EEVblog Electronics Community Forum

Electronics => Beginners => Topic started by: atetheprincess on November 14, 2017, 11:01:59 am

Title: Oscilloscope advice: DS1054Z vs Tektronix TDA460A
Post by: atetheprincess on November 14, 2017, 11:01:59 am
Hello!
    I've done a bunch of reading on here, but still am uncertain, so I'm hoping you folks can help me make the right choice.  I've come to a point where I think owning an oscilloscope would be beneficial to me, and am very excited to learn how to use a new tool, and everything that goes along with it.  I've been doing arcade board and monitor repairs (90's JAMMA stuff).  Basically I'm trying to choose between buying a brand new DS1054Z (which I'd unlock upon purchase), or purchasing a local used but well cared for Tektronix TDA460A for half the price.  Since I'm not too familiar with the tools yet at this point, I'm not sure how they stack up against one another and if the savings is worth it or not (think of all the other tools I could buy with the $200 saved, you know?).  Any and all advice is very welcome.

Thanks ahead of time, and I'm excited to dig into some of the guides and other things once I have whichever scope in hand :).
Title: Re: Oscilloscope advice: DS1054Z vs Tektronix TDA460A
Post by: xani on November 14, 2017, 05:28:38 pm
What you're gonna use it for ? That's the most important question (also did you mean TDS460A) ?

The biggest advantage of hacked Rigol would be variety of protocol decodes and much bigger memory, and much higher sample rate. Is that something that looks like it would be useful in your job/hobby? And what beside that you want to do with it ?

Ability to probe a bus and just directly decode what's on it is really handy but you can then just use saved $$ to buy cheap logic analyzer if you're working with slow enough buses. But *then* that means you have to have PC nearby and have to fiddle around if you want to see both digital and analog signal at same trigger point.

Rigol definitely gives you a lot more options, the question is if future possibilites which you might or might not need are worth $200 to you?
Title: Re: Oscilloscope advice: DS1054Z vs Tektronix TDA460A
Post by: David Hess on November 14, 2017, 07:39:59 pm
I would prefer the TDS460A (I assume it is a TDS and not a TDA) especially at half the price but either would serve you well.

Tektronix TDS460A:

- Much higher bandwidth which is probably unimportant in your application.
- Much higher equivalent time sampling rate of 50Gs/s.
- More reliable and accurate automatic measurements.
- Dual timebases and triggers make up for lower record length.
- Separate offset and position functions.

Rigol DS1054Z:

- Newer with warranty and likely more reliable over the long term.
- Lighter and more portable.
- Higher real time sample rate although it is variable with number of channels.
- Longer record length.
- More advanced triggers.
- Higher waveform acquisition rate for displaying glitches.
Title: Re: Oscilloscope advice: DS1054Z vs Tektronix TDA460A
Post by: capt bullshot on November 14, 2017, 11:47:11 pm
Don't know much about the Rigol, I tend to stay away from Chinesium ...

But,
I've got an old and crusty TDS420 (just a smaller BW model of the TDS460), and my advice would be: stay away from that beast, except you get it for free or very few $
It is known to suffer from capacitor plague, so maybe you'll have to replace a lot of small SMT electrolytic caps one day, or someone would have done that before.
It has a quite low single shot sampling rate (100Ms/s afair), for a 150MHz scope (the TDS420 model), one would expect at least 1Gs/s today. Doesn't matter too much if you want to display repetitive signals, it just slows down then.
Having 400MHz BW is nice, but IMO not necessary for what you intend to do.

Best thing would be to check them out both, to see the difference in UI concepts (I don't like the TDS420 style menus too much, I'd prefer TDS220 style - one knob per channel, not select channel and then use the same knob for each channel).
And, the TDS460 is large and heavy (though not a real boat anchor), the Rigol is small and lightweight. That's a plus for the Rigol.
Title: Re: Oscilloscope advice: DS1054Z vs Tektronix TDA460A
Post by: rstofer on November 15, 2017, 02:00:33 am
And when somebody says "equivalent time sampling" realize that it is a bogus sample rate that applies only to repetitive signals.  It turns out that digital logic signals are seldom repetitive.  We usually want to trigger on a specific event and capture what happens next.  The event may never repeat.

The one shot full bandwidth sampling of the DS1054Z would lead me in that direction.
Title: Re: Oscilloscope advice: DS1054Z vs Tektronix TDA460A
Post by: tggzzz on November 15, 2017, 02:19:55 am
And when somebody says "equivalent time sampling" realize that it is a bogus sample rate that applies only to repetitive signals.  It turns out that digital logic signals are seldom repetitive.  We usually want to trigger on a specific event and capture what happens next.  The event may never repeat.

The one shot full bandwidth sampling of the DS1054Z would lead me in that direction.

ETS does indeed presume repetitive signals but, as you know full well, it isn't bogus. It usually doesn't matter that a so-called "digital" signal isn't repetitive when you are using a scope.

The scope is used to verify that the analogue signal is well behaved and will be interpreted correctly by the receiver as a digital signal - i.e. ensuring signal integrity. For that eye diagrams are perfectly sufficient. Once signal integrity is seen to be correct, you can switch to debugging the digital signal in the digital domain.

OTOH, if you want to fling the word "bogus" around, I suggest you start with 1GS/s scopes where 50MHz signals have visibly reduced amplitudes - often only 70% of the actual value.

Given the choice between a 50MS/s+1GHz scope or a 1GS/s+50MHz scope, I wouldn't hesitate to get the 50MS/s scope and completely ignore the 1GS/s scope.
Title: Re: Oscilloscope advice: DS1054Z vs Tektronix TDA460A
Post by: xani on November 15, 2017, 04:39:50 pm

OTOH, if you want to fling the word "bogus" around, I suggest you start with 1GS/s scopes where 50MHz signals have visibly reduced amplitudes - often only 70% of the actual value.
It is 70% amplitude because that's what the spec is... 50Mhz at -3dB.. you know, EXACTLY what manufacturer specified ? There is nothing bogus here, you just need to pony up (or hack it...) for higher bandwidth option.

But it would be nice if manufacturers specified in advertisements exactly what the split is as it is usually 1GS/s shared between 2/4 channels. But I guess one should always look up datasheet before buying

Quote
Given the choice between a 50MS/s+1GHz scope or a 1GS/s+50MHz scope, I wouldn't hesitate to get the 50MS/s scope and completely ignore the 1GS/s scope.
Which is fine if you only do repetitive RF signals but OP specified what he does and it is not repetitive RF signals.

Title: Re: Oscilloscope advice: DS1054Z vs Tektronix TDA460A
Post by: james_s on November 16, 2017, 06:01:20 am
I'm a big fan of those older Tek TDS scopes, but I'd be hesitant to recommend one to a beginner or as an only scope. They're great instruments but they do have a few warts, particularly leaky SMT caps that can be a pain to deal with. The power supplies in the TDS400 series are a bit problematic too, I've got two dead ones.
Title: Re: Oscilloscope advice: DS1054Z vs Tektronix TDA460A
Post by: Simon on November 17, 2017, 12:13:00 am
Have we finished? I will remove the unnecessary bickering from the thread, DO NOT start it again!
Title: Re: Oscilloscope advice: DS1054Z vs Tektronix TDA460A
Post by: james_s on November 18, 2017, 06:33:45 am
What bickering? I don't see anything particularly out of line here, unless it's been removed already.
Title: Re: Oscilloscope advice: DS1054Z vs Tektronix TDA460A
Post by: Simon on November 18, 2017, 06:34:25 am
What bickering? I don't see anything particularly out of line here, unless it's been removed already.
It's been removed as I said.