Test equipment

"Wayne C. Gramlich"


Thanks for the hint. I have a few xtals at home that I'll use to test it as soon as I receive it.
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http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&itemu35898356&ssPageName ­ME:B:BN:US:1
And now you're going to be spending another $50 or $75 for the probes and manual that aren't included. ;-)
- Rich
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user wrote:

If the scope works, he won't need the manuals -- he ought to be able to figure out an analog scope without them. Probes aren't very expensive these days.
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On Sat, 06 Aug 2005 09:58:34 -0500, The Artist Formerly Known as Kap'n Salty

Someone who has never used a scope before is going to need a manual, without question, if he's planning on doing anything more than measuring voltage, I expect.
And yes, probes are cheap, but you generally get what you pay for. A decent probe set rated to 100Mhz is going to cost about what he paid for the scope in the first place.
Which isn't to say that he didn't get a good deal - personally, I still use my 465. But I hope he's not just planning on sticking some wire into the probe sockets and expecting it to work. ;-)
- Rich
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My experience with oscilloscopes on Ebay may differ from yours.
I frequent a number of surplus locations where I see a significant number of used oscilloscopes purchased by bottom feeders with only one purpose in mind...to sell on Ebay. The condition, completeness and capability of the scopes vary but they all go to that great dumping ground of the Internet...Ebay.
My point is that if you buy any used electronics on Ebay, factor in the very real risk that it will likely have something wrong with it. Oscilloscopes are one of the basic tools for electronics development and they are usually kept until they are either not able to be repaired or the parts for them are unavailable. They are usually stripped of any accessories or probes (yes, good probes cost real money) and dumped on the surplus market. I would test before I would buy or get a GOOD money back guarantee before spending your money.
As for how much bandwidth a scope should have, a rough rule of thumb is 2x the highest frequency of the circuit in question to see glitches. In robotics development that is usually the microprocessor frequency. A digital scope can be used as a poor man's logic analyzer. And in digital development a logic analyzer is as important as a oscilloscope.
TMT
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"Too_Many_Tools"
<snipped>

I figured that out when all ebay ads say something like "I don't know how to test, so I don't know if it's working or not." pure crap. What I'm hoping for is to get this oscope for $70, and spend a maximum of $100-$120 fixing it (assuming it is broken). Then spend another $100 on accessories (probes and what not). I'll have spent about $300 for a good oscope (assuming it is broken and it is fixable for less than $100) for around $300. As I said in my first post, that's my budget. I have 3 options: a used tek 100MHz, a new goldstar 20MHz or no scope at all. I went for the first one.

In my company, we have around 20 oscopes, being that only half of them actually work. Some of them are quick fixes, others are more complicated and not worthy of fixing. I really hope I got one that either is not broken or is cheap to fix.
Thanks for all the replies..
All let you guys know how its state when I receive it.
Padu
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Ok, continuing the saga "Help Padu to find a decent oscope":
On the most recent episode, I bought a 100MHz 2-channel Tektronix 465M from e-Bay. It arrived sound and safe, but when I turned it on, instead of a flat line trace it showed a curved trace, very similar to a nike logo. Additionally, there are more than one trace visible at any time (no voltage or measuring a signal). I've injected a sinusoidal and it shows the wave, but more than one trace (5 or 6) at the same time, no matter what mode (AC, DC, LF, HF).
Last week I sent it to a local repair shop, it will cost $195 to fix it, I bought it for $100 (still it is less than $300, probes not included). I may go ahead and tell the guy to fix it.
On the other hand, he offered another deal. He has a 50MHz Tektronix 5440 with 2 plugins. He says it is not as portable as the 465M, but I don't care for portability given that it will not take all my workspace real estate. If I buy it from him, he will take my 465M as a trade in.
So here are the two options that I have:
1-Spend another $190 and have my 465M fixed (100MHz)
2-Spend another $145 and get a 5440 with two plugins (50MHz)
Keep in mind that I will rarely work with more than 40MHz speeds on my microcontrollers... if that says anything.
Which option should I go with?
Cheers
Padu
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Padu wrote:

Padu:
Frequencies keep creeping up. For example, it used to be that Microchip topped out at 20MHz. Then they crept up to 40MHz and now they are at 48MHz. 5 years from now, it seems probable that frequencies will be higher still.
Personally, I'd go with option 1. Getting a working Tek465 for a total expenditure of $290 is an *excellent* deal.
-Wayne
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Wayne C. Gramlich wrote:

I second that. Even if you're only working at 20MHz, the faster scope would probably be better. For a 20MHz clock (square wave), the first harmonic is already at 40MHz. In other words, your scope should be much faster than your signal in order to really see what is happening. For $50 more, it sounds like a good investment.
Good luck, Daniel
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D Herring wrote:

I'll third that. Think of scope frequency as resolution -- the greater the better.
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wrote:

I don't know about those particular models, but I'll offer a dissenting opinion.
While twice the samples has its advantages, I think 50Mhz has enough headroom to grow with a hobbyist. Even if you're using a 50Mhz processor, the signals you'll generally look at are far slower.
If the 2nd scope is dual-trace, that might be useful. Being able to compare two signals is useful when you're debugging because you can compare the signal going into and coming out of a component to see whats happening inside.
Mark
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"Mark Haase" wrote

The 465M has two traces also. The only advantage I see with the 5440 model would be price and the possibility of having different pluggins, ow and a bigger screen... I'm not sure what types of plugins are available or if they would be of any use to me or how easy is to find them (they say it is compatible with the 5000 series plugins). The 465M is a military spec dual scope 100MHz. They say that because it is a military spec it is more ruggedized. What they mean with that I don't know.
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Hmm. I don't think I understand what "2 plugins" means then. A larger screen is nice, but military spec is nicer in my book. Have you seen both side by side? $45 isn't that much in the grand scheme (although for a student it is, I know that too well) so I'd say just go with your gut.
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[snip]

Excepting, of course, that the harmonics of a square wave are _odd_, so the first harmonic is at 60MHz, second at 120MHz,...
I would ask: would you benefit from very high sensitivities? Or from being able to display many channels of information at once? Then the 5440 might be a better buy. I'd check CRT intensity, though. How much life is left in either unit?
    -frank
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