Oscilloscopes
in [Design]
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From: Rich Webb on 11 Feb 2010 08:23 On Thu, 11 Feb 2010 05:29:50 -0600, "RogerN" <regor(a)midwest.net> wrote: > >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. As mentioned up above, I use http://www.pctestinstruments.com/. Your mileage may vary. Some things to consider: 1. The USB logic analyzers tend to split into two groups based on their capture mode. There is a group with deep sample memory that always captures in real time. This leads to a trade-off between duration and precision, where sampling at 100 MHz into a 1 Mb buffer fills the buffer in only 10 msec. The other class has shallower buffers (typically a few Kb) but can tag each sample with a timestamp, so sampling at 100 MHz is still possible throughout an event that lasts several seconds. On the other hand, if there's a channel with a lot of activity then the buffer will be filled correspondingly quickly. 2. Pay attention to the maximum input voltage range and also to the trigger range. There are some inexpensive USB LAs that have a fixed front-end range of 0-5 VDC and a fixed trigger threshold but ones that handle at least +/- 20 VDC with adjustable triggers aren't much more expensive. 3. Back in the day, one feature of LAs was the ability to load a machine language interpreter and, with the proper assignment of channels to address, data, and control busses, to trace program execution and trigger on events like the change of a memory location. Nowadays, at least in microcontroller land, not so much. Instead, look for the ability to interpret common serial protocols like CANbus, I2C, etc. -- Rich Webb Norfolk, VA
From: Nico Coesel on 11 Feb 2010 13:01 "JosephKK"<quiettechblue(a)yahoo.com> wrote: >On Sun, 7 Feb 2010 23:24:33 -0800 (PST), "miso(a)sushi.com" = ><miso(a)sushi.com> wrote: > >>On Feb 7, 1:57=A0pm, D Yuniskis <not.going.to...(a)seen.com> wrote: >>> RogerN wrote: >>> > 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 >>> >>> But, your *digital* stuff *will* be "high frequency" (at least >>> considerably higher than the analog examples you mentioned) >>> >>> > connections to the microcontroller, maybe some SMPS circuits. =A0I = >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. =A0Also, I= > see on >>> > eBay you can get some nice looking Techtronics scopes for $350 or = >so, 4 >>> > channel digital, etc. =A0Just 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. >>> >>> You might look into an older logic analyzer "for mostly digital >>> circuits". =A0Often, the cost of shipping is the biggest expense! = >=A0:> >>> >>> Of course, it also depends on the types of problems you are >>> trying to troubleshoot with the device... >> >>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. > >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. I recently purchased a used logic analyzer from Tek for $450. I looked at the USB LAs as well but if you want something nice (lot of depth, at least 1Gs/s, versatile triggering and input specifications specified at the tip of the probe) you'll pay a lot more. -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico(a)nctdevpuntnl (punt=.) --------------------------------------------------------------
From: Nico Coesel on 11 Feb 2010 13:05 "RogerN" <regor(a)midwest.net> wrote: > >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. A TLA704 can be bought cheap if you have some patience. This runs plain Windows98 (or Windows2000 if you upgrade the memory) instead of some archaic Unix. -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico(a)nctdevpuntnl (punt=.) --------------------------------------------------------------
From: JosephKK on 12 Feb 2010 00:05 On Thu, 11 Feb 2010 18:01:22 GMT, nico(a)puntnl.niks (Nico Coesel) wrote: >"JosephKK"<quiettechblue(a)yahoo.com> wrote: > >>On Sun, 7 Feb 2010 23:24:33 -0800 (PST), "miso(a)sushi.com" = >><miso(a)sushi.com> wrote: >> >>>On Feb 7, 1:57=A0pm, D Yuniskis <not.going.to...(a)seen.com> wrote: >>>> RogerN wrote: >>>> > 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 >>>> >>>> But, your *digital* stuff *will* be "high frequency" (at least >>>> considerably higher than the analog examples you mentioned) >>>> >>>> > connections to the microcontroller, maybe some SMPS circuits. =A0I = >>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. =A0Also, I= >> see on >>>> > eBay you can get some nice looking Techtronics scopes for $350 or = >>so, 4 >>>> > channel digital, etc. =A0Just 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. >>>> >>>> You might look into an older logic analyzer "for mostly digital >>>> circuits". =A0Often, the cost of shipping is the biggest expense! = >>=A0:> >>>> >>>> Of course, it also depends on the types of problems you are >>>> trying to troubleshoot with the device... >>> >>>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. >> >>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. > >I recently purchased a used logic analyzer from Tek for $450. I looked >at the USB LAs as well but if you want something nice (lot of depth, >at least 1Gs/s, versatile triggering and input specifications >specified at the tip of the probe) you'll pay a lot more. At that speed the choices are get good stuff or go without. Did that price include pods and probes?
From: JosephKK on 12 Feb 2010 00:09
On Sun, 07 Feb 2010 17:29:36 -0500, Rich Webb <bbew.ar(a)mapson.nozirev.ten> wrote: >On Sun, 7 Feb 2010 15:31:46 -0600, "RogerN" <regor(a)midwest.net> wrote: > >> >>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. > >"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. http://www.pctestinstruments.com/ That is pretty good for an LA at that price. |