Author Topic: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank  (Read 20686 times)

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Offline Electro Fan

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While not quite as challenging to answer as “which came first the chicken or the egg?”, “do I need 4 channels or can I live with 2 channels on a scope” seems almost as difficult to answer for some of EEVbloggers – especially those contemplating a Rigol DS1000Z vs a RS2000 series scope.

So in an effort to derive wisdom from the many wise users here, here is the question and a chance t learn from others who share their experience:

A.   I have a 2 channel scope and I’ve never had a need for 4 channels.

B.   I have a 2 channel scope and I seldom have a need for 4 channels but when I do the reason I need 4 channels the most is to __________________.

C.   I have a 2 channel scope and I often have a need for 4 channels and when I do the reason I need 4 channels the most is to __________________.

D.   I have 4 channel scope and I often use 4 channels especially for __________________.

E.   I have a 4 channel scope and generally only need 2 channels but when I need 4 channels it’s mostly for __________________.

F.   I have a 4 channel scope but I never use more than 2 channels.

Please copy and paste your vote (and any blank filling-in) into a new "reply".  Feel free to add other comments but please include the letter on the front end to make the responses easy to scan.  Thx

Thanks to anyone and everyone who can chime in.  EF
« Last Edit: September 28, 2013, 04:22:40 pm by Electro Fan »
 

Offline Wytnucls

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #1 on: September 28, 2013, 09:48:09 pm »
If you don't know if you need a four-channel scope, you don't need one.
 

Offline jancumps

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #2 on: September 28, 2013, 09:49:22 pm »
E....It's mostly for the obvious: seeing relation between 4 related signals.
 

Offline Electro Fan

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #3 on: September 29, 2013, 01:32:44 am »
Ok, I can see that so far this hasn't been the most inspirational question.

I get the idea that 4 channels would be most useful in seeing the relationships between 4 signals and that if you don't know what 4 signals you would be interested in seeing you don't need 4 channels.  That's all pretty insightful and helpful.  (Not really.)

Maybe everyone who has a two channel scope has concluded that they are just fine with two channels, if that's true, let's hear it.  If someone started out with 2 channels and discovered it was a limitation, that would be interesting to understand also.  Likewise if everyone with a 4 channel scope uses 3 or 4 channels vs. 1 or 2 on a regular basis, what are the signals and relationships you are looking at that require more than 2 channels?
 

Offline grego

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #4 on: September 29, 2013, 03:05:13 am »
The price delta from a 2 to 4 channel scope (on models that support either) is usually so insignificant you may as well just get the 4.
 

Offline echen1024

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #5 on: September 29, 2013, 03:20:38 am »
C or D. I like to monitor many test points at once, and lack a logic analyzer, so SPI signals are a pain in the ass for me.
I'm not saying we should kill all stupid people. I'm just saying that we should remove all product safety labels and let natural selection do its work.

https://www.youtube.com/user/echen1024
 

Offline kg4arn

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #6 on: September 29, 2013, 03:23:59 am »
I often use 3 channels.  It is handy to use the full capability of one input channel to trigger from and I often use 2 of the remaining channels to probe.  The external trigger input can be used but on my DSO you cannot see the external trigger signal, so I mainly use that if the signal generator is driving the circuit.
 

Offline Electro Fan

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #7 on: September 29, 2013, 04:04:22 am »
The price delta from a 2 to 4 channel scope (on models that support either) is usually so insignificant you may as well just get the 4.

This is true on the DS4000 series, but when comparing the DS1000 and DS2000 series it's not so straight forward.  The DS2072 provides a better/bigger screen and better overall performance than the DS1000; the DS1000 has the 4 channels - but to get from either the 1000 or the 2000 to the 4000 is about a 3x uplift.  So, if you want to stay at $1k or less and stay with Rigol you have to decide how likely the 4 channel usage will be.

So far we have SPI and trigger on one channel while probing two other channels as valid reasons for a 4 channel scope.  I'm sure there are other reasons to go with 4 channels - hope we can hear some more from forum members.
 

Offline vk6zgo

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #8 on: September 29, 2013, 06:00:53 am »
E. I have a 4 channel scope and generally only need 2 channels,but when I need 4 channels it’s mostly for redundancy ( when one of the plugin channels "croaks", I still have two spares on the other plugin). ;D
 

Offline Smokey

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #9 on: September 29, 2013, 06:15:41 am »
Always had minimum of 4 channels, always will.
Example: motor drives.  Especially for 3phase drives I wish I had 9+ channels sometimes.  Bare minimum is 4 and you are still having to disconnect something you really want to watch to make that work.  Assuming PWM drives, High and low side drives and phase-current on all 3 phases = 9 signals that would be really nice to watch all at once.  Sometimes you can get away with just digital (logic analyzer) type measurements but sometimes you really want to watch for miller effects and such so you need the analog channels.  That's just normal operation.  That's not even getting into the protection circuitry timing and correlating that with current levels and control signals.

For a lot of stuff you really only need 2 channels (or 1 even), but when it comes up that you need 4 and you don't have them you are hosed.  The cool thing is that you don't often need full bandwidth on all 4 channels but still want to scope a lot of signals, which is why I started the Rigol DS1000Z AND DS2000 topic when it was pointed out the price difference between that combo and a DS4000. 
https://www.eevblog.com/forum/testgear/buying-both-rigol-ds1000z-and-ds2000-scopes/
That really only becomes relivant once you made the decision that you need AT LEAST 4 channels though.
 

Offline cosmos

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #10 on: September 29, 2013, 06:43:36 am »

I always had 4 channels at work and at home.
I have a Lecroy 7200 (very noisy, big, slow, and hot), and a french Metrix USB/Ethernet MTX1054 (too slow update rate (10Mb Ethernet) and I do not like the SW)
When I need more than 2 it is typically for debugging digital signals so an MSO 2+8 or 2+16 would seem to do what I need.
Hantek MSO5102D proved to be useless at sampling the digital signals as they only provide 4k sample memory and advertise 512k, and SW is full of bugs.
Now I try Rigol DS4014 and that looks really good. Only thing I have against it so far is that the fan is a bit noisy, but that can be fixed 
 

Offline peter.mitchell

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #11 on: September 29, 2013, 09:58:04 am »
D.   I have 4 channel scope and I often use 4 channels especially for being a lazy git and doing short term datalogging.
 

Offline KedasProbe

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #12 on: September 29, 2013, 10:06:43 am »
I have 10 channels, ok, 8 are digital but still 10.
Not everything that counts can be measured. Not everything that can be measured counts.
[W. Bruce Cameron]
 

Offline kv3x

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #13 on: September 29, 2013, 06:02:48 pm »
A  --  Ok, I'll vote for the lowly two channel scope. 

I have a 465B and the recent acquisition of a DS2072.  These fit well with my requirements...  Maybe I don't know enough to know what I'm missing...

 

Offline jpb

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #14 on: September 29, 2013, 06:34:22 pm »
I've not yet used my 4 channel scope enough to give a sensible answer. I went for 4 channels on the grounds that if I found I only used 2 it would be slightly annoying but I could live with it, whilst if I got a 2 channel scope and found I needed 4 channels I'd have to buy another scope!

My general thought was that 4 channels can give you both V and I (via a resistor) on both the input and output of a circuit or in general if characterizing a circuit it is likely that two measurements on both input and output will give a more complete picture than just one magnitude for each.

One thing for digital 4 channel scopes is that even when using 2 channels by using channel 1 and 3 you get the full sample rate and memory.
 

Offline fpga

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #15 on: September 29, 2013, 07:11:53 pm »
It all depends on what you are planning to use it for.

Most of the analog scopes were only 2 channel, and these were perfectly sufficient for both design and repair of most of the analog TVs and radios of the era.

I think that for most purely analog design work 2 channels should be sufficient. For repair work, where you only need to check the presence and 'quality' of a waveform, 2 channels should be sufficient.

Things begin to change if you are designing mixed signal, control, data acquisition, or micro interfaces where you frequently need to monitor the relationship between more than 2 channels. Digital channels on a MSO or a logic analyzer are great for digital debugging, but they tell you almost nothing about the shape of the waveform, and can't measure skew, slew rates, etc.

Even a simple measurement like the power supply ramp-up and reset needs a 4 channel scope, because ramp-up is a concern if there are generally two or more power rails.

For mixed signal and micro controller work, the question to ask would be:

A 4 channel DSO or a 2 channel MSO with 8 or 16 digital channels?

In my case, I'm fortunate enough to have the Agilent MSOX3024A which is a great pleasure to use. Only thing I wish is that I had at least one channel with higher bandwidth such that I could view the integrity of my clock and other critical signals, but the need for that would be occasional, where everything else is frequently used.
I never did a day's work in my life, it was all fun -- Thomas Edison.
 

Offline jancumps

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #16 on: September 29, 2013, 07:18:59 pm »
To be honest, I think I use 4 channels because I've got them. Before I had a 4 channel scope I only used 2 channel scopes. I'm not doing anything different now, maybe a bit more efficient and user friendly.

(confession: when I bought my scope - 2nd hand - I didn't know it had digital option and 4 channels. The 2 additional channels are hidden on the back. I just bought it because of the price and because I was used to work with that brand)
 

Offline grego

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #17 on: September 29, 2013, 07:32:48 pm »
The price delta from a 2 to 4 channel scope (on models that support either) is usually so insignificant you may as well just get the 4.

This is true on the DS4000 series, but when comparing the DS1000 and DS2000 series it's not so straight forward.  The DS2072 provides a better/bigger screen and better overall performance than the DS1000; the DS1000 has the 4 channels - but to get from either the 1000 or the 2000 to the 4000 is about a 3x uplift.  So, if you want to stay at $1k or less and stay with Rigol you have to decide how likely the 4 channel usage will be.

So far we have SPI and trigger on one channel while probing two other channels as valid reasons for a 4 channel scope.  I'm sure there are other reasons to go with 4 channels - hope we can hear some more from forum members.

Which is why I said "on models that support either".  You're talking about model line changes and there are dramatic differences there in price, performance and features.  It's an apples/oranges comparison.

The price delta on models that support either (be it Tektronix, Agilent, Rigol, etc) is pretty minimal between 2 and 4 - you should get 4.

You're adding more restrictions now throwing a price cap into the mix.  If you have a budget of $1000 you need to determine what will drive your purchasing decision.  Do you need serial decodes?  Do you need wfm/s?  What kind of bandwidth?

If it's just a question of "2 or 4" the answer should pretty much always be "4" especially when you can get 4 for under $500 more than 2 in pretty much all cases.  Under $300 in some cases.
 

Offline Electro Fan

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #18 on: September 29, 2013, 08:14:11 pm »
The price delta from a 2 to 4 channel scope (on models that support either) is usually so insignificant you may as well just get the 4.

This is true on the DS4000 series, but when comparing the DS1000 and DS2000 series it's not so straight forward.  The DS2072 provides a better/bigger screen and better overall performance than the DS1000; the DS1000 has the 4 channels - but to get from either the 1000 or the 2000 to the 4000 is about a 3x uplift.  So, if you want to stay at $1k or less and stay with Rigol you have to decide how likely the 4 channel usage will be.

So far we have SPI and trigger on one channel while probing two other channels as valid reasons for a 4 channel scope.  I'm sure there are other reasons to go with 4 channels - hope we can hear some more from forum members.

Which is why I said "on models that support either".  You're talking about model line changes and there are dramatic differences there in price, performance and features.  It's an apples/oranges comparison.

The price delta on models that support either (be it Tektronix, Agilent, Rigol, etc) is pretty minimal between 2 and 4 - you should get 4.

You're adding more restrictions now throwing a price cap into the mix.  If you have a budget of $1000 you need to determine what will drive your purchasing decision.  Do you need serial decodes?  Do you need wfm/s?  What kind of bandwidth?

If it's just a question of "2 or 4" the answer should pretty much always be "4" especially when you can get 4 for under $500 more than 2 in pretty much all cases.  Under $300 in some cases.

On the front end I tried to mention that the question was driven in part by the Rigol 2000 vs 1000Z trade-off.  Without a doubt on higher end scopes the uplift isn't that much % wise for 4 channels.

I know you are looking at a Rigol MSO4000 which will probably be an excellent scope.  The MSO4000 seems to have nicely split Agilent down the middle with pricing comparable to the Agilent 2000 series and functionality that competes perhaps more closely with the Agilent 3000 series.  If $ were no concern I'd love an Agilent MSOX3000 or even a DSOX3000 which could be upgraded toa MSOX.  Or a Rigol MSO4000 would be cool and even a Rigol DS4000 would be great (but unfortunately it appears no way to get to a MSO from there).  With any of these I'd go for 4 channels.  No one can argue that 4 channels is bad.

So it's really just a trade-off in this case driven by a desire to keep the budget closer to $1k than $2k.  Serial decodes are a definite - especially I2C; maybe RS232; SPI users consistently say 2 channels doesn't cut it.  I just can't tell if giving up waveform performance, memory, screen size, and other features, functions, and performance in return for 4 channels is a sensible tradeoff.  If I knew what I was likely to want a year or two down the road it would be easier to make the choice.  Some guys buy a scope knowing everything they ever intend to do with a scope - that isn't me; I'm planning to learn and grown into the scope.  So I appreciate any insight.  At the end of the day it's just a piece of grear but I'm enjoying the studying/learning process. 

Thx again for any insights on what specifically anyone is doing with a scope that drives them to want/need 4 channels.
 

Offline Electro Fan

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #19 on: September 29, 2013, 08:18:16 pm »
Greg, Just out of curiosity, given your experience with various scopes and your desire to move to a MSO with a small ton of channels - if for some reason you had to live either a Rigol DS2000 (and only 2 channels) or a Rigol DS1000Z (4 channels but less performance, features, functions, etc.) - which would you take?  Thanks, EF
 

Offline grego

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #20 on: September 29, 2013, 08:40:20 pm »
Greg, Just out of curiosity, given your experience with various scopes and your desire to move to a MSO with a small ton of channels - if for some reason you had to live either a Rigol DS2000 (and only 2 channels) or a Rigol DS1000Z (4 channels but less performance, features, functions, etc.) - which would you take?  Thanks, EF

I would probably go for the 1000Z if only because of the channels.  I do a bunch of stuff with CAN so regardless with either of those I'd have an external LA for decodes.  There's not so many differences between the 1000Z and 2000 (not 2000-S mind you) that I couldn't live quite happily with the 1000Z.  It really just depends on your needs.

If you're looking sub $2000 a viable option could be the Instek GDS2000A series.  I know I returned mine but that was because of mis-stated specifications.  If you can live within what it offers you have the ability to add decodes with just a module and get 4 channels.  It's not a bad scope, it just didn't suit my needs once the specifications got correctly translated from Chinese.

In my case I could live with a lower end scope and a separate logic analyzer but I'm trying to conserve bench space - so a MSO with decode options is a good choice for me.  Plus, while I work with CAN, I don't need a zillion digital channels like some of the LAs offer so 8 or 16 works.  That's just me though.  Am I overbuying?  From a scope perspective, yes, but MSO functionality is important to me in what I work with so it is what it is.
 

Offline tonybarry

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #21 on: September 29, 2013, 11:12:36 pm »
Hi ElectroFan,

In response to your survey ...

-----
D.   I have 4 channel scope and I often use 4 channels especially for related signal timing issues.
-----

I often have four digital signals and one or two analog signals (yeah - that does add up to more than 4.  Hmmm.)  so I spall off the analog and the most important digital signals to the scope and then use a PC based LA to grab what I need in the digital domain.  Marrying the timebases up is currently a bit tedious because triggering is frequently based on a digital point rather than an analog point.  That may all change with the next scope ...

Regards,
Tony Barry
 

Offline Electro Fan

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #22 on: September 29, 2013, 11:46:27 pm »
Hi ElectroFan,

In response to your survey ...

-----
D.   I have 4 channel scope and I often use 4 channels especially for related signal timing issues.
-----

I often have four digital signals and one or two analog signals (yeah - that does add up to more than 4.  Hmmm.)  so I spall off the analog and the most important digital signals to the scope and then use a PC based LA to grab what I need in the digital domain.  Marrying the timebases up is currently a bit tedious because triggering is frequently based on a digital point rather than an analog point.  That may all change with the next scope ...

Regards,
Tony Barry

Hi Tony,

Thanks - any chance you could say more about the types of digital signals you typically work with and also about what analog and/or digital signals you would ideally most like to marry/synchronize on the time bases (and how precisely you need to synchonize them)?  Are you measuring the level of synchronicity with numeric readouts or eyeballing (or triggering) where rising and falling signals line up?  What next scope(s) are you considering?  Thx, EF
 

Offline Electro Fan

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #23 on: September 29, 2013, 11:49:55 pm »
A  --  Ok, I'll vote for the lowly two channel scope. 

I have a 465B and the recent acquisition of a DS2072.  These fit well with my requirements...  Maybe I don't know enough to know what I'm missing...

kv3X - Thanks.  What are the capabilties on the 2072 that you most enjoy vs. what you have with the 465B?  EF
 

Offline Electro Fan

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Re: 2 vs 4 Channel Oscilloscope Poll - multiple choice plus fill-in the blank
« Reply #24 on: September 29, 2013, 11:53:09 pm »
It all depends on what you are planning to use it for.

Most of the analog scopes were only 2 channel, and these were perfectly sufficient for both design and repair of most of the analog TVs and radios of the era.

I think that for most purely analog design work 2 channels should be sufficient. For repair work, where you only need to check the presence and 'quality' of a waveform, 2 channels should be sufficient.

Things begin to change if you are designing mixed signal, control, data acquisition, or micro interfaces where you frequently need to monitor the relationship between more than 2 channels. Digital channels on a MSO or a logic analyzer are great for digital debugging, but they tell you almost nothing about the shape of the waveform, and can't measure skew, slew rates, etc.

Even a simple measurement like the power supply ramp-up and reset needs a 4 channel scope, because ramp-up is a concern if there are generally two or more power rails.

For mixed signal and micro controller work, the question to ask would be:

A 4 channel DSO or a 2 channel MSO with 8 or 16 digital channels?

In my case, I'm fortunate enough to have the Agilent MSOX3024A which is a great pleasure to use. Only thing I wish is that I had at least one channel with higher bandwidth such that I could view the integrity of my clock and other critical signals, but the need for that would be occasional, where everything else is frequently used.

In my book a MSOX3024A would be the Cat's Meow  :-+
Enjoy!
 


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