A working engineer posted this question, which appeared in my LinkedIn status stream earlier this year:
“I want to set up a home electronics test bench for maker projects. I would like a scope (perhaps with logic analyzer), waveform gen, power supply, volt/amp meter. My interests are high fidelity audio, and Arduino/RPi type projects. I am seeking recommendations on setups that won’t break the bank. This is for my own personal use, not work work.”
Now I style myself as someone who is familiar with this topic. In fact, it’s near and dear to my heart. I’ve had a home electronics lab since attending high school, and that’s more than half a century of home labs. My basement lab in high school had a Heathkit IO-18 tube ‘scope that I built myself. The lab in my dorm room at college had a transistorized Heathkit IO-104 ‘scope that I built after the tube ‘scope. I fitted a lab into the walk-in closet of my first 2-bedroom apartment when I joined HP. I brought the second Heathkit ‘scope along. I set up labs in my first, second, and third homes. I designed an entire lab and workshop room into my current house.
So here’s my initial reply to the question posted on LinkedIn:
“With one exception, I like test equipment with knobs. That refers to scopes, signal sources, and power supplies. Siglent makes a nice, economical line of these kinds of instruments and they’re all available tomorrow via Amazon. You will probably need multiple power supplies, and you’ll want an old-school linear supply for audio work. Once upon a time, I’d have said buy only HP T&M gear (because I worked there, so I have a preference), and older HP gear from eBay can be nice, but the Siglent stuff comes with a warranty.”
“For a good handheld meter, I’d always pick a Fluke. I’ve had a Fluke 77 for four decades and still use it. It’s built like a tank. If you think you need more resolution, consider a good, refurbed HP 3478.”
“The one exception to my preference for knobs is a logic analyzer. Keyboards and mice are better for those because there’s a lot of data entry. Make sure you get one that can handle I/O protocols. You’ve gotten recommendations for Saelig and Digilent. Both are good, entry-level, PC-based logic analyzers. It’s really going to depend on how many channels you think you need.”
That was my answer. In a bit, I’ll ask you to leave your comments and recommendations below. However, I thought I might elaborate on my answers here in EEJournal, where I have more room to opine.
Regarding my preference for knobs:
When you are positioning a waveform on a screen, setting trigger levels, or moving through timebase settings on a ‘scope, nothing beats knobs. Ditto for sweeping a frequency on a signal generator. I don’t really care if it’s a real rotary switch (increasingly rare), a rotary encoder (increasingly common), or a pot, if it turns with two fingers, it’s a knob. Fiddling with a mouse and clicking up/down arrows just does not provide the same sort of experience.
Also, knobs don’t lose their setting when you switch the ‘scope off. They’re still set the same way when you turn the ‘scope on. They have mechanical memory. Oops, that’s true of analog ‘scopes, but not newfangled digital ‘scopes with incremental rotary encoders. Sigh.
So what did I buy for my own lab? Five years ago, I bought a 2-channel Siglent Technologies SDS1202X-E 200 Mhz digital ‘scope from Amazon for $399. (They’re $20 cheaper right now.) The SDS1202X-E is truly a nice digital ‘scope. If you’d told me I could get that much ‘scope for $400 forty years ago, I’d have asked, “What’s a digital ‘scope?” We didn’t have them back then, not for any price. Back then, I wanted a Tektronix 465. That’s still a nice ‘scope, by the way.
The Siglent SDS1202X-E ‘scope lacks a built-in logic analyzer and that’s OK with me. I’m not a big proponent of cramming a lot of captured information on one screen, and the Siglent ‘scope has a relatively small screen anyway. Hey, it’s cheap, er… inexpensive. I much prefer a separate ‘scope and logic analyzer with good cross-triggering capabilities through external trigger ports. It’s a preference. Yours might differ.
I also prefer knobs on power supplies, but that’s only because I generally don’t have to worry about using a lab power supply to set 0.85-volt SoC core voltages. When you’re providing ±12 volts to an op amp, 12.05, 11.95, or even 12.1 volts is plenty good enough. However, there’s something to be said for programmable lab power supplies with digitally settable current limiting. I’ve wished for a current-limited lab supply more than once as I watch the magic smoke escape from my circuitry. I’m told by my friend Robert Bielby that the Siglent SPD3303X-E 3-channel DC power supply is a nice one and that it’s even good for audio work.
I’ve picked up several used GW Instek GPS-1850 and GPS-3030 single-output, linear power supplies from a local liquidator for $50 each. I prefer for these supplies to have analog meters because that kind of display helps me visualize what’s happening with the voltage setting and current output. But, admittedly, I am old school. Again, I haven’t needed the high resolution of a digital display here, but some home gamers might.
You’ve seen my stated preference for Fluke multimeters above. They’re built like tanks. I’ve had mine for nearly 40 years. It’s only a 3.5-digit Fluke 77, but it has served me well with very little care. It’s happy if I feed it a 9-volt battery every decade or so. That’s all the maintenance it gets.
Does that mean I’m completely faithful to Fluke when it comes to multimeters? Not at all. When Harbor Freight was giving away 3.5-digit Cen-Tech multimeters for free with a coupon, I collected these meters wholesale. I must have a dozen or so of these meters in a box somewhere. If you need to monitor a bunch of supply voltages in a circuit all at the same time, a box of free, reasonably accurate multimeters is a great way to do it.
I’ve checked their voltage accuracy against much more expensive meters, and the Cen-Tech meters were good enough for the work I do. A free meter is an expendable meter, just don’t use it in any high-voltage or high-current situations. Don’t bet your life or your safety on a cheap meter. And don’t ever pay actual money for one of these cheap Harbor Freight meters. (Actually, many, many vendors sell the same meter with different logos.) The current price for this meter at Harbor Freight is $6.99, but if you’re going to pay real money, buy a better meter.
I’ve also gone cheap when it comes to higher resolution multimeters. I spent less than $40 on a 4.5-digit Surpeer AV4 meter from Amazon five years ago. You can’t buy this meter any longer, but out of the box, its accuracy stacked up fine against an HP, er… Agilent, er… Keysight 34401 calibrated bench multimeter. I have no idea about the long-term accuracy of the Surpeer, and there’s no way to repair or calibrate it anyway, so when it dies, it dies. Meanwhile, it was a solid $40 investment. I like it and I use it when I want more resolution than I can get from my Fluke 77.
My last word on multimeters: I’d love a used HP 3478A in good working order. I just don’t need one. But if I needed a good multimeter, I’d buy a used HP 3478A.
Finally, there are logic analyzers. I’ve used logic analyzers since HP first came out with the incredibly primitive 1607A analyzer. That instrument didn’t even have a display. It drove both of an analog ‘scope’s inputs to create a vector XY display of ones and zeroes on the ‘scope screen. Virtually useless. However, a production prototype of the HP 1615A logic analyzer borrowed from HP’s Colorado Springs Division pulled my butt out of the fire in 1978 when troubleshooting a DMA glitch on the HP 9845A desktop computer. That glitch was the last bug to be solved before the machine could be released to production, and no one could find it. The HP 1615A logic analyzer’s newly invented glitch-capture feature caught the problem in less than 15 minutes, and the HP 9845A desktop computer shipped on time as a result.
So yes, I’m bragging that I’ve got as much experience (in terms of years) as anyone might have with logic analyzers, and I have my preferences. If you want an easy time finding hard-to-catch digital bugs, you’ll want to carefully label every signal you monitor. You don’t want to remember that A0 means the clock and A1 is data line zero. Also, if you’re hunting elusive bugs, you will likely need to set up some relatively complex triggers. These tasks are best done with a keyboard and mouse. If you need to monitor many signals, you need a high-resolution display.
For these reasons, I prefer a computer-driven logic analyzer. Early versions of PC-based logic analyzers weren’t very good, and there are still plenty of toy analyzers on the market that I would not buy. But the state of the art for PC-based logic analyzers has moved onward and upward. I think many of the new ones are pretty good, and they’re fabulous bargains for the money.
You can get 16-channel logic analyzers that are basically just FPGAs in a box for less than $200 on Amazon. Fast, highly parallel FPGAs were virtually made to become logic analyzers. Did I mention that my Senior Lab design project in college was a logic analyzer? That was way back in 1974. I wish I’d had an FPGA for that design, but they weren’t invented until 11 years later.
Finally, I’d be remiss if I didn’t talk about the Red Pitaya. This most unlikely instrument is also based on an FPGA, or more properly a Xilinx Zynq SoC, which melds Arm processors with FPGA fabric. Red Pitaya bills its eponymous device as the Swiss Army knife of instruments. It’s a programmable instrumentation platform with a couple of 125-Msamples/sec analog inputs and lots of digital I/O. Because it’s based on an FPGA, you literally program the Red Pitaya to be the instrument you need at the time. The Red Pitaya can be a ‘scope, a signal generator, a spectrum analyzer, a Bode analyzer, a logic analyzer, an LCR meter, or a vector network analyzer. Need a new instrument? You can design it and write a new configuration program. Just like a Swiss Army knife, the Red Pitaya isn’t the best at doing any of these tasks, but it can perform a lot of different test and measurement jobs, and it costs less than $300. It has no knobs or a display, or even an enclosure, however. It’s strictly a bare-bones, PC-based instrument.
Those are my recommendations for a home lab. Why not leave your recommendations in the comment section below?
Note: The workbench shown at the beginning of this article is the author’s HP workbench, circa 1978. Except for the soldering iron, the HP 180C “fat beam” ‘scope, and the 8-inch floppy disk drive, I’d still be happy to have most of that equipment. Note the absence of a logic analyzer. In those days, we had only one for a lab full of engineers.