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# Low-cost oscilloscope recommendations

J

#### joshc

Jan 1, 1970
0
Hi,

I haven't been able to find a recent thread on this so I figured I'd
start a new one. I graduated with my M.S. in computer engineering a
little over a year ago and have been working in the embedded systems
world. My focus in school was real-time embedded software and the
hardware courses I took had to do with computer architecture, one
signals & systems course, digital system design using FPGAs and micros,
and digital hardware design at the logic gate level.

Now that I'm in industry I am working to strengthen my electrical
engineering skills and playing with different circuits interfacing
analog components to microprocessors/microcontrollers. I'd like to
purchase my first oscilloscope so I can use it while I play around with
circuits in my little home lab setup. It seems that a scope with a 100
MHz bandwidth should be plenty for me but I'm not too sure since I've
been reading up on trying to clarify what this really means. I'm not
entirely clear on the concept of vertical amplifier bandwidth yet since
it has to do with its frequency response and how much the input signal
is attenuated and apparently the bandwidth rating for the scope is
based on a -3 db attenuation or something.

So I'd love some help from you guys on choosing what oscilloscope to
purchase given my background above and what I'm looking to do. I've
been spoiled by my college and work oscilloscopes which are high end
tektronix and fluke scopes but obviously I can't afford those. I'm
looking for something ideally around $300 but if I have to I can go up to about$500 so based on my research it seems this would limit me to a
used, analog oscope. I've read a lot about the tektronix 465 scope so
maybe that's the right one for me but I'm looking for suggestions on
what oscilloscope you recommend as well as where you recommend buying
it from. For a beginner like myself it seems that buying a used one
from ebay might not be such a great idea since there is no guarantee
the scope works and I wouldn't know how to fix it.

Sorry for the long post but I'd like to give you as much information as
I can so you expert folks can help me make the right choice. Please
feel free to ask followup questions of me.

Thanks for your time and help,

Josh

M

#### mike

Jan 1, 1970
0
joshc said:
Hi,

I haven't been able to find a recent thread on this so I figured I'd
start a new one. I graduated with my M.S. in computer engineering a
little over a year ago and have been working in the embedded systems
world. My focus in school was real-time embedded software and the
hardware courses I took had to do with computer architecture, one
signals & systems course, digital system design using FPGAs and micros,
and digital hardware design at the logic gate level.

Now that I'm in industry I am working to strengthen my electrical
engineering skills and playing with different circuits interfacing
analog components to microprocessors/microcontrollers. I'd like to
purchase my first oscilloscope so I can use it while I play around with
circuits in my little home lab setup. It seems that a scope with a 100
MHz bandwidth should be plenty for me but I'm not too sure since I've
been reading up on trying to clarify what this really means. I'm not
entirely clear on the concept of vertical amplifier bandwidth yet since
it has to do with its frequency response and how much the input signal
is attenuated and apparently the bandwidth rating for the scope is
based on a -3 db attenuation or something.

So I'd love some help from you guys on choosing what oscilloscope to
purchase given my background above and what I'm looking to do. I've
been spoiled by my college and work oscilloscopes which are high end
tektronix and fluke scopes but obviously I can't afford those. I'm
looking for something ideally around $300 but if I have to I can go up to about$500 so based on my research it seems this would limit me to a
used, analog oscope. I've read a lot about the tektronix 465 scope so
maybe that's the right one for me but I'm looking for suggestions on
what oscilloscope you recommend as well as where you recommend buying
it from. For a beginner like myself it seems that buying a used one
from ebay might not be such a great idea since there is no guarantee
the scope works and I wouldn't know how to fix it.

Sorry for the long post but I'd like to give you as much information as
I can so you expert folks can help me make the right choice. Please
feel free to ask followup questions of me.

Thanks for your time and help,

Josh

Don't overlook obvious freebies.
Convince your boss that it's in his best interest for you to learn more.
They may have something gathering dust that you can borrow.

Go find a ham radio club. Those guys often have spare scopes for their
spare scopes in the basement. I have a spare TDS-540, if you can
believe that insanity...
mike

--
Wanted, Serial cable for Dell Axim X5 PDA.
Return address is VALID but some sites block emails
with links. Delete this sig when replying.
FS 500MHz Tek DSOscilloscope TDS540 Make Offer
Bunch of stuff For Sale and Wanted at the link below.
MAKE THE OBVIOUS CHANGES TO THE LINK
ht<removethis>tp://www.geocities.com/SiliconValley/Monitor/4710/

T

#### Tim Williams

Jan 1, 1970
0
Tek 465/475/485s are cheap and plentiful on eBay, IIRC.

Tim

J

#### joshc

Jan 1, 1970
0
Tim said:
Tek 465/475/485s are cheap and plentiful on eBay, IIRC.

Tim

Thanks for the recommendations. The problem with eBay is that almost
all of the 465s have no warranty/guarantee that they work although the
seller says they do. If I paid $300 and got a dud I'd lose my money since I don't have a clue how to repair them. Any idea of any online stores selling used test equipment? I'll look into the ham radio club thing since I've heard that before but have no clue what a "ham radio club" is and if I have any near me. Thanks. N #### Noway2 Jan 1, 1970 0 There are some on-line sellers of used test equipment, google for that phrase or for "used oscilloscopes" and you should come up with plenty. Ebay, however very well may be your best bet, though I do understand your concerns. Honestly, I don't feel that giving someone a "bad review" to be sufficient response to taking my money on a dud. While it would be possible to sue them, it would likely cost just as much. On the other hand, I know people who buy used test equip on ebay and they haven't had a bit of trouble. A word of caution against a 100 Mhz scope: You are on the right track about bandwidth limitations. The scope bandwidth will significantly influence your ability to see higher frequency signals. Modern digital electronics have very fast rise and fall times, which correspond to significant engergy in the higher harmonics. In order to acurately view these signals you need a scope with significant bandwidth. The high speed / high frequency nature of these signals is independant of the clock frequency of your circuit, meaning that a simple and - or circuit implemented with LSI chips coiuld exhibit this behavior and FPGAs, which you mention using above, tend to have 'very fast' transition times. A digital scope would also be beneficial with regards to catching and non-periodic and non repeating signals which are quite common in digital circuits. One thing to keep in mind is that I understand a lot of companies sell their outdated equipment on ebay when they are upgrading. What may be outdated for them could be a treasure for you. M #### mike Jan 1, 1970 0 joshc said: Thanks for the recommendations. The problem with eBay is that almost all of the 465s have no warranty/guarantee that they work although the seller says they do. If I paid$300 and got a dud I'd lose my money
since I don't have a clue how to repair them. Any idea of any online
stores selling used test equipment?

I don't recall ever buying a scope that worked 100%. And it's not
always obvious. Most have been easy to fix if you know what you're
doing...and you spent 20 years working for TEK. The bad news is that
it's really hard to fix a scope without a scope ;-(

If you buy used, try to get manuals and probes. It's not unusual for
a manual to cost more than the equipment did.

Dealers can charge you 10X what it would cost to buy it right
from an individual. There's a well-known test equipment refurbisher
who sells equipment on ebay under an individual user name. "AS-IS No way
to test it". I'd shy away from them, cause they damn sure can test it.
I'll look into the ham radio club thing since I've heard that before
but have no clue what a "ham radio club" is and if I have any near me.

Go here:
http://www.qrz.com/i/names.html
Type in your city and call one of 'em up and ask about clubs, people who
might have scopes for sale etc. The whole objective of the hobby is to
talk to people you don't know. They'll be glad to hear from you. Once
they get to talking, you'll probably find it hard to shut 'em up... 3
or 4 calls and you'll have a scope...depending on where you live.

Put a request on rec.radio.amateur.equipment
and
sci.electronics.equipment
and
craigslist.
mike

--
Wanted, Serial cable for Dell Axim X5 PDA.
Return address is VALID but some sites block emails
with links. Delete this sig when replying.
FS 500MHz Tek DSOscilloscope TDS540 Make Offer
Bunch of stuff For Sale and Wanted at the link below.
MAKE THE OBVIOUS CHANGES TO THE LINK
ht<removethis>tp://www.geocities.com/SiliconValley/Monitor/4710/

M

#### mike

Jan 1, 1970
0
Noway2 said:
There are some on-line sellers of used test equipment, google for that
phrase or for "used oscilloscopes" and you should come up with plenty.
Ebay, however very well may be your best bet, though I do understand
your concerns. Honestly, I don't feel that giving someone a "bad
review" to be sufficient response to taking my money on a dud. While
it would be possible to sue them, it would likely cost just as much.
On the other hand, I know people who buy used test equip on ebay and
they haven't had a bit of trouble.

A word of caution against a 100 Mhz scope: You are on the right track
about bandwidth limitations. The scope bandwidth will significantly
influence your ability to see higher frequency signals. Modern digital
electronics have very fast rise and fall times, which correspond to
significant engergy in the higher harmonics. In order to acurately
view these signals you need a scope with significant bandwidth. The
high speed / high frequency nature of these signals is independant of
the clock frequency of your circuit, meaning that a simple and - or
circuit implemented with LSI chips coiuld exhibit this behavior and
FPGAs, which you mention using above, tend to have 'very fast'
transition times. A digital scope would also be beneficial with
regards to catching and non-periodic and non repeating signals which
are quite common in digital circuits.

I can't argue with "faster is better", but it's easy to delude yourself
into thinking a faster scope will make it easier to debug a digital
thing. Analog scopes are great for periodic signals. Problem
is that your digital thing is far from periodic. Unless you can
trigger the scope on the parameter of interest, it don't matter how fast
it is. And the problems hardest to solve are the most intermittent.
I have a GAL20V8 on a breadboard with flying leads as a trigger
recognizer. I write a custom program for the GAL to optimize the
sequential event triggering to see what I'm looking for. Tedious, but
powerful.

The sweet spot of price/performance for analog scopes is 50-100MHz.
Much faster and they've got too much custom stuff inside and can't be
repaired by mere mortals. I'd vote for the TEK 465 family. 7704 mainframe
scopes can be had dirt cheap, but get 'em with plugins. Ebay
nickel-dime you into the poorhouse filling up the holes. Snag a full
system with manuals and probes.

mike

One thing to keep in mind is that I understand a lot of companies sell
their outdated equipment on ebay when they are upgrading. What may be
outdated for them could be a treasure for you.

--
Wanted, Serial cable for Dell Axim X5 PDA.
Return address is VALID but some sites block emails
with links. Delete this sig when replying.
FS 500MHz Tek DSOscilloscope TDS540 Make Offer
Bunch of stuff For Sale and Wanted at the link below.
MAKE THE OBVIOUS CHANGES TO THE LINK
ht<removethis>tp://www.geocities.com/SiliconValley/Monitor/4710/

B

#### Buddy Smith

Jan 1, 1970
0
analog components to microprocessors/microcontrollers. I'd like to
purchase my first oscilloscope so I can use it while I play around with
circuits in my little home lab setup. It seems that a scope with a 100
MHz bandwidth should be plenty for me but I'm not too sure since I've
been reading up on trying to clarify what this really means. I'm not

Here's a recent article about some of the PC-based oscilloscopes, which
seem to be a pretty good value:

http://www.ganssle.com/microscopes.pdf

ttyl,

--buddy

G

#### GTR

Jan 1, 1970
0
Although its been mentioned a number of times before, ebay is the way to go.
Just make sure you buy from a seller with 99% or above and you will likely
be fine. I bought my scope there and it cost me half of any other place I
looked. As long as it is not *collectable* ebay is a great place to buy
stuff cheap IMHO.

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