oscilloscope

277 Articles

Dead Simple Time-Domain Reflectometry With Just A Battery And An Oscilloscope

December 14, 2020 by 30 Comments

“Time-domain reflectometry” sure sounds like something that needs racks of expensive equipment to accomplish. In reality, TDR is just measuring the time between injecting a pulse into a cable and receiving its echo, either from the other end of the cable or from some fault or defect along the way. It’s a useful technique, and as [Allen Wolke (W2AEW)] shows us, it can be accomplished with little more than a battery, a resistor, and an oscilloscope. And a little math, of course.

There are, of course, dedicated time-domain reflectometers, but all of them are really just elaborations of the basic principles [W2AEW] demonstrates with his simple setup. The oscilloscope is set up with a tee connector on one channel; one side of the tee is connected to the cable under test, while the shield conductor of the other side is connected to the negative terminal of a 9V battery. A resistor connected to the center conductor is used to complete the circuit, which sends a brief pulse down the test cable. The scope is set up to capture the outgoing pulse as well as the return pulse, allowing the time between the two to be measured. Some simple math gives the length of the cable, the distance to a fault, or with a little rearrangement, the velocity factor of the cable.

The video below shows the simple method at work on coax and Cat 5e Ethernet cable. It even worked on a roll of zip cable, which was a little surprising. If this technique is too simple, you can always elaborate a bit and roll your own TDR tester. Googly eyes optional, of course, but recommended.

Continue reading “Dead Simple Time-Domain Reflectometry With Just A Battery And An Oscilloscope” →

Cardboard Models Trace Design Process Of Vintage Tektronix Miniscopes

October 22, 2020 by 11 Comments

There aren’t many brands that inspire the kind of passion and fervency among its customers as Tektronix does. The venerable Oregon-based manufacturer of top-end test equipment has produced more collectible gear over the last 75 years than just about anyone else.

Over that time they have had plenty of innovations, and in the 1970s they started looking into miniaturizing their flagship oscilloscopes. The vintageTEK museum, run by current and former employees, has a review of the design process of the 200 series of portable oscilloscopes that’s really interesting. At a time when scopes were portable in the way a packed suitcase is portable, making a useful instrument in a pocketable form factor was quite a challenge — even for big pockets.

The article goes into great detail on the back-and-forth between the industrial designers, with their endless stream of models, and the engineers who would actually have to stuff a working scope into whatever case they came up with. The models from the museum’s collection are wonderful bits of history and show where the industrial designers really pushed for some innovative designs.

Some of the models are clearly derived from the design of the big bench scopes, but some have innovative flip-down covers and other interesting elements that never made it to production. Most of the models are cardboard, but some were made of aluminum in the machine shop and sport the familiar “Tek blue” livery. But the pièce de résistance of the collection is a working engineering model of what would become the 200-series of miniscopes, a handmade prototype with a tiny round CRT and crudely labeled controls.

The vintageTEK museum sounds like another bucket-list stop for computer and technology history buffs. Tek has been doing things their own way for a long time, and stopping by the museum is sure to be a treat.

Thanks to [Tanner Bass] for the tip.

Upgrading A Classic Function Generator

October 20, 2020 by 8 Comments

If you need an oscilloscope, function generator, or other piece of kit for your electronics workbench, there are plenty of modern options. Dropping $4,000 for a modern oscilloscope is nice if you have the money, but if you’d rather put it to better use there are great options that don’t cost a fortune. There are some addons that can turn a smartphone into an oscilloscope but one of the best values out there are older pieces of equipment from the 80s that still work great. You can even upgrade them with some more modern features too, like [NFM] did with this vintage function generator.

This function generator is an HP3325A and it is several decades old, so some work was needed just to restore it to original working condition. The cooling fan and capacitors all needed to be replaced, as well as a few other odds and ends. From there [NFM] set about adding one of the two optional upgrades available for this device, the high voltage output. This allows the function generator to output 40 volts peak-to-peak at 40 milliamps. While he did have an original version from HP, he actually had a self-made design produced that matches the function of the original.

Even if you don’t have this specific function generator, this guide goes into great details about the functioning of older equipment like this. Most of the parts are replaceable and upgrades aren’t completely out of the question like some modern equipment, and with the right care and maintenance these pieces of equipment could last for decades longer.

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Toy O-Scope Is Dope

September 12, 2020 by 12 Comments

Not many of our childhood doll and action figure’s accessories revolved around lab equipment except maybe an Erlenmeyer flask if they were a “scientist.” No, they tended to be toasters, vehicles, and guns. When we were young, our heroes made food, drove sexy automobiles, and fought bad guys. Now that we’re older, some of our heroes wield soldering irons, keyboards, and oscilloscopes. [Adrian Herbez] made a scale model oscilloscope that outshines the beakers and test tube racks of yesteryear. Video also shown below. Continue reading “Toy O-Scope Is Dope” →

Antique Oscilloscope Gets New Home And Purpose

September 1, 2020 by 11 Comments

As the pace of technology charges blindly forward, a lot of older tools or products get left in the dust, forgotten to most but those left with them. This doesn’t mean they’re useless, though. In fact, old technology that continues to survive in the present tends to be more robust and sturdy than most modern, cheap replacements. While this might be survivorship bias, this is certainly true in particular of oscilloscopes. Rugged CRTs in large metal housings with discrete through-hole components in simple layouts made them reliable, but they’re heavy, bulky, and lack features of modern instruments. With some modifications, though, you can give them a new home and keep their vintage aesthetic.

[BuildComics] had just such an oscilloscope on hand and set out to make it into something useful but aesthetically pleasing as well. With a small circuit board, formerly available as a kit from Sparkfun/Dutchtronix but now only available if you can build them yourself, the cathode ray tube can be modified to output not waveforms but rather a working clock face. The donor oscilloscope was a Heathkit IO-102 which was fine for its time but is now lacking, so the CRT was removed from its housing and placed in a custom-built enclosure with a 40s radio style that suits its new purpose well.

Seeing old hardware that is past its prime being put to work in a new way is great, both from a technical standpoint and also because that’s usable hardware that’s being kept out of the landfill. Oscilloscopes are popular for projects like these too since they are relatively easy to understand and modify. Besides being used as clocks, we’ve also seen them modified to play video games such as Pac-Man.

Inside A $30,000 8 GHz Scope

July 29, 2020 by 20 Comments

One of the best things about the Internet — especially the video part — is that you can get exposed to lots of things you might otherwise not be able to see. Take oscilloscopes, for example. If you were lucky, you might have one or two really nice instruments at work and you certainly weren’t going to be allowed to tear them open if they were working well. [The Signal Path], as a case in point, tears down a $30,000 MSO6 8 GHz oscilloscope.

Actually, the base price is not quite $30,000 but by the time you outfit one, you’ll probably break the $30K barrier. Compared to the scopes we usually get to use, these are very different. Sure, the screens are larger and denser, but looking at the circuit boards they look more like some sort of high-end computer than an oscilloscope. Of course, in a way, that’s exactly what it is.

Continue reading “Inside A $30,000 8 GHz Scope” →

Upgrading The RAM In A 25 Year Old Oscilloscope

July 19, 2020 by 25 Comments

From reading his extensive write-ups on the subject, there’s one thing we know for sure: [Tom Verbeure] loves his Tektronix TDS 420A oscilloscope. While it might be older than some of the people reading this, it’s still an impressive piece of hardware with more than enough bells and whistles to keep the average hacker occupied. Especially if you’re willing to perform some hardware modifications.

Note the battery to retain calibration data.

[Tom] already knew how to tickle the scope into unlocking software features, a process not unlike what we’ve seen done on more modern scopes. But there’s only so far you can get by toggling software flags.

Some of the more advanced features that are turned off in the firmware actually need additional hardware to function. Simply bumping the sample points to 120,000 in software wasn’t enough, the scope actually needs the memory to hold them in.

Now logically, if there’s a software option to increase the number of samples, there must be a hardware upgrade that goes along with it. Sure enough, [Tom] found there were 6 open spots next to the scope’s existing M5M51008 static RAM ICs.

As luck would have it the chips are still available, albeit from a different manufacturer and a bit faster than the original parts. Digikey wouldn’t sell fewer than 100 of them, but UTSource was happy to sell him 10. In this case, the parts were cheaper than the shipping cost. Installation was about as straightforward as it gets, though [Tom] does note that he had to keep the board powered up during the operation or else the scope would have lost its calibration data.

Squeezing more features out of modern scopes like the Rigol DS2072A just takes a USB cable and some software. Sometimes it’s only a matter of tapping in a code. But we certainly appreciate [Tom] putting in a little extra effort to get the most out of this classic piece of hardware.