test equipment

98 Articles

Capturing Screenshots Using A Fake Printer

June 17, 2025 by 16 Comments

If you have very old pieces of analogue test equipment with CRTs on your bench, the chances are they will all have surprisingly similar surrounds to their screens. Back when they were made it was common to record oscilloscope screens with a Polaroid camera, that would have a front fitting for just this purpose.

More recent instruments are computerized so taking a screen shot should be easier, but that’s still not easy if the machine can’t save to a handy disk. Along comes [Tom] with a solution, to hook up a fake printer, and grab the screen from a print.

Old instruments come with a variety of ports, serial, IEE-488, or parallel, but they should usually have the ability to print a screen. Then capturing that is a case of capturing an interpreting the print data, be it ESC/P, PCL5, Postscript, or whatever. The linked page takes us through a variety of techniques, and should be of help to anyone who’s picked up a bargain in the flea market.

This isn’t the only time we’ve touched on the subject of bringing older computerized equipment into the present, we’ve also shown you a disk drive emulator.

Thanks [JohnU] for the tip.

PoE-powered GPIB Adapter With Ethernet And USB-C Support

May 10, 2025 by 9 Comments

In the world of (expensive) lab test equipment the GPIB (general purpose interface bus) connection is hard to avoid if you want any kind of automation, but nobody likes wrangling with the bulky cables and compatibility issues when they can just use Ethernet instead. Here [Chris]’s Ethernet-GPIB adapter provides an easy solution, with both Power over Ethernet (PoE) and USB-C power options. Although commercial adapters already exist, these are rather pricey at ~$500.

Features of this adapter include a BOM total of <$50, with power provided either via PoE (802.3af) or USB-C (5V-only). The MCU is an ATmega4809 with the Ethernet side using a Wiznet W5500 SPI Ethernet controller. There is also a serial interface (provided by a CH340X USB-UART adapter), with the firmware based on the AR488 project.

The adapter supports both the VXI-11.2 and Prologix protocols, though not at the same time (due to ROM size limitations). All design documents are available via the GitHub repository, with the author also selling assembled adapters and providing support primarily via the EEVBlog forums.

Homemade VNA Delivers High-Frequency Performance On A Budget

April 16, 2025 by 7 Comments

With vector network analyzers, the commercial offerings seem to come in two flavors: relatively inexpensive but limited capabilities, and full-featured but scary expensive. There doesn’t seem to be much middle ground, especially if you want something that performs well in the microwave bands.

Unless, of course, you build your own vector network analyzer (VNA). That’s what [Henrik Forsten] did, and we’ve got to say we’re even more impressed by the results than we were with his earlier effort. That version was not without its problems, and fixing them was very much on the list of goals for this build. Keeping the build affordable was also key, which resulted in some design compromises while still meeting [Henrik]’s measurement requirements.

The Bill of Materials includes dual-channel broadband RF mixer chips, high-speed 12-bit ADCs, and a fast FPGA to handle the torrent of data and run the digital signal processing functions. The custom six-layer PCB is on the large side and includes large cutouts for the directional couplers, which use short lengths of stripped coaxial cable lined with ferrite rings. To properly isolate signals between stages, [Henrik] sandwiched the PCB between a two-piece aluminum enclosure. Wisely, he printed a prototype enclosure and lined it with aluminum foil to test for fit and function before committing to milling the final version. He did note some leakage around the SMA connectors, but a few RF gaskets made from scraps of foil and solder braid did the trick.

This is a pretty slick build, especially considering he managed to keep the price tag at a very reasonable $300. It’s more expensive than the popular NanoVNA or its clones, but it seems like quite a bargain considering its capabilities.

Protocol Analyzer Remembered

March 30, 2025 by 22 Comments

Anyone will tell you that as hard as it is to create a working system, the real trick is making two systems talk to each other, especially if you created only one or none of them. That’s why tools that let you listen in on two systems talking are especially valuable.

If you were a well-funded lab back in the RS232 days, you might have an HP4957A protocol analyzer. The good news is that if you still use RS232, these kinds of things are now cheap on the surplus market. [IMSAI Guy] got one of these decidedly cool devices and shows it to us in the video below.

The look of these was pretty neat for their time—a folded-up instrument with a cute keyboard and a CRT-100. You can load different interpreters from ROM to RAM, such as the VT-100, which is essentially an application for the device. Of course, now you could rig one of these up in a few minutes with a PC or even a Pi Pico. But it wouldn’t have the same charm, we are sure you would agree.

You can find a lot of old RS232 gear around, from breakout boxes to advanced sniffers like this one. Too bad we couldn’t afford them when we really needed them.

This could be handy if you have a lot of ports. Either real or virtual. Or, do it yourself.

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Inside A “Budget” Current Probe

March 16, 2025 by 10 Comments

Current measurements are not as handy as voltage measurements. You typically need to either measure the voltage across something and do some math or break the circuit so a known resistor in your instrument develops a voltage your meter measures and converts for you. However, it is possible to get non-contact current probes. They are generally pricey, but [Kerry Wong] shows us one under $200 and, thus, budget compared to similar probes. Check out the review in the video below.

The OWON unit has three ranges: 4 A, 40 A, and 400 A. It claims a resolution of 10 mA and a bandwidth of 200 kHz. It requires a 9 V battery, which [Kerry] suspects won’t last very long given the rated power consumption number, although the measured draw was not as high as claimed. The specs aren’t great — this seems to be little more than a current probe meter with a connector for an oscilloscope, but if it meets your needs, that could be acceptable.

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A Look Inside A Modern Mixed Signal Oscilloscope

January 18, 2025 by 5 Comments

High-speed bench equipment has become so much more affordable in the last decade that naturally one wonders what has made that possible. A great source of answers is a teardown by users like [kerry wong] who are kind enough to take apart their MSO2304X 300MHz osilloscope for our viewing pleasure.

The posted teardown video shows the guts of the scope without enclosure, heatsinks and shields that reveal a handful of boards that execute the functions nicely. The motherboard uses the Xilinx KINTEX-7 FPGA that is expected to run core processes such as signal processing as well as managing the sample storage on the paired DDR3 memory.

The analog front-end here is a bit of a surprise as it sports TI’s ADC08D1000 ADCs that are capable of 1.3 GSPS but the scope is advertised to be capable of more. The inferred design is that all four ADCs are being operated in an interleaved symphony to achieve 5 GSPS. Testing confirms that each input uses two ADCs at a time and when two or more channels are employed, the reconstruction quality drops.

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Open Source Multimeter Raises The Bar For DIY Tools

December 25, 2024 by 39 Comments

Whether you only dabble in electronics as a hobby or it’s your full-time job, there are few tools as indispensable as the multimeter. In fact, we’d be willing to bet nearly everyone reading this site owns at least one of them. But as common and mindbogglingly useful as they may be, they aren’t perfect. Even the high-end models will invariably have some annoyance that only reveals itself once you become intimately acquainted with it.

Most people would just live with those quirks, especially when dealing with a cheaper model. But not [John Duffy]. Deciding nothing but perfection would do, he took every favorite feature he’d ever run into while using other multimeters and combined them into his scratch-built HydraMeter. In the process, he managed to come up with a few new ideas that push this device into a league of its own.

Some of the features of the HydraMeter will look familiar. You might even have them on your own personal meter, such as the wireless removable display module. Other features you’ll wish your meter had, such as the removable cartridge on the front of the device that lets you rapidly swap out a burned fuse. On the other side of the spectrum, there are some esoteric features that might leave you scratching your head. The ability to tell exactly how the meter is configured at a glance thanks to its exclusive use of toggle switches has a certain hacker appeal, but it’s a tricky user interface for most folks.

While the overall design of the HydraMeter may be divisive, one thing we can all agree on is that getting the project to this state took incredible determination. Over the years we’ve only seen a handful of individuals attempt to develop their own multimeters, and even then, none of them approached this level of fit and finish. The fact that [John] has turned all that effort over to the community by releasing his design under the CERN license is truly admirable.

[John] brought the HydraMeter out to Pasadena back in November for Supercon, and it got quite a reaction. And if you don’t like the user interface, it’s not hard to imagine how you could change it. This project has unquestionably pushed the state of the art for open source multimeters forward, and we’re eager to see where it goes from here.

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