or other solutions. 1x probes are just the easiest / cheapest solution.

Offline artur0089

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Re: x1 Oscilloscope Probe Shootout
« Reply #12 on: September 23, 2023, 09:59:54 pm »
Try simulating it in something like LTspice with a fast pulse.
;)
Real devices are more interesting...
Rigol PVP3150 / X10 - yellow.
Coax 50 Ohm + attenuator 50 Ohm 6 db / X15 - grey.
Delta rise/fall - +500 ps.
« Last Edit: September 24, 2023, 11:59:58 am by artur0089 »
 

Offline alm

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Re: x1 Oscilloscope Probe Shootout
« Reply #13 on: September 24, 2023, 08:39:28 am »
Real devices are more interesting...
Rigol PVP3150 / X10 - yellow.
Coax 50 Ohm + attenuator 50 Ohm / X1 - grey.
Delta rise/fall - +500 ps.
Assuming that 50 Ohm attenuator is a terminator (otherwise it's not x1), then of course it will perform well for a low impedance source. But it's irrelevant to this topic, which is about x1 high impedance probes, which are a different beast. Try using this probe on a high impedance (~kOhm) source, or with a higher voltage source, and see how it performs. The latter might burn out the terminator.

Offline artur0089

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Re: x1 Oscilloscope Probe Shootout
« Reply #14 on: September 24, 2023, 11:39:25 am »
otherwise it's not x1
You are right, 6 dB reduces the amplitude by half, i.e. "X5".
I provided this screenshot to show the REAL operation of the equipment, and not its simulation in software.
Each probe behaves individually on a square wave.
Rigol PVP3150 is very good! FFT won't let me lie.
The signal after Rigol PVP2350 is more distorted.
with a higher voltage source
The level on the generator is the same on both measurements
« Last Edit: September 24, 2023, 12:05:26 pm by artur0089 »
 

Online Kleinstein

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Re: x1 Oscilloscope Probe Shootout
« Reply #15 on: September 24, 2023, 11:53:10 am »
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.
 

Offline rf-loop

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Re: x1 Oscilloscope Probe Shootout
« Reply #16 on: September 24, 2023, 05:55:55 pm »
The Rigol PVP3150 vs the Siglent PP510 oscilloscope probes in x1 mode.
Choose your fighter.



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:
« Last Edit: September 25, 2023, 05:56:11 am by rf-loop »
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Offline MathWizard

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Re: x1 Oscilloscope Probe Shootout
« Reply #17 on: September 24, 2023, 11:02:32 pm »
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.
« Last Edit: September 24, 2023, 11:04:47 pm by MathWizard »
 

Offline artur0089

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Re: x1 Oscilloscope Probe Shootout
« Reply #18 on: September 25, 2023, 03:18:53 am »
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!..
« Last Edit: September 25, 2023, 09:06:39 am by artur0089 »
 
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Offline gf

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Re: x1 Oscilloscope Probe Shootout
« Reply #19 on: September 25, 2023, 07:19:32 am »
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.

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.

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.

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.

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.
« Last Edit: September 25, 2023, 08:21:15 am by gf »
 

Online 2N3055

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Re: x1 Oscilloscope Probe Shootout
« Reply #20 on: September 25, 2023, 08:28:19 am »
Best way would be to go with coax from AWG output to a T that is connected directly on BNC on reference channel set to 50Ω. Then connect a probe to that T.
That creates 25Ω feed point directly on reference input channel.
That is optimal way for Bode and also for waveform comparisons...

It is not important what is on output of AWG but what the reference scope channel sees..
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Offline artur0089

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Re: x1 Oscilloscope Probe Shootout
« Reply #21 on: September 25, 2023, 08:49:48 am »
Best way
use of two generator channels.
The input capacitance of X1 probes is 50-120 pF.
Without interference and distortion, T-split operates up to 2 MHz.
« Last Edit: September 26, 2023, 01:31:10 am by artur0089 »
 

Offline artur0089

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Re: x1 Oscilloscope Probe Shootout
« Reply #22 on: September 25, 2023, 09:20:25 am »
to go with coax from AWG output to a T that is connected directly on BNC on reference channel set to 50Ω. Then connect a probe to that T.
:-//
« Last Edit: September 25, 2023, 09:28:11 am by artur0089 »
 

Online 2N3055

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Re: x1 Oscilloscope Probe Shootout
« Reply #23 on: September 25, 2023, 09:21:38 am »
Best way
use of two generator channels.
The input capacitance of X1 probes is 50-90 pF.
Without interference and distortion, T-split operates up to 2 MHz.

Bode plot works by comparing against reference chanel. It is differential measurement...
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Online 2N3055

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Re: x1 Oscilloscope Probe Shootout
« Reply #24 on: September 25, 2023, 09:47:20 am »
Output of AWG is connected to T in CH1. CH1 is set for 50Ω. in other side of T you connect probe and connect probe's BNC to CH3.

In Bode plot you setup CH1 as reference channel and CH3 as output.

Whatever distortion in amplitude and phase happens at T compared to output of AWG is irrelevant.
Bode plot measures phase between CH1 and CH3, not relative to AWG...
« Last Edit: September 25, 2023, 09:49:03 am by 2N3055 »
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