Author Topic: Why getting an analog oscilloscope?  (Read 7592 times)

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Offline james_s

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Re: Why getting an analog oscilloscope?
« Reply #25 on: May 07, 2021, 06:23:49 pm »
The main reason for a beginner to get an analog scope these days is that they can still sometimes be found for very cheap or even free. Other than that, DSOs have progressed a long way and there are very few reasons to actively seek out an analog scope anymore, the one big advantage I can think of is XY mode is still far better on an analog scope than on any DSO I've tried but that's a niche feature that most people will not need. These days there are inexpensive DSOs that are quite good so my advice is just get a DSO unless you are on a tight budget or somebody offers to give you an analog scope.
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Offline nfmax

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Re: Why getting an analog oscilloscope?
« Reply #26 on: May 07, 2021, 07:18:13 pm »
The X-Y mode on the Keysight DSOX3000T series is really, really good

Offline CaptDon

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Re: Why getting an analog oscilloscope?
« Reply #27 on: May 10, 2021, 02:22:37 pm »
For you guys who rave about the X/Y mode of the digital scopes, do they have a decent intensity modulation feature also? Any time I personally needed the X/Y feature I also need intensity modulation. I had to deal with analog character generators and vector graphics which needed 3 bits of intensity control. The older TDS stuff can't do it, all of my analog scopes can.
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Online richard.cs

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Re: Why getting an analog oscilloscope?
« Reply #28 on: May 10, 2021, 03:00:40 pm »
One of the best reasons why I keep an analog scope with 80mhz bandwidth in my rack is that they don't alias!!!...

As others have said the fact that analogue scopes never alias is very useful, every digital scope I have ever used, including some very high-end ones, alias under some conditions and it's quite easy to get confused and waste time debugging something that's not real. Analogue scopes offer the full bandwidth at all sweep rates, a 100 MHz analogue scope will happily display (as a blur / fuzz) a 100 MHz signal on 1 second/div whereas a digital scope may well alias it down to some other, possibly non-obvious, frequency. This is useful for avoiding misleading outputs, and also for things like displaying RF signal envelopes.

XY mode just seems better on analogue scopes, I have a suspicion it's either that it's just an afterthought on digital scopes or that they make some dubious assumptions about expected signal frequencies in that mode.

The availability of magic 'Pause' function. It's the killer USP.... the painless capture of non repetitive signals.
This. This is why I use a DSO most of the time. Right up until I get something odd happen when I whinge unfairly about DSOs and go get an analogue scope out to confirm if it's real or not.

DSOs are getting a lot better at analogue-like displays, with useful gradients, persistence, etc. Infinite-persist is another useful DSO USP.

Offline SuzyC

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Re: Why getting an analog oscilloscope?
« Reply #29 on: May 10, 2021, 03:49:11 pm »
If I try to display in real time slow events or low-level signals at low frequencies, my analog two-channel 20-MHz oscilloscope is an essential instrument. On the digital scope I have, the same task is very difficult, hard to set up, and annoying to wait for triggering.

On my 200-MHz DS4024, if I want to see what is actually happening and if I set the time/div at 1-Sec/div, I must wait for the scope to accept a trigger to get a sweep to start and then the display will be delayed up to 14-secs before the scope will show anything on the screen.
I might even have to wait up to another 14-seconds before I can get the digital scope to trigger again. This is very frustrating.

As a beginner, I would most often like to see cause versus effect. If I spoke into a microphone and adjusted any component of a simple 1-transistor amplifier, and attempted to probe the signal into the transistor on one channel and also probed the output on the second channel, I would immediately see everything happen immediately as it happened and this really helped me to understand how circuits work.

I could also set the intensity of a free-running display to have a really thin, sharp line. This means I could explore every point on a circuit in this free running mode(i.e. 10mSec/div)  and visually measure them at a glance.
Because I can see all the voltage levels instantly. I am able to measure them quite accurately using the scope graticule alone and I don't  have to use my DVM.  What's more, the 10x probes of the scope would not upset the circuit I am working on like the long unshielded probes of the DVM would.  The fat trace on a digital scope often overwrites the simulated graticule, and since the trace is thick, the digital scope greatly diminishes the at-a-glance accuracy when I want a quick visual examination of all test points of the project I am working on.

And if I wanted to see tiny signals at 1-mV per division and trigger on them I could easily see them clearly on my analog scope. This is impossible on my digital scope, triggering is very poor or non-existent when attempting to view low-level signals that have an amplitude of only one or two minor divisions. Auto-triggering on my digital scope is often just a joke.

When I trigger a signal on my analog scope, it displays the signal until the end of the  viewing area and keeps the displayed waveform
only for the spit-second persistance of the display.

The digital scope has infinite persistance with normal triggering, and even after I remove the probe, the signal is displayed.
This can cause me to think a signal is present when it is not.

When is comes to viewing with power supply D.C. levels, low voltage signals, and low-frequency audio, the analog scope is undeniably the best.

When I first started to learn electronics, I able to learn quickly because I could use my analog scope for all my simple experiments and clearly see signals with just a slight tweak of a triggering level knob and unlike my digital scope, not require me to turn several switches and push a half-dozen buttons to see what was going on in my experimental circuits.

Many  years later, when I began to work with MCU's a digital scope was essential, for example, to single-sweep and hold a complex 4-channel display of simultaneous digital signals, or even to just viewing an RS-232 bit stream, but the need for this digital instrument was long after I first started to play with and learn the workings of electronics.

I still use both scopes and really appreciate the convenience of use and clean display of my analog scope and the necessity of having a digital scope for troubleshooting and developing the really complex robotic projects I am playing with now.
My digital DS4024 now sits on top of my Hong-Chang 20-MHz and it fits perfectly, like a saddle on a horse. This is very important, because it raises the DS4024 to a much higher viewing level and makes it so much easier to see the display without hurting my neck!
« Last Edit: May 10, 2021, 04:25:27 pm by SuzyC »

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