Author Topic: What is the "best" Oscilliscope that I can get for $30,000?  (Read 20172 times)

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Offline bdunham7

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Re: What is the "best" Oscilliscope that I can get for $30,000?
« Reply #150 on: November 13, 2021, 06:22:21 pm »
There is a good reason that the capture should not overflow the sides of the display, it slows down the acquisition rate and increases blind time. Ideally it should be user controlled, which the zoom mode of just about every single scope does.

Acquisition rate and blind time are usually not so critical that a 4-screen capture would be a problem.  I just happen to have found that to be handy at times.  However, as I've said before, it is more of a scope operation and screen management issue than an actual obstacle to doing some work.  I would forgive Siglent entirely if they would just allow me to shrink the whole record display to a small bar at the top like you'd see on my Tek, instead of using half the screen.  You should see the SDS1104X-E with zoom and FFT and measurements at the same time!  The response was some joke about curtains.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline BILLPOD

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Re: What is the "best" Oscilliscope that I can get for $30,000?
« Reply #151 on: November 13, 2021, 08:53:42 pm »
Good Morning Symax,   Save your lunch money and get one of these: https://hackaday.com/2018/09/24/tearing-into-a-1-3-million-oscilloscope/ :-BROKE
 

Offline kcbrown

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Re: What is the "best" Oscilliscope that I can get for $30,000?
« Reply #152 on: November 13, 2021, 10:25:37 pm »
There is a good reason that the capture should not overflow the sides of the display, it slows down the acquisition rate and increases blind time. Ideally it should be user controlled, which the zoom mode of just about every single scope does.

Acquisition rate and blind time are usually not so critical that a 4-screen capture would be a problem.  I just happen to have found that to be handy at times. 

None of these systems limit the maximum capture time.  That is strictly a question of setting the timebase.

But they do limit the minimum capture time.  The single-screen Siglent approach allows for a much smaller (compared to what you describe, by a factor of 4) minimum capture time than does a multi-screen approach.  However, note that the Instek, at least, has carefully matched the minimum capture length (1000 points) with the minimum timebase, such that a single capture of that length fills only the screen, and thus allows no zooming out.  You have to set a larger capture length for that.

How much of a difference does that really make?  Likely, not much in the grand scheme.  But that obviously depends on the nature of the capture requirements.  Blind time could easily dominate the total interval between trigger events such that the acquisition length makes no real difference until the timebase is much larger than the minimum.  But Siglent's dedicated sequence capture mode essentially eliminates the blind time (or so I'm led to believe), leaving only the capture length itself.  But you have to go out of your way to use that mode.


Quote
However, as I've said before, it is more of a scope operation and screen management issue than an actual obstacle to doing some work.  I would forgive Siglent entirely if they would just allow me to shrink the whole record display to a small bar at the top like you'd see on my Tek, instead of using half the screen.  You should see the SDS1104X-E with zoom and FFT and measurements at the same time!  The response was some joke about curtains.

I completely agree.  Siglent needs to implement the option to make zoom mode look like the normal display on, for instance, the Instek, so that you have a little indicator at the top of the screen showing the position and size of the zoom window within the capture itself.

For the 2000X+ series and the other scopes with a larger screen, this is much less of an issue, and the amount of screen real estate used for the zoomed portion of the waveform display is quite ample.   I wouldn't mind having the same option described above for that scope as well, but the screen size and resolution makes it quite usable.  As scope screens get bigger and increase in resolution, this issue will essentially disappear.
« Last Edit: November 13, 2021, 10:41:50 pm by kcbrown »
 

Offline EEVblog

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Re: What is the "best" Oscilliscope that I can get for $30,000?
« Reply #153 on: November 14, 2021, 05:06:16 am »
I've come to the conclusion that I should probably get a fully decked out SDS5104X (1 GHz, 4 CH).  Totally decked out I saw the cost is $11,308.00.  If there are options I should unselect that I could "hack" I'd be interested in hearing about it.

Why do you need 1GHz?  :-//
You are vastly better off getting a 350MHz or even 500MHz model and a whole bunch of useful probes like HV diff probes, current probes and active probes.
Anything above about 500MHz is pretty useless with your normal passive probes anyway.
If you really need GHz range then get an older used scope in the several GHz range just for that task.


Do you believe that example Tektronix TPP1000 passive 1GHz probes are just useless and made for joking. Perhaps you think Tek do not know what they design and do.  No they are serious with also this product. But naturally also it need some real knowledge how to use and for what. As is with most serious T&M instruments and tools mostly, even nowdays.

It's got 4pF input capacitance. At 1GHz that's 39ohms. Enjoy.

Siglent don't even make or supply a matching 1GHz passive probe for that 1GHz scope do they?
This is why Siglent sell a 1GHz active probe with 1.2pF input cap.
 

Offline tautech

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Re: What is the "best" Oscilliscope that I can get for $30,000?
« Reply #154 on: November 14, 2021, 05:49:18 am »
Siglent don't even make or supply a matching 1GHz passive probe for that 1GHz scope do they?
This is why Siglent sell a 1GHz active probe with 1.2pF input cap.
What else would fit their SAPBus interface ?
SAP1000 and new models SAP2500 and SAP2500D differential probes.
https://siglentna.com/products/accessories/probes/active-probes/

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Offline rf-loop

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Re: What is the "best" Oscilliscope that I can get for $30,000?
« Reply #155 on: November 14, 2021, 10:47:46 am »
I've come to the conclusion that I should probably get a fully decked out SDS5104X (1 GHz, 4 CH).  Totally decked out I saw the cost is $11,308.00.  If there are options I should unselect that I could "hack" I'd be interested in hearing about it.

Why do you need 1GHz?  :-//
You are vastly better off getting a 350MHz or even 500MHz model and a whole bunch of useful probes like HV diff probes, current probes and active probes.
Anything above about 500MHz is pretty useless with your normal passive probes anyway.
If you really need GHz range then get an older used scope in the several GHz range just for that task.


Do you believe that example Tektronix TPP1000 passive 1GHz probes are just useless and made for joking. Perhaps you think Tek do not know what they design and do.  No they are serious with also this product. But naturally also it need some real knowledge how to use and for what. As is with most serious T&M instruments and tools mostly, even nowdays.

It's got 4pF input capacitance. At 1GHz that's 39ohms. Enjoy.




Even when it is not specified but can you tell where in this circuit is this capacitance. Yes I know it do not exist in any special position in circuit.
But also I know, and hope also you understand, there is also other things, whole complex circuit instead of one 4pF capasitance if you look how 1GHz or 10GHz see it.
There is three elements. R, C and L.  Yes there is also L.  Take example probe tip. Now just only for thinking purpose, not real from just this probe.
Think if there is 8mm 0.7mm wire, example just probe tip (if go more deep even it is itself complex circuit). Alone 8mm 0.7mm piece of wire is roughly 5nH inductance (also with parasitic series and parallel C). But this imagined tip simple series XL is around 31ohm. Now there is then this C what is example 4pF in this case. It is not one C in one place. It is least partially "parasitic" capacitance "here and there"  but then we have also other pole what we call "GND" and  also there signal travel through L  and together with parasitic capasitances there, everywhere, every single piece of wire is complex (R)LC.  Try draw this whole circuit with all lumped parasitics... and then how it interact with also complex circuit of DUT... what is then whole circuit when probe is connected. How this whole circuit behave.  :o
Also it is good to think where this GHz signal travel. DC travel well inside whole wire...

Word is bit more complex than 4pF 39pF @1GHz, think about it.

What I try tell. It is MUCH more complex thing than one kids schoolbook ideal 4pF capacitor and its XC.

It also mean that probing high frequency circuit is very complex and end of day state of art and need carefully think how probing change/affect DUT circuit.

How complex it is... more deep we go, more complex it is.

It need also note that least an passive probes freq bandwidth  and risetime is defined in accordance with general practice for an test signal source impedance of 25 ohms.


« Last Edit: November 14, 2021, 10:55:02 am by rf-loop »
I drive a LEC (low el. consumption) BEV car. Smoke exhaust pipes - go to museum. In Finland quite all electric power is made using nuclear, wind, solar and water.

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Offline Electro Fan

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Re: What is the "best" Oscilliscope that I can get for $30,000?
« Reply #156 on: November 14, 2021, 03:40:53 pm »

How complex it is... more deep we go, more complex it is.


Maybe why this is known as rf-loop?  :) :-+, :) :-+, … :) :-+,
 
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Offline bdunham7

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Re: What is the "best" Oscilliscope that I can get for $30,000?
« Reply #157 on: November 14, 2021, 04:52:17 pm »
What I try tell. It is MUCH more complex thing than one kids schoolbook ideal 4pF capacitor and its XC.

It also mean that probing high frequency circuit is very complex and end of day state of art and need carefully think how probing change/affect DUT circuit.

How complex it is... more deep we go, more complex it is.

It need also note that least an passive probes freq bandwidth  and risetime is defined in accordance with general practice for an test signal source impedance of 25 ohms.

A high-impedance high-frequency passive probe is always a challenge and I do have to wonder what the use case is.  As for your 'complexities', on the older 500MHz 8pf P6139A Tek actually published the relevant data in the manual.  I don't see that data for the TPP1000 but I suspect that the result will be similar--very low input impedance at the top of the range.  Other than really needing a (very expensive) single probe that 'does it all' and uses a 1M scope input, I don't see why I'd want that in my toolbox.  If the TPP1000 does have better (more) input impedance performance than basic math would indicate, they ought to tell us about it.

I have the P6139A and also a P6156 10X 1pF that has a relatively constant 500R input out to several GHz.  It obviously needs a 50R input, but it has a clear advantage over even the high-performance P6139A above 100MHz.  They make 20X and 100X tips for the P6156, but I haven't scrounged them up yet--but the 100X apparently gives you a 5K input impedance up beyond 1GHz.  So IMO, high-impedance passive probes are an increasingly questionable choice as you go above 200MHz or so.  Yes, they nominally work with a 25R source impedance, but how helpful is that when you are working on a 390MHz garage door opener?


A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 
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Offline EEVblog

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Re: What is the "best" Oscilliscope that I can get for $30,000?
« Reply #158 on: November 17, 2021, 03:51:11 am »
What I try tell. It is MUCH more complex thing than one kids schoolbook ideal 4pF capacitor and its XC.
It also mean that probing high frequency circuit is very complex and end of day state of art and need carefully think how probing change/affect DUT circuit.
How complex it is... more deep we go, more complex it is.

This is why I said it's pretty useless once you get above 500MHz.
This is why almost all passive probe makers stop at 500MHz
Or as dunham7 said, even questionable once you get above 200MHz.

This is why buying a >500MHz scope, or even say 300MHz scope for general lab use and probing is generally just a waste.
If are "messing with RF sometimes" as the OP is, then save the money on the general lab scope and get a good spectrum analyser.
In bang-per-buck, a 300MHz class scope is better value than a 500MHz class, which is better value again than a GHz class scope.


 
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