First oscilloscope

How much money do you have to spend?

Ideally you want two of them. A good traditional analog oscilloscope, and a digital storage oscilloscope. To analyse the output from IR remote controls requires you to capture and display the signal, this requires a digital storage oscilloscope. However the requirements of this are very simple and could be covered with a cheap USB PC oscilloscope.

With both types you pay more for more *analog* bandwidth.

60-100MHz is a good starting point these days. With digital oscilloscopes you pay more for *sample memory* and sample rate. The more sample memory the better. Ensure that the sample rate is at least 10 times the analog bandwidth. e.g. a 100MHz bandwidth digital scope should have a 1GS/s sample rate. A good size sample memory starts at say 8K and goes upwards. You get much better value-for-money with a second hand oscilloscope from Ebay or a surplus dealer, especially for analog types. e.g. you'd be a bit foolish to buy a brand new 100MHz analog oscilloscope, they are expensive. But brand new 20MHz dual channel analog scopes are fairly cheap these days, that is a decent starting point. With eBay you take your chances somewhat, but buying from a reputable dealer who has extensively tested (and possible calibrated) the unit can be a good way to go. Digital scopes are fairly expensive, and the second hand market is not big, but if you have the money then get a good one over a USB based PC oscilloscope. You need to buy a very expensive digital scope to get good "analog like" performance, that's why I recommend getting a good analog scopes too.

Dave.

A sound card based PC Scope would be ideal. The P/H to buy a even the cheapest Hardware Scope would exceed the cost of the software for a PC scope

The IR remote runs around 15 KC so using a 100Mhz Scope would be like using a 4 engined Water-Bomber to water the Lawn. Effective, just not cost effective. Digital would be nice, but again it's like using a Micrometer to measure cut firewood !

The 433Mhz PIC is just a Red Herring ! Yukio YANO

How do you know that? 433 MHz is used for remote controls, and garage door openers.

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Get any decent secondhand Tektronix.

You can't go wrong with a Tek, much as the same way you can't go wrong with a Fluke DMM.

Graham

Rubbish, it would be the worst possible solution. You at least need a proper front end amp/attenuator for such a thing, and even then you are limited to audio bandwidth only. Unless the OP's "analog circuits" are all audio bandwidth and line level type signals, forget it.

Hardware scopes can be had for FREE if you look hard enough. People (including myself) have given away scopes for free before on this and other groups. Beginners can ask and they often get a lucky donation.

Wrong. They are around 38KHz.

That's not the point. The point is having a general purpose tool that can do all sorts of jobs.

100MHz is not overkill for a general purpose scope. Want to measure a basic 20MHz digital signal for instance, 100MHz comes in handy.

Digital is essential jobs like capturing IR data packets. A logic analyser is often handy for this too.

Ah, 433MHz is used for all sorts of stuff.

Dave.

Hi all,

Thanks for the informative replies - lots to think about!

Unless there is a kind person out there who wants to hand me a hardware scope I think the best option would be a USB PC scope. It'll allow me to do IR analysis which is what I really want to look at for now and should allow me to analyse more basic circuits. If I reach it's limitations I can look into a more expensive (digital) solution.

Which brings me onto my next question - what USB scopes are out there and which make(s) are worth considering??

I'm still a bit unsure on the bandwidth issue....if IR runs at 38Khz then a 25Mhz scope should be able to see the signal very clearly shouldn't it? Also, the maximum speed I run PICs at is 20Mhz but that's divided by 4 to give a real speed of 5MHz. If the output signals actually ran at this speed (unlikely because it wouldn't give the PIC time to do anything else, would a 25MHz scope be able to display them?

Thanks

Gareth

Not a bad idea.

The question is still how much would you be looking to spend?

To analyse IR data packets you might need a reasonable amount of sample memory. 8K is probably the minimum you'd want to look at, but the more the better. Some USB scopes might sample in real time to the PC, so they could effectively have have unlimited sample memory (at lower sample rates)

Yes, it's plenty.

25MHz bandwidth - yes 25MHz sample rate - that's starting to push it.

Dave.

A 25 Mhz is just fine. try to get a stand alone bench or hand held that has the PC connection and software.. I my self bought a OWEN hand held for my toss around tool box scope, that's a 20 Mhz and It just happens to have a DMM also along with isolated inputs between all inputs.. $499, is what I paid for it and I find that for the price and what it does, it's great for moderate work and for most maybe even over kill.

P.S. they make a 60 Mhz version of the same unit.

For anything high in freq, I keep a Tek Analog 350 Mhz scope around for that.

"

You may want to consider having both a (used) hardware scope along with a PC soundcard program. (OK, I might be a tad biased since I am the author of one such program!) I have a 100 MHz "real" scope plus a sound card system on my bench, and they both have their virtues.

The hardware scope is best for all general purpose work. The sound card system suffers from being AC coupled, and limited to audio-range signals. But if you are working in the audio range, there are some powerful advantages: It does spectrum analysis and color spectrograms, as well as all sorts of tricks like histograms, and synchronous waveform averaging to extract signals buried in noise.

If you are working on something where you need to monitor distortion, a conventional scope's waveform display is *not* the way to go: Depending on the type of distortion, you might miss several percent distortion on a sine wave display, whereas on a spectrum display you can easily see a tiny fraction of a percent. Not only that, you can see exactly which harmonics are causing the trouble (which can be a clue to the source of the distortion).

As an example, if you build a triangle-to-sine shaper using an overdriven differential pair, there are a couple of interacting adjustments that can be really confusing to adjust by just looking at the waveform (or by ear). But they are a snap if you can watch the relative harmonics go up and down on a spectrum display.

And sound card systems can be dirt cheap, especially with the easy availability of old computers these days.

And if that isn't enough to convince you, there's the fact that sound cards can also *generate* sound... with lower distortion than most benchtop audio generators, and *much* lower distortion than function generators. But they can provide much more control than any function generator, not only in offering many types of waveforms, including different kinds of noise, but also in types of modulation like bursts, AM, FM, PWM or PM, or sweeps.

(Product plug: The Daqarta signal generator is FREE, even if you never buy the system. Oh, yeah: Daqarta also includes a big-screen DMM with true RMS, peak, and dB options, plus a frequency counter that can resolve to milliHertz in a few cycles, even at low audio frequencies.)

Best regards,

Bob Masta DAQARTA v3.50 Data AcQuisition And Real-Time Analysis

Scope, Spectrum, Spectrogram, FREE Signal Generator Science with your sound card!

You can get you a vellman PC500 scope for about 300 bucks wich is suppose to be 50mhz(which is 50MSPS and I don't see how it sends all that through the parallel port which runs at most a few mhz or so).

The only reason I recommend this scope now is because they finally implemented a history function. When I first brought it I thought it would have this feature but didn't. I complained on the msg board and was told that it was impossible and I didn't understand how a DSO worked(by the company). So I gave up and 2 years later I tried again and somehow got through to the guy that maintained the software and he was able to implement it. The software is definitely not the best though but works.

So the point is that with that scope you can use it both as a oscilloscope and a logic analyzer(although a bit crude it does work). This is really the only benefit it has is that its cheap and can do the two most important things needed for most apps. It is definitely not the best though but you get what you pay for. If you have more money then I'm sure there are other products that would be better. (in fact you can get cheap dedicated logic analyzers too now that use the pc)

I would have to say that the real issue with the scope is mainly the software though. But you can get used to it and maybe in the future they will release the protocol used so people can write there own software. (they do have something like it but not full featured)