my first oscilloscope

[jrz126]

Ok gang,
I'm thinking about buying my first oscilloscope and I need your help.
I know I want to go digital (possible PC-connection for easy data storage (depends on price)).
What is a good frequency to get? I know I want above 20mhz, but whats a good max to have. I'm just going to be doing simple stuff so I wouldnt need anything too crazy.
I'm loooking to spend about $300, but if I can get a good deal on one, I'd concider spending more

I'm going to keep my eye on ebay, and I'll post what I think looks like a good scope.

I'm going to ask around at work and see if maybe they sell their old equipment. we will see.

EDIT: After looking through ebay's auctions it looks like I'm going to have to spend a little more for a good working digital scope. I found this one here, it's got 5 days on it, so I doubt I'll get it for anywhere near the listed price, but anyhoo...**broken link removed**

 

[stevez]

I am not the expert on this subject but noticed some differences in the way specifications are presented for 'scopes. The traditional stand alone scope is often described in screen size and frequency - my understanding of frequency meant the highest frequency to be input or measured with the scope. I've also seen many of the newer portables and PC based 'scopes listed by frequency and on closer inspection the frequency appears to apply to sampling rate. If this is true then a 20 mHz description could mean vastly different things - with a 20 mHz sampling rate you'd have 10 samples of a waveform at 2 mHz which may not be what you want.

 

[panic mode]

...and number of channels...
It's time of 100MHz+ scopes. Anything less should be a bargain.
I would check eBay or if you want to build your own check bitscope.
It's a small but powerfull scope that connects to your PC.

 

[zachtheterrible]

im no expert on scopes, but that there looks perdy nice :lol:

if you want to do a lot of digital, make sure that you get a scope that is designed for . . . i think its called slow moving or non-repeating signals. this means that if you want to look @ the pulses from ur tv remote, the scope will store the signal so that you can "pause". but im sure u already knew that :lol:

 

[williB]

1 GHz my gawd..it makes mine look like ...well really old..
anyway i saw a project on piclist.com it was a Pic O ' Scope or something like that ..
very nice , with output on the pc screen...

 

[Digi-D]

scope q

Has anyone used the bitscope? It seems pretty nice for the price and the features.

I'm currently looking at:
**broken link removed**

Can anyone recommend/steer away?

thnx
d

 

[Dean Huster]

The Tektronix TDS 210 is an excellent little digital scope. I've used a TDS 220 a lot and really liked it. One thing that you won't find on any other digital scope from any company other than Tektronix for a scope at that price level is the 1 GS/s sampling rate. I believe the main difference between the TDS 210 and the TDS 220 is that the latter has a 2 GS/s sample rate. The scope should have two memories on-board. You can buy plug-in modules to add GPIB (IEEE-488, i.e., HPIB) interface, RS-232 interface or a Centronics printer interface. Shop carefully for these modules, because you could end up spending more for the module than you do for the scope on ebay! The TDS 220 was originally introduced by Tek at a price of around $900, quite incredible considering that the original 15MHz T922 sold new for $1800 back in 1976 and the TDS 220 far outperforms the T922 in every way.

Dean

 

[jrz126]

So does that scope that I was looking at on ebay seem like a good deal?
Also, is this scope only capable of 60Mhz? Should I buy it if I can get it for less than $500?

 

[Nigel Goodwin]

So does that scope that I was looking at on ebay seem like a good deal?
Also, is this scope only capable of 60Mhz? Should I buy it if I can get it for less than $500?

As far as I'm aware they are good scopes, I'd certainly like one!.

But i would suggest you evaluate what you need a scope for, certainly this sort of price range is a lot of money - a much lower spec scope will do 99% of what you need for a fraction of the price.

If you've never owned or used a scope, a simpler one is probably better to start with.

A 20MHz double beam scope will do almost everything you ever need, a digital storage scope might be helpful very occasionally, as is a higher bandwith - but only very occasionally!.

Do you have a specific use in mind?, or is it just a general purpose scope you're looking for?.

 

[williB]

Re: scope q

Has anyone used the bitscope? It seems pretty nice for the price and the features.

I'm currently looking at:
**broken link removed**

Can anyone recommend/steer away?

thnx
d

I just want to say that i have allways liked the idea of using an A/D converter hooked up to a PC for an oscilliscope...
there have been many times when i could have used the storage capabilities , to see signals that dont repeat...

 

[jrz126]

Nothing specific, I'm just looking for a general scope that I can use for average tasks (I'm more into digital circuitry if that has any effect on the decision).
Now that I think about it, it is a lot of money, although it's only a 2 week paycheck (42 hours total). Maybe I'll look into getting a cheaper scope, and a good DMM. How much do those autoranging ones usually run for?

I'm going to talk to some of my profs tomorrow and see what they recommend.

Also, I picked up one of those portable scopes while i was volunteering at a second hand store about a year ago, someone stuffed it away in the back, so I got it for about $1.00. It's battery powered but the battery isnt there. I have the instruction manual (which has a schematic of the entire unit, even tells you what voltages you should be getting at different nodes.) I tried putting power to it, but the power switch seems to be bad, I jumped it out and got it to turn on. so the tube works? (i got it to show a dot, I don't think I could get a sweep out of it?).
The instruction manual gives a bunch of detail on how to recalibrate it, so I think I would be able to get it accurate again.
theres one up for auction on ebay **broken link removed**
so should I seriously look into getting it to work? What usually goes bad/needs replaced on old equipment like this?

 

[Nigel Goodwin]

Nothing specific, I'm just looking for a general scope that I can use for average tasks (I'm more into digital circuitry if that has any effect on the decision).

The BIG advantage of a storage scope is that you can freeze a non-recurrent event, a good example is the output of a TV remote control. It's very difficult to see it reliably on a normal scope, with a storage scope you can freeze the image and examine it at your leisure.

Now that I think about it, it is a lot of money, although it's only a 2 week paycheck (42 hours total). Maybe I'll look into getting a cheaper scope, and a good DMM. How much do those autoranging ones usually run for?

I'm going to talk to some of my profs tomorrow and see what they recommend.

Good idea, they will probably be able to advise you, and may even know someone who's selling something suitable!.

Also, I picked up one of those portable scopes while i was volunteering at a second hand store about a year ago, someone stuffed it away in the back, so I got it for about $1.00. It's battery powered but the battery isnt there. I have the instruction manual (which has a schematic of the entire unit, even tells you what voltages you should be getting at different nodes.) I tried putting power to it, but the power switch seems to be bad, I jumped it out and got it to turn on. so the tube works? (i got it to show a dot, I don't think I could get a sweep out of it?).
The instruction manual gives a bunch of detail on how to recalibrate it, so I think I would be able to get it accurate again.
theres one up for auction on ebay **broken link removed**
so should I seriously look into getting it to work? What usually goes bad/needs replaced on old equipment like this?

I've never seen one, but if you can get it working it will be very useful, ANY scope, no matter how poor, is just so useful - I've been using one of mine today, checking the Icon Designs Mixer I asked about in another thread!.

 

[panic mode]

Any (working) scope is better than no scope but if you can get hold of DSO that's what you should have nowdays. The one in top of tread is same family as what we use at work. They are excellent products.

 

[williB]

I should seriously look into getting it to work?

you should definatly try getting it to work..

 

[jrz126]

The reason I didnt try to get it working before was because I didnt know what I was doing, but now I have some Electronics experts at my disposial, so it should be a piece of cake.

I'm going to take it to school with me someday and tear into in one of the labs. Maybe I'll show it to my profs and see what they say about it, maybe they'll give me a hand.

 

[jrz126]

I'm looking through the manual right now, They give some powersupply voltages to check, there are some high voltages in there from the CRT. Are these high voltages stored anywhere? or does it discharge as soon as I turn it off? If I'm going to be playing around in there, I dont wanna shock myself.

I'll probably scan the schematic and post it later today.

 

[Nigel Goodwin]

I'm looking through the manual right now, They give some powersupply voltages to check, there are some high voltages in there from the CRT. Are these high voltages stored anywhere? or does it discharge as soon as I turn it off? If I'm going to be playing around in there, I dont wanna shock myself.

I'll probably scan the schematic and post it later today.

The highest voltage will be feeding the final anode of the tube, as it's only a small CRT it probably won't be more than 1-2KV?. It's certainly likely that things will stay charged up, but if you have a spot on the screen and no horizontal scan it's likely that the timebase isn't running. It's also possible that you have the controls set wrong!.

As you have the schematic that should make things a LOT!! easier.

 

[zevon8]

That little scope is quite useful, we had some of them years ago when I worked for an industrial maintenance firm. This was before the days of LCD 'scopes like Fluke makes now. The only problems we ever had were the batteries going bad from improper charging cycles ( NiCad memory ) and the switches having bad connections. Some had toggle switches the others had slides like in the picture. I would check and see if one the slide switches has failed. I think you may find that there is no horizontal sweep in this case because the time base signal must pass through these switches. The triggering can be a little odd on these also, some models will not sweep without an input signal.

Schools / Universities can often be a great source of test gear if you can contact the right people. Many times the equipment they have is of excellent quality, state-of-the-art for its day, and often has been kept in calibration under maintenance contracts.

I fully agree with the rest of the posts, any scope is better than none. I would say that a large percentage of testing involves " is there a signal , and if so does it sorta look like what I think it should ?" Often you don't even really measure it, you just need to "see" it, and be able to tell if it is in the right relative proportions of duty cycle or shape. So much information can be gathered in a quick look at a signal that often a truely accurate measurement of all its characteristics is not needed. Of course, the more features you can get the better, but a basic instrument often is suffice for a large percentage of work. I used to have an old Eico / Heathkit 500 Khz AC only tube scope that was superb for audio work with its very thin trace. You could only make relative measurements, but I bet I used that scope more than my others at the time, even though it was more than 30 years old.

 

[Dean Huster]

I have used several digital scopes, beginning with one of the first high-speed digital models (Tek 468) and several others since then. I don't own a digital scope. I own several analog models, all Tektronix (the 212, 213, 465DM44 and 7904 with plug-ins). Other than waveform storage, there's virtually nothing that my analog scope can't do that a digital scope does. Yes, the DSOs often will display actual voltage and time on the screen -- but I know how to read those things on my analog scope. I don't have finite stair-step jumps on my analog display and I can view a single-shot 400MHz pulse where most DSOs under $20,000 fail. If I need to record a waveform, I can use my scope camera, although the Polaroid film is getting increasingly difficult to find. However, I've found that the only reason I've ever had to record a scope displays is for illustrations in the curriculum I write.

The point is this: don't let anyone tell you that a DSO is the only way to go these days. You can find lab-grade analog scopes (def, "Lab Grade": high-end, high-performance scopes we could have only dreamed of having 20 years ago) for under $500 that will have 500MHz bandwidths. If you can find a working 100MHz DSO for under $500, it's a bargain if it isn't more than 10 years old.

Also, beware of what is digital and what is not. A Tek 2465 is a top-end portable analog scope with a lot of digital enhancements, but it's not a DSO.

Dual-beam is a scope with a CRT that has two independent deflection systems and can display two simultaneous single-shot events at one time. Dual-beam scopes (e.g., the Tek 7844) are rare these days. Nearly all scopes are dual trace, the CRT being time-shared between two signals. Now, most digital scopes are the equivalent of dual-beam scopes if they have two independent sampling systems that don't suffer slower clock speeds as channels are added. But a DSO still has a very difficult time resolving single-shot pulse edges.

For the same price, you can get higher performance and bandwidth on an older analog scope than you can on a newer digital scope. It takes time and technological generations to bring the price down on DSOs.

Dean

 

[jrz126]

Well, I finally got around to asking my professor about a scope. He suggested ebay He also said that the school isnt ready to upgrade, and even if they were, the scopes are pretty beat by that time.

He also said that there is an electronics place in Cleveland that sells used scopes, he couldnt remeber what the name of the place was, he thought it was like amater electronics or something.

Optikon, I notice that you are from there, do you know anything about this place? (i also sent you a PM onm it )


It's alittle more than an hour drive one way, but it might be worth it so that I can see what Im spending my money on.


Oh yeah, and now I really want one, I spent an hour or 2 debugging my circuit to figure out why it wasnt working...turns out my 555 timer went bad? If i had a scope, I would have found that problem in 5 minutes