Oscilloscopes

What's the best scope to get for the money for mostly digital circuits? I'll have some analog but nothing real high frequency, like analog connections to the microcontroller, maybe some SMPS circuits. I was looking at some microcontroller and fpga designs that you can get kits starting at less than $100 and going up with more speed and features. Also, I see on eBay you can get some nice looking Techtronics scopes for $350 or so, 4 channel digital, etc. Just wondering if something like the AVR scope would be a useful tool or if I would be wishing I went ahead and bought a nice used scope on eBay.

RogerN

Reply to
RogerN
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But, your *digital* stuff *will* be "high frequency" (at least considerably higher than the analog examples you mentioned)

You might look into an older logic analyzer "for mostly digital circuits". Often, the cost of shipping is the biggest expense! :>

Of course, it also depends on the types of problems you are trying to troubleshoot with the device...

Reply to
D Yuniskis

"The" AVR scope? Hard to comment on it, knowing only that...

In general, though, USB-based scopes typically don't have particularly high sample rates. I'd suggest looking into one of the smaller "real" digital 'scopes, such as Instek or Rigol. There was a loooong discussion on this back in December in this group with the subject "A good digital oscilloscope?" (As you may imagine, this comes up fairly often here.)

A USB logic analyzer, on the other hand, is a useful gadget. I've been using an Intronix for years and wouldn't go anywhere without it. Overdue for a new model, though.

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Rich Webb     Norfolk, VA
Reply to
Rich Webb

I got one of the Rigol DS1052E scopes from:

Hongkong Capital International Electronics Co., Ltd.

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------------------------------------------------------------------------ Tel: 0086-755-83464576 Fax: 0086-755-83462980 Mobile phone:008613554847019 ADD:9A45 Square SaiGe HuaQiang North Rd Futian District ShenZhen China Email : snipped-for-privacy@yahoo.cn MSN: snipped-for-privacy@hotmail.com SKYPE :hkcapital.alibaba

Good price and delivery.

Works well.

I also looked at various USB scopes etc, but a stand-alone bench instrument still beats any PC based unit IMHO.

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Regards,

Adrian Jansen           adrianjansen at internode dot on dot net
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Reply to
Adrian Jansen

Go to a ham-radio swapmeet and pick up a Tektronix 465 or thereabouts. The 7000 series is dirt cheap too...but you probably have to replace a shorted tantalum cap on the plugin backplane board. EVERY dead one I've bought had this problem. Many other similar scopes are quite useful and cheap.

Bottom line, get a $20 analog scope and use it until you figger out what you really want.

Reply to
mike

Here's some of the stuff I was looking at, some stand alone, some use PC:

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But I thought this looked pretty nice:

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RogerN

Reply to
RogerN

Ugh... Spend at least over $1500. Maybe Tektronix will nail up a chief scope engineer on a cross so that you don't feel bad about spending lots of money on a scope.

Reply to
D from BC

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If you get a used logic analyzer, make sure it has the "pods". I'm simply amazed at how the box and pods get separated.

Reply to
miso

Ah, yes. And, more importantly, any *micrograbbers* that might be attached to the pods! Otherwise, you'll spend more on *those* than the logic analyzer itself! :<

Reply to
D Yuniskis

Depending on your needs, these might work:

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They're not spectacular in quality, and they're too big for the really tiny applications, but they do work, and the price is not bad.

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RoRo
Reply to
Robert Roland

I asked that question once. Turns out that anything in a big box is an instrument. The other stuff goes in the wire recycle box. By the time it gets to anybody who cares about it, it's too late.

Just look around the lab. Anything not in use has it's probes in a drawer somewhere.

Another factor is that if the recycler does know what she's doing, she knows that probes get separated. The probes are much easier to sell and bring more profit than the main box.

Bargain hunters will gladly pay $50 for a box and then another $200 on EBAY for broken probes, but they wouldn't pay $200 for the whole thing working. Simple matter of supply/demand/greed/frugality...

Reply to
mike

That looks closest to a whole oscilloscope.

Looks like an interesting toy for dedicated use. You'll be disappointed with all the hassle of trying to use it as a general purpose scope.

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This is a TOY. 1MHZ sample rate...useless...

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2465 is a VERY nice scope. Beware that they have a part that goes bad and it's made of unobtanium. Only way to get the chip is to buy another scope with a chip that hasn't failed YET. I sold mine while it was still working.

Buy one of the toy scopes above if ANY of the following are true.

1 You are an experienced measurement tech and you know every measurement you'll ever want to make and can verify that the unit can measure it.

2 You have too much free time on your hands, are tired of playing solitaire and need a better time waster.

3 You want hands-on experience with the easy part of crappy digital oscilloscope designs.

4 You want to spend more time futzing with the scope than working on the project.

Never make your first scope a KIT unless #1 applies. Never make your first scope a computer accessory unless #1 applies. Never buy a digital (or analog) scope that doesn't let you view what happens before the trigger event.

There may be exceptions, but a scope that doesn't have an input attenuator and specified input capacitance is a poor choice. Getting the signal into the acquisition unit and scaled appropriately is HARD for the novice. Last thing you need is a scope that smokes every time you touch the 12V power supply.

Don't buy a cheap scope on EBAY. Freight costs more than the scope is work, even if you do get lucky and it works. A scope that's guaranteed to work ain't gonna be cheap. Be especially wary of "can't test it, don't have time to test it, don't have equipment to test it". That's code for "broken".

I once asked about a "can't test it" scope on ebay. He accidentally replied from an email account at the world's largest used test equipment dealer. Seems that they sell the bad stuff out the back door on ebay.

If you want to make oscilloscope measurements, buy a real commercial scope. I prefer analog for a first scope.

Find a local ham and put out the word you want a scope. Most of us have more scopes than we can ever use. Maybe you can borrow one 'till you figger out what you need.

Geography matters, but put a request for a scope on Craigslist or equivalent.

You have a LOT more options if you are experienced, already have a scope you can use to fix a busted new scope etc. If you're a novice, go get a 30-40 year old analog scope CHEAP.

Reply to
mike

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Lot of good info there, thanks. I have a 10mhz leader single trace scope that worked fine last time I tried it. Do you have any recommendations on a used repairable scope? I've seen some recommend the Techtronics 465, since a lot of what I plan to use it on is digital signals/communication, I thought storage would almost be necessary.

RogerN

Reply to
RogerN

If you're interested in the information content of a data stream instead of (or in addition to) the waveform, then you'll get a lot more mileage out of a logic analyzer than a 'scope. The oscilloscope will let you check the rise/fall times, envelope, eye diagram, etc. The analyzer will let you read an I2C or CANbus conversation right off the screen without a lot of tedious bit counting.

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Rich Webb     Norfolk, VA
Reply to
Rich Webb

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Drag it out and use it. You'll quickly learn what features you need.

Do you have any recommendations on a

Already done that TEK 465, 7704 and relatives. The 7704 is handy 'cause you can get plugins for logic analysis, spectrum analysis, TDR, curve tracer etc. I've seen some recommend the Techtronics 465, since

You need to say a LOT more about what you mean by digital signals/communication. RS-232 is communication and well within the capability of your leader. Demodulating Cellphone signals is quite another matter.

An oscilloscope is a poor substitute for good design judgment. It's a time domain instrument that is very good at looking at individual transients. You want to know the risetime, amplitude and "cleanliness" of signals. An oscilloscope with a delay line will let you do that, as long as it has sufficient bandwidth for the risetimes you're observing. Two channels will let you see relationships between two signals. As long as you stay away from the maximum speed stuff will run, you'll have few problems that need high resolution timing.

Once you get beyond that, it becomes complicated real fast. Just probing the system is a nightmare. Your problem is triggering on the desired event. You quickly get into logic analyzer types of triggering and display. A two-channel scope is better than one. 4 is better, but still not too helpful if you need to trigger on 8 or 64. I once got so frustrated that I built a fixture with a PAL on it. Reprogrammed the PAL for each complex trigger and used that as one channel into a logic analyzer.

Digital storage has some benefits. Lets you see what happened to signals WAY before the trigger event. But you still have to come up with some way to trigger on the symptom.

Lets you see signals WAY to slow to be visible on an analog scope. I futzed around with a battery tab spot welder for years. About

10 minutes after I got my first digital storage scope, it was working a LOT better. I could see what was happening.

Post processing can come in handy. It's kinda nice to set a square wave to exactly 50% by punching the FFT button and nulling odd harmonics.

But digital storage has lots of issues with aliased displays, triggering, single shot sampling rate, display update rate...the list is endless. If you know what to expect, you can deal with it. But I still get confused sometimes.

What you need depends on whether you're debugging your own design. I use PIC processors for most of my hobby stuff. I don't run them faster than they're designed to go. I fix problems by inspecting the code and using "print statements". If needed, I can use a pin to generate a scope trigger exactly where I want to look. I rarely use more than two scope channels.

If you're reverse-engineering or repairing someone else's stuff, you may need a LOT more capability.

For most of my stuff, I use a TEK 308 logic analyzer. It decodes RS-232 and GPIB. It generates word triggers into a TEK TDS540 digital scope. It's OVERKILL for most things.

You can do a lot of stuff with a cheap analog scope. Complex stuff needs $60K equipment. There ain't much in between. Might as well go cheap and suffer the consequences of not being able to do some stuff. Patience pays off when you're looking for equipment. My TDS540 was free...the 308 was $5...plus about $10 in parts and a week to get it all working...but that's not the norm. Fixing undocumented stuff is not for the faint of heart.

Reply to
mike

Reply to
Nico Coesel

That depends on the depth. If you get a DSO, get one with at least 1Ms record length and peak detection otherwise you'll miss glitches.

I like the Tektronix logic analyzers for that. The trigger pattern (program is a more accurate description) can be quite complex including counters and stuff.

If the memory is deep enough you can just grab data and look through it. My logic analyzer has 4Ms per channel storage. I just trigger it on something obvious and look what is going on.

Indeed. There are many good deals on Ebay. IMHO second hand equipment from HP/Agilent or Tektronix is better than buying something new from a Chinese brand. I still need to replace my trustworthy Tek 2230 DSO but I still didn't find something that really fits the bill.

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Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
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Reply to
Nico Coesel

circuits?

was looking

starting at

see on

so, 4

scope would

nice

=A0:>

I am not sure that i would even bother with used logic analyzers,=20 USB pods are cheaper and usually fast enough (100 Mstates/s with=20 glitch capture). If your speeds are greater than that you need to=20 consider alternative data capture methods.

Reply to
JosephKK

circuits?

was looking

starting at

see on

so, 4

scope would

nice

In both cases the connector to the pod is going to kill you.

Reply to
JosephKK

I've been looking on eBay at logic analyzers, found some with pods and connectors, any recommendations?

There are HP 1630A, 1630D, 1630G, 16500 and Tektronics 1225, 1240, 1241. Seems the most that have the pods are the HP with the velcro case on top.

Or there are some USB logic analyzers that are in price range I'm looking at too.

Probably my most advanced use might be to try to figure out Allen Bradley's RIO and DH+ communication so I could program a microcontroller to operate PLC5 I/O or some kind of HMI interface. Note this is for hobby use, if I have some sucessful designs they could be profitable but I'm not counting on it.

Any recommendations on the logic analyzers I listed above? Or others to search for?

RogerN

Reply to
RogerN

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