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So I have spent the past two days going through various budget oscilloscopes and checking their specs VS price. Most of the information I have gathered has been from here and I am almost sold on an MSO-19. The only reason I haven't bought it already is that it's a single channel oscilloscope and before I spend £180 on it, I want to make sure it's going to cover 95% of my electronics needs. I think my major problem is that I don't know what area of electronics I will be going into in the future and so can't predict exactly what I am going to need.

Currently I work as a software engineer and so am already playing around with PICs, AVRs and MSP430s. I think, in the short term, I will be looking into making small intelligent robots (not bump and turn stuff you see on most hobbyist sites but something with 'character'). I have been in AI for a number of years and whilst I'm no Marvin Minsky, I do know a thing or two about what makes something seem intelligent.

The other thing I have been looking at is this 32-channel logic analyser (Open Workbench Logic Sniffer) which is only £30 and is a more powerful logic analyser than comes with the MSO-19. Would it be a better idea just to buy that?

I'm open to other suggestions too but I don't want to spend over £250 in total if I can help it.

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Thanks for the great answers. I bought the DSO-2090 as suggested in the accepted answer. –  Mr. Hedgehog Oct 23 '10 at 21:44
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9 Answers 9

up vote 7 down vote accepted

I agree with the others that two-channels is very convenient at times. Particularly if there is a separate trigger input (almost like a third channel).

What are your minimum bandwidth requirements? Do you really need something as fast as the MSO-19? The DSO-2090 is a 100MS/s, 40 MHz dual channel (plus external trigger) PC-based scope for £139. You would then have money left over to buy the standalone £30 logic analyzer.

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Good suggestion! Thanks. –  Mr. Hedgehog Oct 22 '10 at 18:07
    
Did not even think of pointing out bandwidth, I forget how often people do not realize how little bandwidth they need. –  Kortuk Oct 22 '10 at 18:52
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@Nat, unless you are doing very high-speed digital, or RF work, you should be able to get by with 40 MHz. That is typically about the highest clock rate of most microcontrollers, and most signals (SPI, I2C etc) will be much slower than that. For looking at audio or PWM signals (for robotics), you don't need much at all. In any case, make sure you get a good set of probes, which might run another £20 or more. –  tcrosley Oct 22 '10 at 20:11
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Think of wanting your bandwidth to be 3-10 times faster than your highest speed signal. it never hurts to have too much bandwidth, but it can really hurt to have too little. –  Kortuk Oct 22 '10 at 21:49
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@Nat, as I pointed out in my earlier comment, you generally won't be looking at any signals near the internal clock speed of the microcontroller. SPI clocks generally run at a few MHz, and I2C clocks are usually only 400 KHz. A fast UART is 115K baud. A typical PWM frequency for motor control might be 40 KHz -- a 40 MHz scope would allow you to see very narrow PWM pulses. –  tcrosley Oct 23 '10 at 15:40
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A single channel scope is a complete waste of time. Maybe worth a fifth of a 2-channel one. You almost always want to look at the relationship between signals.

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As soon as you get a single-channel, you will want the double-channel. Heck, I have a double and am shopping for a four-channel. You will get to the stage where you need to compare signals, for education, troubleshooting or fun. With your budget of 250 quid you should be able to scrape in with the perennial favourite, the Rigol DS-1052E.

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Looks like it can be modded to 100MHz - very cool: eevblog.com/2010/03/31/… –  Mr. Hedgehog Oct 22 '10 at 14:36
    
Yes, I forgot about that... :| –  tronixstuff Oct 22 '10 at 14:54
    
I'll wait for some more opinions but the Rigol looks good (even if it does stretch the budget). Also, I can only find non-UK sources to buy it at £250 meaning I'm probably gonna be hit with an import charge. Any comments on the logic sniffer? –  Mr. Hedgehog Oct 22 '10 at 15:17
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You need two channels for most tasks.

The reason that two channels is import is you often interested in the relationship between different signals. Here are some examples of when two channels can be very important:

  • A clock signal and a data signal where you need to check the setup and hold timing.
  • An enable signal to an analogue circuit, where you need to see how fast the analogue circuit stabilises after being enabled. This might be the case in a low power system where an sensor is only powered up when it needs to be sampled.
  • To examine the relative timing of some tasks on a microcontroller, where you set each task to toggle a different IO pin upon entry and exit.
  • Where you have a PWM output with a complementary drive and you need to confirm the dead time between the top and bottom switches.
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On trick which can occasionally be useful for eking out an "extra" channel with digital signals is to use a resistor to combine to signals and then examine the resulting trace. Depending upon what the signals are, such a resulting signal may be easier or harder to read than the two original signals (usually harder to read, but sometimes things work out nicely). –  supercat Dec 6 '11 at 15:52
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It's worth scouring eBay for a second hand DSO.

I got my Tektronix TDS-210 for £180:

  • 2 channel + separate trigger
  • 60MHz
  • 1 GS/s

I bought an Open Logic Sniffer too. It's a great device for the price, but given the tiny amount of RAM it has, it feels a bit like keyhole surgery.

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Single-channel scopes should be banned! Most of the times you want to see (at least) two signals in relation to each other. Two examples:

Phase
Phase for a single signal is meaningless, you always compare phase with the phase of another signal. You can do this by looking/estimating how much time the signal has shifted, but the better way is to look at the Lissajous figure in XY-mode. Single-channel scopes don't have XY-mode.

Serial protocols
Except for Manchester coding data and clock are separate on most protocols. Want to analyze your data with only the data channel? Like this:

enter image description here

Well, good luck! This is the SDA channel of an I2C bus. Any idea of what it represents? Not without the clock:

enter image description here

Now you not only can see what SDA is on each clock pulse, you can also see the I2C start condition: SDA going low while the clock is high. Impossible on a single-channel scope.

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If you are only going to deal with low speed digital signals then a logic sniffer will get the job done.

If you get higher speed you may need an o-scope to check for signal integrity issues.

If you do analog, you are going to want an analog o-scope.

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It is virtually impossible to use a single channel oscilloscope other than for basic measurements.

Dual channel allows you to debug most serial protocols. It is also crucial for the analysis of complex signals, like video (for example, with my OSD project I need to compare the video signal and Csync.)

Heck, I have a quad channel scope and I say if you can get one second hand for a little extra I say it's well worth it.

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I have the MSO-19 and I like it. It works well under VMWare on my Mac. I do often find myself wanting a 2nd channel, however.

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