Open Source LXI Tools Free Us From Vendor Bloat

February 18, 2022 by Dave Rowntree 8 Comments

LXI, or LAN eXtensions for Instrumentation is a modern control standard for connecting electronics instrumentation which supports ethernet. It replaces the older GPIB standard, giving much better performance and lower cost of implementation. This is a good thing. [Martin Lund] has created the open source lxi-tools project which enables us to detach ourselves from the often bloated vendor tools usually required for talking LXI to your bench equipment. This is a partial rewrite of an earlier version of the tool, and now sports some rather nice features such as mDNS for instrument discovery, support for screen grabbing, and a LUA-based scripting backend. (API Link)

SCPI or Standard Commands for Programmable Instruments is the text-based language spoken by many instruments, allowing control and querying of an instrument. Just to be clear, SCPI is not at all a new thing, and older instruments that have GPIB or RS232 connectors, still could talk SCPI. lxi-tools is not for those. Some instruments can also be very picky about the formatting of commands, especially if they’re buggy, so the ability to interactively debug commands is very desirable. It is quite possible to make poor use of SCPI commands in your test script and end up with tests that just take far longer to execute that they need to. lxi-tools has a benchmarking tool too, which helps you to dig in and find out where all the time is going and make suitable adjustments.

We’ve not seen much about LXI on Hackaday, but we did cover using PyVISA for dealing with SCPI-over-GPIB in python. If you have an older instrument with GPIB and you don’t want to sell a internal organ to pay for a USB adaptor, here’s one you can make yourself.

Fluke DMM Hack Adds One Digit To Model Number

February 7, 2022 by Chris Lott 28 Comments

Among his many interests, [Dave Jones] likes test and measurement equipment. He recently posted a few videos on his EEVblog exploring the reasons why Fluke voltmeters are so expensive. In the process, he stumbled upon an interesting hack for the Fluke 77.

The Fluke 77 was introduced in 1983, and is an average responding meter in the AC modes. This model has become a de-facto standard for use in maintenance depots and labs for equipment which has very long lifespans — think military and industrial gear, for example. Many test procedures and training materials have been designed around the use of the the Fluke 77. The cost to change them when a new and better meter comes along is usually so prohibitive they might as well be cast in stone — or at least hammered into 20 pound fanfold paper by a WordStar-driven daisy-wheel printer. But for those unburdened by such legacy requirements, Fluke has the 17x series of True RMS reading meters from since the beginning of this century. These meters bear a strong visual resemblance to their siblings in the 7x family and are substantially interchangeable but for their AC measurement methods. Continue reading “Fluke DMM Hack Adds One Digit To Model Number” →

Save Money And Have Fun Using IEEE-488

January 31, 2022 by Chris Lott 32 Comments

A few months ago, I was discussing the control of GPIB equipment with a colleague. Based on only on my gut feeling and the briefest of research, I told him that the pricey and proprietary GPIB controller solutions could easily be replaced by open-source tools and Linux. In the many weeks that followed, I almost abandoned my stance several times out of frustration. With some perseverance, breaking the problems into bite-sized chunks, and lots of online searching to learn from other people’s experiences, my plan eventually succeeded. I haven’t abandoned my original stance entirely, I’ve taken a few steps back and added some qualifiers.

What is GPIB?

Example of HP-IB block diagram from the 1970s, from hp9845.net

Back in the 1960s, if test equipment was interconnected at all, there weren’t any agreed-upon methods for doing so. By the late 60s, the situation was made somewhat better by card-cage controller systems. These held a number of interface cards, one per instrument, presenting a common interface on the backplane. Although this approach was workable, the HP engineers realized they could significantly improve the concept to include these “bridging circuit boards” within the instruments and replacing the card cage backplane with passive cables. Thus began the development of what became the Hewlett-Packard Interface Bus (HP-IB). The October 1972 issue of the HP Journal introduced HP-IB with two main articles: A Practical Interface System for Electronic Instruments and A Common Digital Interface for Programmable Instruments: The Evolution of a System. Continue reading “Save Money And Have Fun Using IEEE-488” →

Multimeters Go Big Screen

December 7, 2021 by Al Williams 54 Comments

We’ve noticed lately that some cheap meters have gone to having big colorful screens. The screens aren’t dot matrix, but still have lots of graphics that could be useful or could be distracting eye candy, depending. The really cheap ones seem more like a gimmick, but [OM0ET] took a look at one that looked like a fair midrange instrument with some useful display features, the GVDA GD128.

A lot of the display shows the current function of the meter. No need for an expensive multiposition switch or rows of interlocking pushbuttons. Many of these new meters also have non-contact voltage sensors, which is handy. Otherwise, it looks like a pretty conventional cheap meter. Continue reading “Multimeters Go Big Screen” →

Chip Tester Knows If Your Old Chips Are Working

October 23, 2021 by Al Williams 6 Comments

[Noel’s Retro Lab] has looked at retro chip testers before, but in a recent video you can see below he’s looking at the Chip Tester Pro, a preassembled chip tester for vintage chips, especially those used in Commodore computers. The device looks good on the surface with a form factor like a calculator or cell phone, an LCD display, and a 48 pin ZIF socket.

The user interface is pretty simple. A rotary encoder and a big red button are about it. However, there are also some headers where you have to use jumpers to wire signals to the chip. The firmware gives you specific directions, but it is reminiscent of programming old punchcard machines with jumper wires. Luckily, it looks like you only route the power to the device so you don’t have many wires to connect (usually two or three).

Continue reading “Chip Tester Knows If Your Old Chips Are Working” →

Mystery HP Gear Teardown

October 22, 2021 by Al Williams 6 Comments

What’s round, has what looks like a vacuum tube in the center, and was made in the 1950s by HP? We don’t know either, but [The Signal Path] restored one and shows us this mystery instrument in a recent video that you can see below. We aren’t going to spoil the surprise over what the device is, but we will share that he does reveal what it is very early in the video, so there’s not much of a tease.

We will, however, give you a few hints. Looking at it, you can guess that it is meant for high voltage use and, in fact, it is rated for up to 25 kV. We’ll also drop the hint that it is made for use with AC, not DC. The shape of the plug at the end of the wire is also a clue, we think.

There isn’t much inside the unusual round case (another clue, by the way), but there are some vintage parts we haven’t seen in quite awhile. One last clue: Why is there a metal rod and ball sticking out of one side of the device?

Honestly, the insides are a bit underwhelming so unlike some teardown videos we’ve seen, the real star of this video is the unusual device more so than its inner workings. If you have a hankering for a more sophisticated HP exploration, check out the HP3458A repair we covered earlier. Or go old school and peek inside an HP 150A.

Continue reading “Mystery HP Gear Teardown” →

Custom Isolated Variac Is Truly One Of A Kind

August 17, 2021 by Tom Nardi 32 Comments

It’s no surprise that many hardware hackers avoid working with AC, and frankly, we can’t blame them. The potential consequences of making a mistake when working with mains voltages are far greater than anything that can happen when you’re fiddling with a 3.3 V circuit. But if you do ever find yourself leaning towards the sparky side, you’d be wise to outfit your bench with the appropriate equipment.

Take for example this absolutely gorgeous variable isolation transformer built by [Lajt]. It might look like a high-end piece of professional test equipment, but as the extensive write-up and build photographs can attest, this is a completely custom job. The downside is that this particular machine will probably never be duplicated, especially given the fact its isolation transformer was built on commission by a local company, but at least we can look at it and dream.

This device combines two functions which are particularly useful when repairing or testing AC hardware. As a variable transformer, often referred to as a variac, it lets [Lajt] select how much voltage is passed through to the output side. There’s a school of thought that says slowly ramping up the voltage when testing an older or potentially damaged device is better than simply plugging it into the wall and hoping for the best. Or if you’re like Eddie Van Halen, you can use it to control the volume of your over-sized Marshall amplifiers when playing in bars.

Secondly, the unit isolates the output side. That way if you manage to cross the wrong wire, you’re not going to pop a breaker and plunge your workshop into darkness. It also prevents you from accidentally blowing up any AC powered test equipment you might employ while poking around, such as that expensive oscilloscope, since the devices won’t share a common ground.

Additional safety features have been implemented using an Arduino Uno R3 clone, a current sensor, and several relays. The system will automatically cut off power to the device under test should the current hit a predetermined threshold, and will refuse to re-enable the main relay until the issue has been resolved. The code has been written in such a way that whenever the user makes a configuration change, power will be cut and must be reestablished manually; giving the user ample time to decide if its really what they want to do.

[Lajt] makes it clear that the write-up isn’t meant as a tutorial for building your own, but that shouldn’t stop you from reading through it and getting some ideas. Whether you’re in the market for custom variac tips or just want to get inspired by an impeccably well engineered piece of equipment, this project is a high-water mark for sure.