Oscilloscopes
in [Design]
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From: RogerN on 12 Feb 2010 06:51 "Rich Webb" <bbew.ar(a)mapson.nozirev.ten> wrote in message news:8108n556skp2jcrdblfpl3eh4i8cuumil1(a)4ax.com... > 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 Thanks for the info. Myself not knowing anything about logic analyzers I'm not sure if I should get the one in your link or something like a HP 1630 for around $100 shipped. Much of what I'm interested in would be the serial protocols but more like Allen Bradley Remote I/O and DH+. I have some Allen Bradley PLC's here at home and could set up limited communication, and try to determine the commands. I think the Data Highway + and Remote I/O are electrically RS-485, there are 2 wires and a shield for connections. They only range from 57.6K baud to 230.4K baud, shouldn't require anything too high performance. Do any of the out dated logic analyzers, such as the HP 1630(A)(D)or(G), 1631 or 16500 show the data being communicated through serial, or is that more of a recent feature? RogerN
From: Rich Webb on 12 Feb 2010 10:40 On Fri, 12 Feb 2010 05:51:43 -0600, "RogerN" <regor(a)midwest.net> wrote: >Thanks for the info. Myself not knowing anything about logic analyzers I'm >not sure if I should get the one in your link or something like a HP 1630 >for around $100 shipped. Much of what I'm interested in would be the serial >protocols but more like Allen Bradley Remote I/O and DH+. I have some Allen >Bradley PLC's here at home and could set up limited communication, and try >to determine the commands. I think the Data Highway + and Remote I/O are >electrically RS-485, there are 2 wires and a shield for connections. They >only range from 57.6K baud to 230.4K baud, shouldn't require anything too >high performance. > >Do any of the out dated logic analyzers, such as the HP 1630(A)(D)or(G), >1631 or 16500 show the data being communicated through serial, or is that >more of a recent feature? BTSOOM -- They should all *show* the signals. Whether or not they have data interpreters that can be told to translate "57.6, 8-N-1, inverted" to ASCII characters is left as an exercise for the student. ;-) I haven't worked with those AB protocols but it may be that a couple of serial ports fed by two MAX488 and one MAX232A are all that's necessary. The MAX488s each have one RX and TX for 422/485 to digital, the MAX232A has two RX and TX digital to 232. Hook those up to a PC with a couple of (possibly USB) serial ports and you've got both sides of the conversation. -- Rich Webb Norfolk, VA
From: Nico Coesel on 14 Feb 2010 14:32 "JosephKK"<quiettechblue(a)yahoo.com> wrote: >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" =3D >>><miso(a)sushi.com> wrote: >>> >>>>On Feb 7, 1:57=3DA0pm, D Yuniskis <not.going.to...(a)seen.com> wrote: >>>>> RogerN wrote: >>>>> > What's the best scope to get for the money for mostly digital =3D >>>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. = >=3DA0I =3D >>>was looking >>>>> > at some microcontroller and fpga designs that you can get kits =3D >>>starting at >>>>> > less than $100 and going up with more speed and features. = >=3DA0Also, I=3D >>> see on >>>>> > eBay you can get some nice looking Techtronics scopes for $350 or = >=3D >>>so, 4 >>>>> > channel digital, etc. =3DA0Just wondering if something like the = >AVR =3D >>>scope would >>>>> > be a useful tool or if I would be wishing I went ahead and bought = >a =3D >>>nice >>>>> > used scope on eBay. >>>>> >>>>> You might look into an older logic analyzer "for mostly digital >>>>> circuits". =3DA0Often, the cost of shipping is the biggest expense! = >=3D >>>=3DA0:> >>>>> >>>>> 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,=3D20 >>>USB pods are cheaper and usually fast enough (100 Mstates/s with=3D20 >>>glitch capture). If your speeds are greater than that you need to=3D20 >>>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=20 >include pods and probes? Yes. It came with 3 16-channel probes and an extra 4M deep module. -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico(a)nctdevpuntnl (punt=.) --------------------------------------------------------------
From: JosephKK on 14 Feb 2010 19:46 On Thu, 11 Feb 2010 21:09:11 -0800, "JosephKK"<quiettechblue(a)yahoo.com> wrote: >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. After Nico's find i may have to amend that.
From: JosephKK on 14 Feb 2010 20:53
On Fri, 12 Feb 2010 05:51:43 -0600, "RogerN" <regor(a)midwest.net> wrote: > >"Rich Webb" <bbew.ar(a)mapson.nozirev.ten> wrote in message >news:8108n556skp2jcrdblfpl3eh4i8cuumil1(a)4ax.com... >> 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 > >Thanks for the info. Myself not knowing anything about logic analyzers I'm >not sure if I should get the one in your link or something like a HP 1630 >for around $100 shipped. Much of what I'm interested in would be the serial >protocols but more like Allen Bradley Remote I/O and DH+. I have some Allen >Bradley PLC's here at home and could set up limited communication, and try >to determine the commands. I think the Data Highway + and Remote I/O are >electrically RS-485, there are 2 wires and a shield for connections. They >only range from 57.6K baud to 230.4K baud, shouldn't require anything too >high performance. > >Do any of the out dated logic analyzers, such as the HP 1630(A)(D)or(G), >1631 or 16500 show the data being communicated through serial, or is that >more of a recent feature? > >RogerN > Actually that was split off and handed to a device called a protocol analyzer. It would basically leach off the serial bus 232, 422, 423, 485 or whatever and record and decode the transactions. |