Tek 2445 for TDS 1002?

I am considering trading in my Tek 2445 analog oscilloscope for a digital one in the TDS 1000 series.

Basically for size and weight savings, as well as direct readouts and FFT.

Most of the work I do is audio, but sometimes employ 200-300V for tube work.

I assume others may have gone this way. Could I have a few opinions, even if on anlog vs. digital in general?

What, if any, limitations would I notice in making this change?

Thank you very much,

Kevin Hope

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Kevin Hope
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"Kevin Hope"

** I strongly advice you to KEEP your analogue scope !!

For audio work and other general analogue work, they are far superior.

Analogue scopes are intuitive to operate, present all waveforms in REAL time, the bandwidth is fixed instead of changing with the time base setting, there is no aliasing to drive you nuts and most of all, the CRT trace gives far more detail, resolution and information about a waveform than an LCD screen.

Obviously, a good digital scope can do things an analogue cannot (and vice versa) - so owning one of each is best particularly if you need waveform capture, signal averaging or on screen measurements of time and voltage etc.

A colleague loaned me his Tek TDS210 scope a while back, for a test drive for a week or so. I honesty tried *very* hard to get used to it - but to no avail.

The image quality on the LCD screen was, IMO, appalling. Known clean sine waves always looked to be infected with noise and even crossover like distortion artefacts. It was many times slower to use due to constantly having to fiddle with the settings and I regularly had to go back to my usual 50MHz analogue scope to check if what I was seeing was for real. Most often is wasn't.

Having spent nearly 40 years using and trusting ( therefore acting immediately upon ) what I saw on the screen of a scope, I found what the TDS 210 was showing me was not at all trustworthy for my purpose - audio design & servicing.

You mileage may vary, but do try to get a "test drive" for a least a few days on *actual work* BEFORE laying your dollars down or parting with that lovely analogue scope.

........ Phil

Reply to
Phil Allison

If you ever need good common mode rejection, you'll be much happier with TDS3000 series. The bottom-end DSOs from Tek don't seem to have much CMRR. Good deals can be found on older TDS3012s, for example.

I switched to DSOs as soon as sampling rates of a gigahertz and higher became available at a reasonable cost, and I'd never go back to analog now. A lot of the opinions you'll read are based on experiences with sampling rates of a few 10s of MHz, where aliasing can be a real problem. I kept an analog scope for a few yrs, but never used it, so sold it before it became totally valueless. One other thought: If you do low-level signal work, in the millivolts and below, then there's definitely still a place for analog scopes, also. Paul Mathews

Reply to
Paul Mathews

"Paul Mathews"

** Really ?

The TDS 1002 scope is virtually the same as the TDS 210 that I "road tested".

Ailiasing is a major problem despite the advertised 1 GS/s spec.

The reason is simple and given in the operator's manual.

When set for 5 milliseconds per division, the actual sampling rate is only

50kS/s.

So ailiasing starts at 25 kHz.

Big problem.

......... Phil

Reply to
Phil Allison

Look I have to agree with Phil, DSO's do feel quite different to an Analog scope I have both and tend to use the DSO more as a portable (it is a TDS210 and is lightweight and easy to carry), where I need to capture waveforms, where I want to look at what happens before a trigger and other odds and ends like that and use an Analogue for most other work.

Bear in mind that a DSO can give you aliasing problems as the Sample rate does vary with the sweep speed - In fact the Users manual for the TDS 1002 specifcally has a section on this issue (Download the Manual for the TDS1000 and 2000 from the Tektronix website pages 20 to 23 deal specifically with aliasing). I have to admit that even though I am familiar with aliasing it has still caught me out on occasion even though I have by and large developed the habit of double checking signals at different sweep speeds to get around aliasing

Of course DSO's do have their uses and the capture facility is great for looking at non repetitive events such as pulses and digital signals (although I also tend to use a logic analyser when I am getting into more detail with Digital issues) and if you can get used to there quirks they can do a fine job. But you do need to remember that a DSO is a different Beast to an Analogue scope and does handle things differently. in fact the DSOs real strength is in its storage capability and the Persistance mode can be quite usefeul for comparing repetitive waveforms.

If you are used to an Analog scope then For goodness sake do not go out and swap your analog scope for a Digital one - it will probably drive you insane.

If you have uses for a DSO and are used to an Analog one then I suggest you do what I do and have both - You can make your mind up later which one you prefer if you only want to keep one but do not commit to a DSO until you are used to one and by this I mean have used one for a while not just bought one home and plugged it in. Might I also suggest if you wish to go Digital that you try some of the DRT (Digital Real Time ) Scopes as they do have more of an Analog feel than the normal DSOs - although they do still have aliasing issues etc and I strongly recommend that you get used to one before you replace your analog scope.

Regards Richard Freeman

Reply to
Richard Freeman

Hmm. Let's see. 5ms/div, choosing 20kHz (to make the arithmetic easy) each cycle occupies 50us/5ms/div = .01 divisions. So, on you analog scope at 5ms/div, any 20kHz content shows up as a blur, and you need to switch to a faster timebase to see it. The same thing is true for a DSO. The limitation, for the analog scope, is mostly trace width. For the DSO, it's the number of points they show on the screen, not the sampling rate per se. I had a TDS210 about 10 yrs ago, and found it very useful, within its limitations, which is exactly how I'd describe any instrument I use. The wise DSO user always views the signal at a variety of timebase settings, just to make sure that he/she understands what's really going on with a waveform, and the same is true for analog scopes. Is that just a blur, or is there high frequency content? Paul Mathews

Reply to
Paul Mathews

Yes indeed, it sounds plain stupid to build an oscilloscope that way. Is Tektronix cutting corners? Nowadays you can expect a digital oscilloscope to have enough memory to store at least 1M points so lowering the sampling rate only occurs at very low time/div. settings (which should change the anti-aliasing filter accordingly). IIRC the

54 series HP / Agilent oscilloscopes work that way.
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Nico Coesel

snipped-for-privacy@puntnl.niks (Nico Coesel) wrote in news: snipped-for-privacy@news.kpnplanet.nl:

I suspect that the HP/Agilent 54 series isn't priced as low as the TEK TDS1002,nor are they in the same general class of instrument.

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Jim Yanik

"Paul Mathews"

** Here come a whole pile of smartasre bullshit for sure.......

** Not a blur - but very fine detail that is obviously a high frequency signal superimposed.

The context of the measurement task makes the user aware if the HF is as intended or not.

** WRONG:

What do this clown think ailiasing is?

** Go read my reply to the OP - this time carefully.

I hit each of these matters hard.

** Utterly meaningless.

** How f****ng tedious.

A service tech trying to make an income cannot afford time wasted by a scope that shows him trash - making faultless items seem to be full of faults.

** Utter bullshit.

Analogue scopes do not produce ailiasing.

The useful bandwidth is not a function of the time base setting.

The trace is sharp and clean and reveals far more info than a grainy LCD screen ever can.

....... Phil

Reply to
Phil Allison

Actually, it has more to do with the number of pixels available in the LCD than with the amount of available memory. I stand by my comments, and I have access to a great variety of scope models from Tek, Agilent, and LeCroy. I also have written many DSP applications. Most modern DSOs save so much time, that it's no real inconvenience to double-check for possible aliasing in new situations. Paul Mathews

Reply to
Paul Mathews

"Paul Mathews"

** Another "know all" code scribbler - who has totally failed to comprehend the significance of that fact the OP specified he worked on audio and tube gear.

Likely never seen any.

....... Phil

Reply to
Phil Allison

Absolutely correct Paul, that's the point: choosing 20kHz (to make the arithmetic easy) each cycle occupies 50us/5ms/div = .01 divisions.

I have the 2465B handy, but for low frequency (audio gear and tube work), I have had no case where it was necessary to have so much BW.

The DSOs like TDS, etc. are nice for audio, for single events and in genral if you have to document stuff: interfacing to a PC or laptop is easily done.

Like with all technical gear, one has to know *how* to use the different scopes - and most of us needed some time to get the change from analogue scope to DSO and feel well with it.

Some of us will never make it ;-)

just my 2 cts. of opinion

hth, Andreas

Reply to
tekamn

It a different class of scopes. Not even the analogue to digital features. Also the "look & feel" of the handling.

Downloading & studying the tektronix "abc of oscilloscopes" helped me a lot to understand Teks philosophy and get used to the scopes from Tektronix. Maybe it is helpful for you too.

hth, Andreas

Reply to
tekamn

The wise user almost never takes the scope out of "envelope" mode, which in my scopes runs the digitizer at full speed and plots a vertical line from the highest to lowest values within one display pixel. While this smears out the signal slightly in the vertical direction, it's otherwise very much like using an analog scope that can look backwards in time. Aliasing is not a major problem, and you get an accurate indication of the limits of the measurement resolution.

I've seen too many strange waveforms that turned out to be caused by some nasty tarting-up algorithm inside the scope.

Cheers,

Phil Hobbs

Reply to
Phil Hobbs

A DSO is very usefull for low frequencies. You'll have a stable flicker-free picture.

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Nico Coesel

"Nico Coesel"

** No problems in the audio band .

Still very usable down to 5 Hz and less with a standard persistence screen.

......... Phil

Reply to
Phil Allison

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