A scope to fulfill

Started 1May2015. Updated 12Dec2015

Intro

For a small private project I have tried the best of the scrapped scopes I brought home from work, but the 1997 model Fluke PM3380A didn’t pass its own diagnose procedure. The amplitude of channel 1 changed when I pushed the curve up. And the old Philips GM 5650/02 from around 1955-60 that was ditched from work 20 years ago (after 20+ years of shelf life) was completely out of scope, as now being a conversation piece only (the handbook with circuit diagram is a gem in itself. Hand drawn diagram!-) So, why not also make the path a goal and take the opportunity to learn about USB based oscilloscopes (or, I have learned by investigating for this note: networked oscilloscope?) that have their client SW on a PC/Mac/Linux/etc.? Then find one to buy so that I also can recycle the scrapped scope and store the extra table away. Sad and not.

But there’s more to it. Along the emotional path, this is a note in the A model to fulfill line of notes [1]. It’s got to do with more than just selecting an oscilloscope. Because, when I was a youth I built one that worked, and one that never was finished. Some stuff remain, like the 2AP1 CRT [2], and a picture of the scopes I built [3] (which also has the circuit diagram with 3 tubes). They are since long gone now, but the cathode ray tube still casts a warm shadow on me:

2AP1 CRT (Cathode Ray Tube)

Disclaimers

  1. This note is not meant to be a neutral or objective review, but I do try to be accurate. Should there be any obvious errors or omissions, please comment below or mail me
  2. Even if I discuss products here, I don’t have any deal with any manufacturer. There’s no “courtesy of” free HW and no money involved. And no ads here. I am 100% independent
  3. The external pictures used I have not asked for permission to use, but since they are used in a product discussion I reckon it’s ok
  4. I am no oscilloscope specialist!

But I need it at home!

Oscilloscope screens

Above are a couple of oscilloscope pictures I measured on my private aquarium control XMOS project [4]. I brought the set-up in a card box to work. The left screen-save is the I2C connection that remarkably enough works with my Adafruit display (even if I would like to add a pull-up). The right is the analogue to digital (ADC) conversion on the XMOS startKIT that works so and so at the moment. The scope at work is a Keysight Technologies (former Agilent, but Hewlett Packard or HP when Steve Jobs and I were young) model InfiniiVision 350 MHz scope that was bundled with an even larger scope (see [5]). When I saw what I saw I decided that after 50 years I again need a scope at home.

USB scopes

Not an oscilloscope instrument (with screen and buttons and an always annoying fan, no matter how new and fancy it is!) I thought, but a USB (or.. networked?) scope. A table top instrument with screen and buttons would be “too much office” and too little to do with. I have decided to bet the two above against each other: PicoScope 3203D MSO from Pico Technology and the BitScope 10 from BitScope. (And now SmartScope from LabNation). Yes, the first is 19 cm wide (and about 4 cm high), and the latter 6.5 cm wide (and about 2 cm high). So the scale in the figure should be ok. But at what level do they compare? Remember I wasn’t only interested in the technical specs, but trying to match them with my assumed expectations. Or use the case to find my expectations.

Another matter. If I come to work a morning and have forgotten to switch off the modern fanciful scope the day before, I hear the sound of the fan – and it’s already warm in the office. (An office in this case is a room, not a desk among desks.) The scope needs that fan for a good reason (one of them being that it got hot in my office). But still, at home, (when) do I need a fan-full scope?

In the table below I will try to compare and find out what’s in them for me. MSO stands for Mixed Signal Oscilloscope (see Wiki-refs below). Both are MSOs:

PicoScope 3203D MSO

BitScope 10 (BS10)

Official source at PicoTech: 3000-series (spec) Official source at BitScope: BS10 (And a presentation here)
Alternative: none, since I want the cheapest with MSO Alternatives; the larger networked BS325 or BS445 (oldish, see future, where Raspberry Pi seems to take over the networked segment. Personally I’d want to buy a ready and boxed solution, if I were to). A networked client may also run on touch tablets and phones. An alternative may also be the smaller USB scope BS05.
 Not isolated (floating or galvanically isolated). BS10 is not isolated (not floating or galvanically isolated). But the networked scopes are. Or could one use a USB isolator like the USB2ISO USB 2.0 isolato? (I have one for my stereo to remove hum). But then, a differential probe certainly helps in many cases, since instead of raising a floating zero level, there are proper measurement points for it, see DP01.
It would probably do “everything” for me. One analogue channel and it samples at 1 GS/s., half for two. Repetitive signals up to 2.5 GS/s. It has USB 3.0 to support it, and a large frame buffer in the box. I am not certain whether 20 MHz analogue sampling will be enough for me. A µs pulse would be seen by 20 samples, 100 ns would have two samples (Nyquist?) and 10 ns wouldn’t be seen if it comes alone. But if the pulse were repeating a 10 ns would be seen by 50 samplings (repetitive under-sampling of 500 MS/s).  It can do with USB 2.0, so I assume I’d have to wait longer after triggering.
The whole package would cost more than the double of BS10, but then it’s available from a Norwegian site, with our 5 years guarantee, I’d assume. I’ll have to add a BitScope Micro Oscilloscope Probe Adapter (“Hammerhead”), needed for standard oscilloscope BNC-type probes (++). One year guarantee, free repair. See picture above.
Too large on my desk? It’s so small! But the adaptor fills in some of the gap.
Their perspective seems to be professionals. Solid. But to be honest my last HW design was in the nineties with a TMS320 signal processor and some PALs. After that I’ve done embedded SW only. Perspective is Raspberry pi angle, with lots of blog posts. Modern. They have a Network server and a Trello BitScope support board.
It generates “everything”. It’s an analogue waveform and voltage generator. It also does logic and clock generation.
The client SW is a only beta for Mac OS X (1Q 2015), requiring the Mono MRE (Microsoft’s .NET Framework based on the ECMA standards for C# and the Common Language Runtime). Windows, several Linuxs and Mac OS X. A USB driver for OS X must be installed. But is Mac low priority (here)?
Somewhat aside: the iCircuit app that runs on OS X, iOS, Windows 8, Windows Phone and Android has been developed by Frank Krueger in C# on MonoTouch by Xamarin. iCircuit also has an “oscilloscope” simulator output. I did buy iCircuit for OS X. Is this close to PicoScope’s development path? (I remember I did SPICE answers on an exam in 1983. It was then already 12 years old and quite much in use at NTH)
PicoScope Software Development Kit (SDK) allows me to write my own software and includes drivers for Microsoft Windows, Apple Mac (OS X) and Linux (including Raspberry Pi and Beaglebone). So the USB box may be controlled from Microsoft Excel, National Instruments LabVIEW and MathWorks MATLAB and of course C, C++, C#, Visual Basic on the .NET platform. (And maybe Objective C (but not Swift) which seems to come on .NET now [6]). BitScope Library API is for Window, Linux, Mac OS X and ARM platforms including Raspberry Pi. C 2, C++ 3, Python 4 and Pascal 5. The Library provides full programmed access to the BitScope Capture Engine which then builds scripts with atomic instructions for the BitScope Virtual Machine (i.e. a standardised command set: good – until you need to expand it? But they say it’s unchanged since the start). I have not been able to find the spec of the VM on an open site, but there’s some on the presentation, first row in this table.
Capturing a single deviation from a repetitive curve, “mask limit testing” is able to pick out an odd curve in series of normal curves (analogue). Capturing a single deviation from repetitive a curve. I think this is “framed” or “continuos” in this universe (analogue)? Is this the same as “segmented memory” as mentioned in other scope literature?
Need to find out. Roll mode? BitScope support tell me to follow this board for a future Streaming mode. More in note 101
Same as ->? VISA (Virtual Instrument Software Architecture) interface? I don’t think directly?
TODO?  [6] also shows that Visual Studio Code now is downloadable to run on OS, but it’s only the Code version for web and cloud applications. TODO? Porting the BitScope CaptureEngine (or use the VM directly?) onto the XMOS xCORE-USB Core Board (with sliceKIT-USB Kit) – or some other board  with the extra needed user available USB connection (or an XS1-U processor)? To use the BitsScope HW as a complex data I/O unit? Remember the XMOS “extension to C” (also called xC). It runs safe CSP in C disguise with channels and task interfaces more like Ada. And it’s got guaranteed deterministic timing at 100 ns granularity, where the tool gives an error message if the timing requirement isn’t fulfilled. What can BitScope (users) do with that? Depending on how large the BitScope clients are I doubt putting all onto the XMOS(?) Even with 8(+) cores XMOS processors are rather “small”. The “smallness” comes from the fact that the resources are handled by a built-in scheduler to make guarantees possible. This allows only for so and so many channel ends. etc..
Software and updates are free. From their page: advanced display, math channels and filters, custom probes in PicoScope oscilloscope software, high-speed data acquisition and digitizing and powerful tools provide endless options. Included and forever free updates is the DSO software: digital oscilloscope, mixed signal scope, waveform generator, spectrum analyzer, logic analyzer and data recorder.
PicoTech looks serious. The audience is probably more professional. It’s based in the U.K. BitScope looks serious. It’s not “a toy”, but has its audience. It’s based in Australia.
First USB product in 1991. It seems to have started in 2001 (but what’s this from 1998?)

I have added points in the table after I received the BitScope 10 that I ended up buying.

LabNation SmartScope

This has been a Kickstarter project with result turning up in the autumn of 2015 (at least that’s when I discovered it). Their page is at https://www.lab-nation.com/. The company is based in Antwerp, Belgium. SmartScope is an

  • oscilloscope with two channels and 30 MHz -3dB point at max 40V @ 100 MS/s each with a buffer of 4 million samples per channel;
  • logic analyzer with 8 channels @ 100 MS/s each;
  • wave generator with one analogue and four digital outputs at 2048 samples for each;
  • an it can export waveforms in Matlab (.mat) or Excel (.csv);
  • the client runs on all platforms: Windows, OS X, Linux, Android, iOS (jailbroken, which means not available to me!)

Hmm.. Very interesting, indeed. But alas too late for me – I have my BitScope BS10.

Velleman, DSO Quad and Uni-T UT81B

These are USB scopes that I have added here to make the list more complete. The first I found in the catalogue from Kjell & Company and all of three brands were reviewed in IEEE Spectrum (here: old from 2012). Velleman also has a wifi-oscilloscope. No further comment, except again: I dont’ have any ads here, don’t get paid by anyone, neither by money, gift nor any other means. I just love to write, find out things and tell about it.

Postscript

When I saw that the table above got more and more biased to the BitScope side I thought it was time for action. I will do some hobby-type electronics when I get more time for this at home. I will buy most cards ready-made and will basically do some simple interface stuff. I will not try to repair the old Fluke. Still a Megger won’t do. I am certain that PicoScope would also have been a good choice. But I think that double price, double real estate on my desk, perhaps double functonality (and usability) and not-so Mac OS X ‘ish is not for me now. But I’ll keep you posted. Maybe I’ll make a “My BitScope notes” to follow up on the (still in work) My XMOS notes? I did.

A memorandum

Around 1982-84 I was on a team developing the first microprocessor-based addressable fire detection system. In the world, actually. Autronica BS-30 (BS30). We were using an 8035 controller (8048, but with external memory) and developed on an Intel “blue box” Microprocessor Development System. The Intel MDS had external trigger inputs.

I remember I wrote a task scheduler for the front panel. I also did the HW for it. It contained display, LEDs, printer and keys and was the master communication unit talking with up to eight smoke detector loop controller units.

The smoke detectors communicated by drawing a certain amount of current for so long, and after this we stepped the address up by pulling the line low from the controller for some time. This was the counting pulse; we also had a longer reset pulse. It was (is) a two-wire loop, so the signal couldn’t be low for too long.

At one occasion I couldn’t understand what had happened. There was something on the loop that I needed to find out of. I could see a blip on the scope, but then it was gone.

However, we had just got a new scope, a “storage scope” where we could control the afterglow on the screen. It was quite nice.

I wondered that if I could see the blip with my eyes, maybe I could make a probe to pick it up? It was actually at the same place on the screen every time.

So I took a plastic pencil and inserted a phototransistor and made some interface electronics, and connected it to the MDS’s trigger input. I held the pencil up where the curve should appear – and it triggered!

The MDS stopped at the instruction! (The processor wasn’t that fast!) At that time I could even inspect the call tree proper. It didn’t take too long to find the error. Even with only a command language interface, no windowing system, “just” the ISIS-II operating system.

This fire detection system ran for some years, even at a nuclear power station before it was replaced by a newer system, also from Autronica

I think this functionality is in the PicoScope’s mask limit and BitScope’s framed trigging (above). It’s even possible in 2015!

References

Wiki-refs: Communicating Sequential Processes (CSP), ISIS-II oeparting systemMixed Signal Oscilloscope (MSO), Mono, NTH/NTNUProgrammable Array Logic (PAL), SPICE, VISA interface

  1. A model to fulfill, blog note by me, see http://www.teigfam.net/oyvind/blog/001/index.html
  2. 2AP1 Cathode Ray Tube (from 1944?, which I bought from “Surplus radio” in Oslo around 1963. See data sheet at http://www.r-type.org/exhib/aaa1012.htm and quite some great stuff at YouTube, like https://www.youtube.com/watch?v=3kn1RAhKp4Y
  3. My DIY electronics in the sixties: http://www.teigfam.net/oyvind/home/technology/076-radiobyggboken/#oscilloskop
  4. My XMOS notes, see http://www.teigfam.net/oyvind/home/technology/098-my-xmos-notes/, used to develop my aquarium controller project
  5. Keysight Technologies oscilloscope model InfiniiVision 300 X-series DSO-X 3034A, 350 MHz, 4 channels..http://literature.cdn.keysight.com/litweb/pdf/5990-6619EN.pdf
  6. Microsoft hopes to court iOS apps to Windows 10 with Objective-C support, and  “Visual Studio Code is now available to download for OS X, allowing code to be written in .NET, JavaScript, and a number of other frameworks and languages”, (only the Code version for web and cloud applications), see http://appleinsider.com/articles/15/04/29/microsoft-hopes-to-court-ios-apps-to-windows-10-with-objective-c-support
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