Hello!

I own an old second hand 20 MHz analog scope. It works fine, but it starts to show strange behaviors. I'm already saving money for a new one. I need it to be a digital scope, as most of my work is digital, and would really appreciate to capture non-periodical signals. A logic analyzer is just not enough for many tasks.

I'm considering to get a Tektronik TDS1001B. 2 channels, 40 MHz BW and 500 Ms/s real time, with 2.5k samples per channel, and very light and small. Black and white screen. This would already be quite expensive for my budget.

Going for a 60 MHz scope will raise the cost quite a bit more. There's the Tektronik model 60 MHz and 1Gs/s, and also others like the Agilent DSO3062A, which is much heavier and lacks of USB connection, but has a nice feature of rejecting the waves that go out of a predefined area. Also one from Gw-instek
http://www.farnell.com/datasheets/85367.pdf
which is in the prize range of the agilent, but 4 channels 100 MHz.

Going lower than the 40 MHz Tek, there's one from BK-precision
http://www.farnell.com/datasheets/105325.pdf
25 MHz and only 250 Ms/s, but much cheaper.
And others which lack of FFT feature and thus I reject.

I find quite interesting this one
http://www.welec.de/english/06_suppo...ons_W2022A.htm
200 Mhz, 2 channel, 1Gs/s, colour LCD and cheaper than the Tek... it seems too good to be true.

My main concern is, will the 40 MHz Tektronik model will be enough for general electronics ? I'm a little unexperienced in scopes, but as a digital electronic, 40 MHz seems like very low for me, and also 500 Ms/s real time sampling is not great. Well, what I like the most about Tektronik is that it seems a good company, and offers life time warranty, while the others just one year.

If you ask me what I want it for, I'd say, I want it for everything :-)
Well, as much I can get from it, the better.

Originally Posted by patroclus

Hello!

I own an old second hand 20 MHz analog scope. It works fine, but it starts to show strange behaviors. I'm already saving money for a new one. I need it to be a digital scope, as most of my work is digital, and would really appreciate to capture non-periodical signals.

You realize analog or digital, the way the scope works internally doesn't dictate whether or not you can use it for digital or analog applications?

I guess in the end you have to weight whether or not the cost of paying all that extra money to be able to view a digital signal in analog is worth it, or whether a much cheaper, faster logic analyzer will do.

That BK one is really cheap. $500! The only thing it is missing for me is a logic analyzer. I might have to drop my ultrasonic project just to buy it.

How much is that W2000? I would also reject one without an FFT.

Well, to my understanding, analog requires lower bandwidth than digital, since to capture a 40MHz square wave properly you also need to capture it's harmonics (up to lat least 9th or 11th or something like that). While with a 40MHz RF thing, you only need to capture up to 40Mhz or maybe a few times that, but not up to the 11th.

THat W2000 is listed as being $1395 Euros...that's not exactly cheaper than the other scopes.

EDIT: After looking at them I would go with the Agilent DSO3062A. THat's the one I'm putting on my list. It costs just as much as the Tektronix 60MHz 1Gs but has a colour screen and seems more capable. BUt like you said, it's heavier, but I don't know what you mean by it having no USB, because it does.

WHy are the Tek scopes half the size of the Agilent scopes? THat is kind of strange. THe tek has a Go-NoGo function. THey are two small buttons on the top right- they just aren't as large or as fancy (multi-coloured backlit) as the Agilent ones.

Originally Posted by kep

hi all
so how about pc base oscilloscope having same capabilities isn't they cheap

I rules those out soley because it's so MUCH MUCH faster to have 10 fingers and two hands working the scope rather than a single mouse cursor.

The differences I can find are this:
-Running multiple channels reduces the sample rate of the Agilent Scope while the Tek ones claim to have the same sample rate regardless of the number of channels being run
-The Tek FFT has 2x as many sample points
-The Tek FFT has half the averaging resolution of the Agilent (Tek has 2, 4, 8, 16, 32, 64, 128 or 256 while the Agilent as 2, 4, 6, 8, 16, 32, 128, 256 or something like that)
-THe Agilent SEEMS to have a mode where it can acquire as soon as you push a button rather and completely ignoring the trigger altogether (unlike capturing a single trigger sequence by pusing a button.). It's a bit vague so I can't tell for sure.
-The Agilent has an adjustable variable BW digital filtering thing
-THe agilent can measure things like overshoot, duty cycle, and pulse width automatically.
-Both have a USB slave but only the Tek has a USB host (for flash drives).
-THe Agilent has a larger colour screen.

And though obviously biased, the Tektroniks videos comparing theirs and the Agilent scopes make some strong points if they are indeed true. I am leaning over to the Tektroniks. One thing is obvious, it's smaller! That bandwidth thing is a huge issue though, Tektroniks seems to say the Agilent scope only has a display of 500Ms, but if you check the scope curves carefull it shows the sampling rate is only half that (something about the Agilent scope being based off, if not a repackaged version of a scope from some company).

Have you tried checking out TekSelect at Tekstronics? You can get a TDS1002 (the 60MHz 1Gs scope) for $500 refurbished or a TDS1001B for the same price. Remember, that's a TDS1002, not the TDS1002B. I am not sure what the differences between the original and B models are though.

EDIT: From what I can find the only difference is the update in the communications port (ie. USB):
http://www.blii.com/tek/Tektronix_td...illoscopes.htm

Might be worth it...

MORE EDIT: You actually are in luck (not me though). It appears those oscilloscopes (apparently not refubrished just obsoleted due to the B model coming out) are only configured for Euro power in English or French languages (no North American power though so I'm outta luck).

Sorry, I might be confused. Maybe what I thought go no go was is not really. I think it's called mask.
What I was talking about is something you cam see in the first page of this datasheet.

http://cp.literature.agilent.com/lit...989-2235EN.pdf

the top right image on top of the scope, where you can define a short of range around the wave, and if the capture wave "goes"
out that range / limit, then it detects it. I've seen it too in one of the cheap scopes I posted before. I think Tek doesn't offer it... I don't know if it's that great but it seems cool.

I've since decided to go with an updated Tektronix TDS1001B model. There is a FAQ on the Tek website about what is different between a TDS1000B/TDS2000B and a TDS1000/TDS2000 and one of them appears to be that the newer models have an extra knob used to set stuff and controls (kind of like a direction pad). It's B/W screen though with 40Mhz and 500Ms. BUt the warranty is 10 years or +5 years after obsolence.

If you get a non-B model the warranty is only 3 years (then again for a little cheaper than the same price you do get higher sampling rate and bandwidth and a colour screen).

I've used an Agilent mixed signal scope before wit the knob with this and I really liked it.

I would not get a colour screen for 250 euros- that is equal to like $350USD or $350 CAD. I am a bit confused because the euros is worth more than the US and Canadian dollar, but whenever you mention a price you always mention a number comparable (or greater) than the dollar when it should be less since it's worth more? SO if I take everything you are saying literally your prices are far more than mine. (FOr me, getting a colour screen on an obsolete model costs $170 more). At $170 it's either or for me.

I just wish the Tek scopes could measure duty cycle so you wouldn't have to calculate it yourself because lazy am I. (and higher bandwidth and sample rate with a colour screen and logic analyzer for less money is great too).

It's way to easy to need an oscilloscope with >200MHz bandwidth for measuring digital. I'd be hard-pressed to be working with an Analog signal that requires a bandwidth of more than 1MHz. The only signal that comes to mind that I would need more 100MHz bandwidth or more for is the clock signal on a processor. I'd need a 100MHz bandwidth to measure fastest sinusoid (80-100MHz) from an oscillator that a dsPIC can handle. If I wanted to measure a square wave at that frequency the bandwidth would be x5 at least. As soon as you start measuring square waves, you need way more bandwidth.

So yeah, it's kind of understandable that if you are used to working in digital, then a 40MHz scope might seem to be too low bandwidth, but it's quite high for analog -definately way higher than needed for audio, radio, and most sensor applications (the only thing it might be too slow for that immedately comes to mind is some kinds of RF).