Oscilloscopes, how many channels do you need?

[vk6zgo]

As another poster stated, 2+16 on an MSO isn't a bad option, I'd rather have that or even 2+8 than 4+0 in most circumstances. The exception is when I'm doing switch mode power supplies when even 4 analogue channels can seem limiting.

But it depends to a large extent what you do, if you don't do much digital then the digital channels will be largely superfluous.

One further thing: remember that most 2 ch scopes have a trigger input too, which in some instances can be a reasonable compromise. A one channel scope without an external trigger offers little more than a 2.5 digit DVM for practical purposes.

Edit: meant to say, two channels can do anything a four channel can do, just not at the same time. You just need to work a little harder. Remember that 4ch scopes have only become commonplace on the average bench in the past fifteen years or so.

"One further thing: remember that most 2 ch scopes have a trigger input too, which in some instances can be a reasonable compromise. A one channel scope without an external trigger offers little more than a 2.5 digit DVM for practical purposes."

I've never encountered a single channel Osciiloscope without an external trigger,even the cruddiest 10MHz analogs have them.--------not sure about the little "toy" pocket DSOs,though!

That was almost what I was referring to. I have a Velleman HPS10 LCD scope from many years ago, single channel 10MHz, no trigger, almost useless. I think I ever used it other than to switch it on to see if it worked, I couldn't find a reason to use it. There are others, the UT-81B for example.

On your other point,I've fixed equipment faults using a single channel BWD 'scope with a faulty trigger circuit,which were impossible to get a handle on using a DVM/DMM.

A DMM will be sufficient for many jobs,but some really do need a 'scope.
In those cases,any 'scope,is better than none.

I did say "A one channel scope without an external trigger offers little more than a 2.5 digit DVM for practical purposes", so I didn't completely discount it, but I still think it'd most likely end up in a drawer gathering dust unlike a DVM or certainly a DMM. :-)

I think we agree in general, I was just trying to dissuade anyone from even considering a single channel scope without an external trigger on it.

Out of interest,I Googled for  Velleman HPS10,& found the linked pix.

http://www.vellemanusa.com/images/products/0/hps10_f3.jpg

Ohh! The horror!
I then had a look at a few Youtube reviews,& things didn't get much better!

I also saw one for the UT-81B,
At least,Uni-T had a pretty good shot at the DMM part,but  the 'scope bit was still quite dismal.

On the other hand,although this thing* looks like it was designed to be operated by "Cabbage Patch Dolls",it is a real,usable test instrument,after you get past BNC connectors that become unscrewed,& knobs that fall off.

*http://www.eham.net/data/classifieds/images/364574.jpg

The "10MHz" in the spec is the 3dB down point,but it will still display up to 27MHz or so--obviously without voltage accuracy------and it has an external trigger!

[HighVoltage]

Sometimes I use 4 scopes at the same time and all 4 channels on each scope

[BillyD]

Heh...

You _need_ one.
You want two.
Three would be nicer.
You'd really like to have four.
Four, plus an ext trigger, is just peachy.
Four, ext trig, and a bunch of digital channels is ... more than I can afford.

I use mine to make pretty squiggly colored lines, so that my housemate thinks I'm doing something productive with my time.  The more squiggly colored lines, the more important she thinks my work is.

Hah that's very true! The same applies if you're going to take some cool pics or video of your bench - and don't forget to switch on some power supplies and soldering stat to get a few glowing led displays in there...

Going back to the original question, I've recently been using all 4 channels for some digital projects. As someone else said, a logic analyzer would probably have sufficed but it's a pain in the ass to set it up whereas the scope is always at hand and also gives you a better idea as to the integrity of the signals.
I think for analog work, 1 or 2 channels would suffice a lot of the time.
And as someone else said, I couldn't go back to 2 channels after having 4.

[Rupunzell]

Really, really depends on what is being worked on.

Two channels is plenty for most analog stuff. Four or more is some times required with no options.

My own preference is to use a Tek 7000 with one dual trace plug in and another dual trace plug in with a Current probe and Differential probe.
This gives two single ended inputs, one current channel and one differential channel. If the specific measurement requires a different set up, it gets configured as required. Key here is knowing precisely what information-data is needed and how to achieve that goal with minimal measurement error and affect of circuit or system behavior.

More channels is not always better as each node probe-item of instrumentation added can and often does affect how the circuit is operating. Before adding more probes -item of instrumentation of any kind, fully understand the effects of each probe-instrumentation added. This applies for anything from a DVM-VOM to O'scope to SA to DSA to Generator or any other item of instrumentation.


Bernice

[rx8pilot]

Great point Bernice.  Loading the circuit and injecting noise can have you chasing your tail til the end of time.

I feel like I have spent more time learning how to measure circuits than I have spent learning to design them.

Sent from mobile device.... Keeping it short and mis-spelled

[joeqsmith]

Article for a 4:1 channel expander

http://www.eeweb.com/blog/extreme_circuits/four-channel-oscilloscope-adaptor1

[nbritton]

So to restate the question for my own purposes, would you rather have a Siglent SDS1304CFL (4 channel 300 MHz) for $1,339 or a Rigol DS2072A (2 channel 300 MHz) for $839? Are two more channels worth $500 to you, and the frustration of using a crappy siglent scope?

The DS1054Z doesn't have enough bandwidth for me, so I think the crux of the issue, at least for me, is whether 4 channels is worth an additional $1,461 to get the Rigol DS4014 at $2300. I think the answer to that is a resounding no, because you could buy one DS2072A + three DS1054Z for that price and you would get a combined total of 14 channels and still save $264 over the DS4014! I think the sweet spot for me is the Rigol MSO2072A with 2 analog and 16 digital channels.

[Stephan_T]

Article for a 4:1 channel expander

http://www.eeweb.com/blog/extreme_circuits/four-channel-oscilloscope-adaptor1

Wow, that's the betteriser of oscilloscopes:
Use four of them on a Rigol 1000Z and you get a total of 16 channels which is 800% of the Siglent   

Jokes aside, the premiss of most posts here is to regard the oscilloscope as an analytical tool, but you can also see it as a presentation/demonstration device. The didactic value of a 4 channel scope is much much higher than a 2 channel one.

Take for example Jery Ellsworth's video about

Magnetic Logic - Forgotten Technology
https://www.youtube.com/watch?v=p7SkE5pERtA&feature=youtu.be&t=14m50

If you know what goes on there, you may also be able to analyse all the phenomena using just two channels, but for a presentation and to teach (others or your self), four channels draw a much better picture and spare you a thousand words.
I think, that's one of the major reasons why Dave also prefers a 4 channel scope for many of his videos.

[Fungus]

The results are in, and: There's about a 2:1 preference for four channels here on EEVBLOG.

Make of it what you will.