Episode 20: Review of Siglent's SDS1204X-E Scope

January 18, 2018

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Video Transcription

Hi, I'm Jack Ganssle and welcome to my Embedded Muse video blog, which is a companion to my free embedded newsletter which is sent out twice a month. Today I'll review the new Siglent SDS1204X-E Digital Oscilloscope. And I will be giving this away at the end of this month (January 2018). At the end of the video, I'll tell you how you can enter the contest to win this thing.

This is the first of a new line of Oscilloscopes from the Siglent. And this particular model is a 200 megahertz job with four vertical channels. It retails for about $750 but lower level models, 100 megahertz with two channels, are available for as little as $350.

Back around 1972 or so I convinced my boss the buy a fancy Tektronix high-performance Oscilloscope. We paid, as I recall, about $20,000 for it, which in today's money is something like $100,000 and it had about the same performance as this model, which is just a tiny fraction of the price.

As you can see this model has four channels with a one GS/s acquisition rate. Seems kind of weird for a 200 megahertz scope to have such a high rate, but they do offer an option for adding 16 digital channels. At this moment, I can't find that option on the website so I don't know what it costs.

The screen is 7 inches and 800 by 480 pixels, the writing is small. You can see it's tiny in there but it's very crisp and very readable.

In the olden days scopes were so heavy that they didn't move while attaching a probe. This one weighs 2.5 kilogram so you can see it moves away from you when you try to put a probe into the thing. One nifty thing about the Siglent is that they have these nice hand holds here so that you can grab onto it while you do insert a probe.

Though there are four channels, you can see each of the channel inputs are here, there's only one set of vertical controls. I was originally put off by one of the early Rigols because it had the same sort of thing. The way it works is that there are four buttons here to select which channel these buttons deal with. So I can go to channel two, I've turned it on and I can set the gain for channel two, I can go back to channel one, set the gain for channel one. And to tell you the truth, I'm not a big fan of that.

I like having a separate control for each channel but it's not as bad as I thought it would be, to tell you the truth. You just have to get used to it and you can see on the display here it shows which channel is turned on and what the various settings are for that channel. It's an okay arrangement but I do find myself sometimes accidentally switching the horizontal control when I'm trying to go for a second vertical channel.

Now, this may be difficult to read because the characters on the display are very small but you can see it. The sample rate here is 500 mega samples per second. I said there's a one GS/s scope in this. However, the way it works is there are two analog to digital converters in here. One is used by channels one and two, the other by three and four. So here are channels one and two turned on and that drops the acquisition rate down to 500 mega samples per second.

If I turn off channel two, it goes back up to one GS/s. I can turn on channel one and channel three and it stays at one GS/s because they're using each of those two A to Ds.

The scope will capture 400,000 waveforms per second. It has a 14 mega-point memory.

One feature of any decent scope is its zoom feature. I press in the horizontal control and you can see the display kind of grays out there. That little ungrayed out part there is then blown up on the bottom here. So you can see the sine wave in great detail there. It can open up, zoom out you see more of the sine wave. I wouldn't buy a scope without that feature.

The scope includes a segmented memory which is a very cool feature. I don't use it very often but when I do it's a lifesaver. Basically, you can divide the memory up into a number of different chunks, segments, and you can tell it to trigger when an event comes along, fill that chunk and then stop acquiring data until that trigger signal comes along again and then it will start to record data again. So what this means is that you can have something that happens infrequently. An infrequent trigger event and have a very high sweep rate. When that event occurs, it fills the first chunk and then it stops acquisition. When that trigger occurs again maybe millisecond, seconds, hours later, it then acquires another chunk. Maybe at a very high acquisition rate. With this scope, you can divide memory up in into 80,000 separate chunks. So here's how you use the segmented memory.

Here's a pulse, is about 20 nanosecond pulse and it's coming only about 10 times per second. I've got the sweep rate cranked up pretty high here at 20 ns per division, clearly, the memory would fill after one of these pulses came along. You wouldn't be able to see any of the other pulses. So I can go into the acquisition menu, turn on the sequencing and I've set it to break memory up into 30 individual chunks. I'll turn on segmented memory, and now what's happening is it's acquiring this pulse into 30 different chunks of memory, and if I stop the acquisition, I can press the history button and turn on what's a called the list and here you can see all the different acquisitions, characteristics of each of the acquisitions then I'm scrolling through with the universal button. And as I scroll through each of these chunks, you can see a different one of those acquired chunks is displayed.

The scope will also trigger on things like I2C, SPI, LIN, CAN, all those serial buses. So you can actually trigger on a particular event happening or you can just acquire data on those serial buses and a scope will decode the data. In episode eight of the series of videos, I talked about how a 2 GPIO bits you can actually send all kinds of cool debugging information out of your embedded system. It's sort of like a printf to the oscilloscope. And a scope like this is perfect for that kind of application.

There are a ton of other features. One of the more interesting ones is if you have a Siglent arbitrary waveform generator the scope can control it. So it's sort of like a spectrum analyzer with a tracking generator. In other words, the scope can sweep the arbitrary waveform generator and then take the data coming in from whatever circuit you're actually analyzing.

And what this means is that you can create Bode plots and rather like a spectrum analyzer would. Now, it only has a analyzer 200 megahertz bandwidth who has a real spectrum analyzer would be typically many gigahertz. So it's limited but it can be a useful feature if you're trying to characterize, for example, filters and circuits of that like.

I think the scope offers a lot of value for the money. It's like so many other entries into this market today. Rigol for example, Siglent like this scope, even Tektronix now offer some very inexpensive and decent quality scopes out there.

This is truly a golden age for test equipment. You can get a lot of capability for a very reasonable price.

So that's it. If you'd like to win the scope, go to ganssle.com and there's a contest entry there. At the end of January 2018, I'll be awarding this to one lucky winner. Thanks for watching and don't forget to go to ganssle.com for thousands of articles about embedded systems and many more videos.

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