Monday 10 April 2017

R&S Give Away

Count me in for the Rohde and Schwarz RTB2000 Oscilloscope giveaway! And here is why!

MJLorton is giving away a RTB2000 oscilloscope on his channel so in part this post is in response to that but also this post is a bit of a whinge about Keysight.

MSOX2000 Gripes

I have a beautiful MSOX2024 that I've had for two years or so. I bought it as a re-furb unit and added a couple of options (expanded memory, I2C/SPI decoding). It has super fast waveform update rate, its really nicely built and pretty easy to use.

There are a few things I really wish the scope did:


  • Segmented memory (history R&S call it) so I can capture multiple serial or analog events over time and see each one.
  • General serial decoding. When I was working on my power supply project I could have really used this to decode serial problems caused by dodgy soldering of fine pitch chips!
  • Decoding of serial signals on the digital ports. I don't get why this limitation exists and this is pretty annoying.
  • LAN interface so I can automate some measurements.
So the first two things are additional software options I don't currently own. The list price segmented memory is $AUD450 and RS232 is $AUD737. That's nearly half what I paid for the scope!

There is an 'Application bundle' that includes everything for $AUD1820 but there is no discount for the options I already purchased.

No serial decoding on the analog channels is a real PITA. The problem is if you are trying to decode a bidirectional SPI signal you have used up all your channels and can't look at anything else. At this point you may as well be using a cheap USB logic analyzer as your correlation with analog has gone out the window. You can cheat to some extent and use clock-timeout instead of a dedicated CS line but in my case there were multiple SPI devices on the bus so that wasn't going to work either.

The digital probes also make much more sense for this type of work as they are fine and better suited to attaching to a wedge or the legs of  chips etc.

The only way to get serial decoding on digital channels is to upgrade to a MSOX3000. The cheapest one I would consider is a MSOX3014 and these start at $AUD10K. I found a re-furb with no probes for the bargain price of $AUD6500. They are a very nice piece of kit but this is well out of hobby territory. The application bundle is an eye-watering $AUD4500 (but it does include a lot of stuff).

The cost of the LAN card for these scopes is insane - $AUD400. Ok it has a VGA adaptor too but I didn't actually want that. I managed to work around this as many people have reverse engineered the LAN interface and provided PCBs. I got a PCB, assembled it and got around the problem.

While on this topic there is a rich thread over at the EEVBlog forum on how to hack this scope (via the LAN interface) to enable all the software options. Based on the prices above you can see why!

R&S RTB2000

I've been watching a number of reviews of this scope by MJLorton, Dave Jones at EEVBlog and Mike's Electric Stuff.

What most impressed me was:
  • The big, clean hi-res interface. I love the numbers on the graticule!
  • 10 bit converter and therefore the nuts low signal performance. I've been using my old analog scope for this as the lowest I can go with the MSOX2000 (and a x10 probe) is 10mV per division.
  • 16 digital channels, multiple serial decodes on digital or analog channels.
  • 'History' (segmented memory)
  • LAN!
The cost is still steep but element14 are offering the fully-loaded model for $5AUDK which is comparable with the MSOX2024 with no software options.

Active probe interface would have been nice. Not for hig-speed differential but for current probes or high-voltage differential probes etc. It would also be nice if the scope makers got together and standardized this! FFS!

Conclusion

Maybe I will get lucky and MJLorton will post me a scope but in all likelihood I'll be waiting for another second hand unit to come by.

I get that a lot of engineering goes into these units and they need to earn a crust but I still find their pricing structure steep.

Some of these options aren't really options though - are you going to buy a scope with 100K points of memory per channel? No LAN interface? I wouldn't (not again anyway) so really listing the memory upgrade etc separately is just a way of hiding the real scope price. Serial decoding is another example.

Surely there is some value in putting their kit in the hands of home-gamers like me (as AvE calls us) as one day we might buy a lab full of their gear (most hobby electronics people are students but some might be one-man shops that eventually go-big with a product). They don't though - they assume we are going to spend as much as a university and so instead we go buy Rigol or Siglent and make do.

Maybe the 2000 wasn't the right purchase for me.

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