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Tek spins scope-like 3-in-1 function generators

Posted: 29 Aug 2005 ?? ?Print Version ?Bookmark and Share

Keywords:Tektronix? tds1000? tds2000? tds3000b? oscilloscopes?

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When I sat down recently with Tektronix Inc.'s field marketing director to get a hands-on demo of these new arbitrary/function generators, I felt like I was re-visiting the rollout of Tektronix's TDS1000, TDS2000 and TDS3000B series oscilloscopes. I had to look closely to be sure I wasn't about to test drive a scope. The new afg3000 series have big (5.6-inch) menu-display LCDs that look very much like oscilloscope screens.

"Yup, " confirmed Gary McFarlane, "they have the same look-and-feel. The settings are shown on-screen, and the function and mode you select is displayed as a waveshape, too. You can also quickly see the scale you're on, and select frequency, period and phase using soft keys. "

It's worth pointing out the generators' very large color LCDs, too. Competing models from companies such as Agilent and Fluke have much smaller LCDs. The competition also has more limited color.

Stack 'em high
Adding to the oscilloscope illusion, when McFarlane operated the AFG3102 in our demo session, he stacked it with one of Tek's TDS2024 4-channel oscilloscopes. This clean looking high-rise package was really compactand didn't gobble much benchtop real estate, either. Very nice.

One of the things not mentioned in Tek's press release is where these new generators stand versus their competition and like pieces of test equipment. As McFarlane points out, there are quite a few low cost arbitrary waveform generators, or ARBs, out there, but most typically top out at 50MHz or perhaps 80MHz at best.

"If you need to generate signals at 100MHz," said McFarlane, "generally you have to purchase an ARB with much more capability. You might have to spring for an expensive box that goes to 500MHz."

Six models
You won't be saddled with that problem with these new boxes. With six models in the AFG3000 series line, you can get ones with 240MHz function generator capability and 2GS/s speeds, or slower ones at 25MHz and 250MS/s rates. That should let you select a model to closelyand cost-effectivelymeet your needs.

Single- and dual-channel models are also part of the family mix. By the way, the slash character in the Arbitrary/Function Generator moniker underscores the ability to deliver both arbitrary waveforms and math-based functions such as sine and pulse waves.

At the low end, a Model AFG3021, priced at about $1,780, generates sine waves at up to 25MHz, and works as a pulse/ARB to 12.5MHz. It operates at the arbitrary waveform sample rate of 250MS/s. Arbitrary waveform memory supports four waveforms, of 64KB each.

At the top of the line is the $8500 dual-channel AFG3252, with 240MHz sinewave capacity and a 120MHz pulse/ARB capability. It packs a waveform sample rate of up to 2Gbps, and has memory enough for four waveforms of 128KB each. In between are other models at 100MHz with 1GS/s sampling rates.

Any of these is capable of generating waveforms that you define, as well as standard ramp, triangle and sinewave signals. All deliver 14 bits of vertical resolution. The pulse generator function delivers streams of squarewaves or pulses, with settable and separate rise and fall times. "The ability to set rise and fall time has been unavailable in this price range prior to this product line," McFarlane pointed out.

Wide appeal
It's likely that the models at the top of the series will appeal to those of you developing high-performance computing, communications and video designs. The more basic models would make cost-effective tools for labs in schools, and will also appeal to designers of consumer electronics, medical and automotive systems, where higher frequency gear simply isn't needed, but performance and cost are nonetheless important.

Prices for other models range from $2,700 for a dual-channel 25MHz Model AFG3022, to $3,600 for a single-channel AFG3101 100MHz unit. An AFG3102 dual-channel 100MHz box comes in at about $4,800. Just below the dual-channel AFG3252 is the single-channel equivalent, the AFG3251. It's priced at $6,400.

Independent selection
Not also stated in the press release is that the three dual-channel models provide completely independent selection of waveform and frequency for each channel. If you're working with mixed-signal devices, for example, you'll be able to drive a device with both analog and digital signals simultaneouslyand at two distinct frequencies if necessary.

Similarly, two serial bit streams, one ideal and the other impaired, can be fed to a component at the same time. By using the generator's phase-align and phase-adjust features, the dual-channel versions can also generate I/Q channels (in-phase and quadrature) for testing communications circuits.

You can also generate AM, FM and PM signals, as well as noise and DC. Internal modulation can be set from as low as 2mHz to as high as 50KHz. You can set AM modulation from zero all the way up to an over-modulated 120 percent, and also set FM deviation. PM phase deviation can be varied from zero to 180.

Remote control
Finally, these instruments can be operated on a local area network (LAN), or using IEEE-488/ general-purpose interface bus (GPIB), or across a USB connection. All of these ports are accessible from both front and rear panel jacks, too. There's also a USB port for a memory stick. It lets you store and load waveforms. That can be very useful where multiple users are sharing generators.

If you'd like an arbitrary/function generator that's user-friendly, I think you'd be hard pressed to find a family that has models that top Tek's. The AFG3000s will save you from obsessively looking at your generated signals with a scope to make sure they're right, which can save time and might free up a probe at times. That big display also inspires confidence, as it reveals a lot about the generator's signals and configuration.

When you factor-in Tek's ArbExpress 2.0 software, and the way it translates scope data from all of the company's oscilloscopes (and lets you transfer waveform data out of MatLab), these instruments shape up as friendly, powerful and cost-effective.

- Alex Mendelsohn

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