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Episode 18: Siglent's SDG2042X Arbitrary Waveform Generator
June 2, 2016
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Siglent's new SDG 2042X arbitrary waveform generator is a nifty bit of gear. Here's Jack's review of it.
I'm Jack Ganssle, and welcome to the Embedded Muse video blog, which is a companion to my free Embedded Muse eNewsletter. Today we're going to do a short review of Siglent's new SDG 2042X Arbitrary Waveform Generator, or AWG for short.
But first, what is an AWG? It's basically a signal generator that can, as the name implies, generate any kind of signal, more than just a sine wave, more than a square wave, you can design your own signals that it will output. A decent arbitrary waveform generator is a pricey beast. But this unit is just $500, and that $500 buys you a lot of value. I mean, this is built like a tank. It's a metal case, it feels heavy, it feels like a piece of military equipment rather than a piece of, let's face it, Chinese test equipment.
But first, some of the features. I really like the fact that it has two outputs. See the two channels there. Sort of like that old Doublemint commercial, remember? "Two, two arbitrary wave generators in one." This particular unit goes from DC to 40 megahertz. They do have other units that will go up to 120 megahertz in the same family. One of the things that's critical is the sampling rate, because basically the way an AWG works is, there's a memory buffer, and the generator just scans values from the memory buffer and sends them out to a digital-to-analog convertor.
This thing will sample at 1.2 gigasamples per second, but only on the internal signals, the built-in waveforms. For example sine, square, pulse. If you're actually doing a real arbitrary waveform, that goes down to 75 megasamples per second. But still, that's really not bad.
The buffer is 8 megabytes, or 8 megasamples long, so you can store a pretty decent signal in there with a high precision, and what I've found kind of interesting is the signals are 16 bits, so they can get quite a bit of resolution and precision out of this baby.
So here's the signal generator. You can see there's two tabs here, one for channel one, one for channel two. The unit does have a touch screen, you can select things just by pressing on it there, pressing on it here. To tell you the truth, I find it kind of bogus. The numbers and things are so small that with my big old fat fingers I find it hard to select the thing I really want to use. I prefer to use the buttons. But some people probably would like that.
There's the main button that you would start with would be the Waveform button. This pops up the various pre-defined waveforms that are available in the signal generator, for example sine, square. When you get to square you can set the amplitude, the offset, phase, duty cycle. So as you can see you can set duty cycle, this is really more of a pulse square, but it's convenient to be able to just select it and not have to set the duty cycle. You'll notice though, as I select these different wave forms, the screen actually is updated to show what the waveform is going to look like. The pulse, this is sort of interesting, the pulse display or the pulse waveform. You can actually set the rise and fall times independently for the pulse generator, which is kind of a cool thing. The fastest it will run is 8.4 nanoseconds, which for one of these units is not bad. It's not brilliant.
Eight and a half nanoseconds is not bad for a rise time, but it's not great either, and as a matter of fact, none of my signal generators can generate an edge that is as sharp as I really need sometimes. So I went out and built this little box here which is basically a rise time improver. It sends the signal from the arbitrary wave form generator or a pulse generator or whatever, through a very high speed gate. And actually this thing has a rise time of about 700 picoseconds. And one of these days I'll do a video on this. It's a very simple device.
Now this is an arbitrary waveform generator, and indeed it will allow us to work with several different kinds of arbitrary waveforms. I can select that here. I can hit the arbitrary type here, and I have a choice of stored waveforms. These are things that you design on your PC with their so-called easy wave software. It can be any shape at all. Or there are built-in waveforms you can use. And there's a staggering number of them. For example, from the math category these are all different waveforms that the thing provides. It's way cool. I don't know what half of them are. If I pick Laplace, for example, you can see what shape will be generated. And of course we can modify all kinds of parameters like frequency and offset and all of that.
The unit does come with software for your PC with which you can design any kind of waveform that you want for the thing to output. The documentation is just abysmal. But the software is fairly decent. The version I got, the help file, was some scrambled binary thing. I don't know, I couldn't read it at all. But I was able to figure out most of the functionality of the software.
I have zoomed out a bit so that you can see the output of the waveform generator on my oscilloscope. For this experiment I'm just running channel one, it's the only one that's turned on. Channel two is turned off. And you can see there's a sine wave on channel one. It does support sweep and burst modes. So for example, here's a sweeping mode and you can set sweep frequency, range, and all parameters that you would expect.
Burst mode allows you to select all kinds of parameters. Here I've told it to output just one cycle of a waveform. I can change that to some other number cycles, it's not here, well you can see it's not triggering well. A different number of cycles are being generated. And again, all that stuff is configurable.
I'll go ahead and turn channel two on. They're both generating sine waves of the same frequency. What's very cool is that you can actually couple the channels together. I'll turn coupling on, and now channel two, it is sweeping at twice the frequency of channel one, or three times the frequency, or any other multiple that you want. The resolution is incredible. This is down to one part in a million is available. Or how about this? We can couple based on phase. So as I spin the big knob, you can see the blue trace, the phase is slowly shifting to the left as we change the relationship of the two sine waves.
On eBay, you'll find there are an awful lot of really inexpensive signal generators and AWGs available. I mean, sometimes on the order of $50. And I have reviewed some, and I've got a bunch more stacked up here I've gotta review one of these days. They're not bad. But look at the specs. They are nothing comparable to the Siglent. Their rise times are terrible, their sample rates are usually very, very low. But they're great for some applications. This unit is a pro unit. This is something that you'd use in a real electronics lab. And I have to say, I highly recommend it.
So, there you have it - a summary of the Siglent's new Arbitrary Waveform Generator. Thanks for watching, and please stay tuned to ganssle.com for more videos and over a thousand articles about better ways of building embedded systems.