Vintage Multimeter Gets An LCD Transplant

March 8, 2022 by 10 Comments

Hackers are often of the sentimental type, falling in love with the look and feel of quality old hardware. Of course, sometimes that older hardware needs a little TLC to keep it running in the modern world. [Lex] had a beautiful vintage multimeter that sadly had a broken screen, and set about a nifty repair to restore it to working condition. 

It’s a handsome thing.

The HSN Avometer DA116 is a handsome thing, controlled with two dials and featuring a clean two-tone aesthetic. Even the font on the PCB’s silkscreen is gloriously pretty (can anyone ID that?). However, the original LCD was non-functional. A direct replacement part was sadly unavailable. Instead, to rectify this, [Lex] first hunted down another segmented LCD screen that had the same segment layout.

However, the new screen had a completely different pinout to the original part. Thus, after taking some notes and figuring out what all the pins did, [Lex] whipped up an adapter board to carry the new screen. With some protoboard, some pin headers, and a bunch of point-to-point wiring, the new screen worked just fine, and [Lex] had a functioning vintage meter once again!

The story actually came to us on Twitter, where we invited discussion about the best bodge wiring jobs out there. Feel free to contribute your own stories to the conversation! If you’re in the market for more LCD hacking, be sure to check out the excellent talk [Joey Castillo] gave at the 2021 Remoticon.

Receiver board of the Ethernet tester, with only probing pins, and no resistors populated

Ethernet Tester Needs No LEDs, Only Your Multimeter

February 28, 2022 by 27 Comments

Ethernet cable testers are dime a dozen, but none of them are as elegant and multimeter-friendly as this tester from our Hackaday.io regular, [Bharbour]. An Ethernet cable has 8 wires, and the 9 volts of easily available batteries come awfully close to that – which is why the board has a voltage divider! On the ‘sender’ end, you just plug this board onto the connector, powered by a 9 volt battery. On the “receiver” end, you take your multimeter out and measure the testpoints – TP7 should be at seven volts, TP3 at three volts, and so on.

As a result, you can easily check any of the individual wires, as opposed to many testers which only test pair-by-pair. This also helps you detect crossover and miswired cables – while firmly keeping you in the realm of real-life pin numbers! This tester is well thought-out when it comes to being easily reproducible – the PCB files are available in the “Files” section, and since the “receiver” and “sender” PCBs are identical, you only need to do a single “three PCBs” order from OSHPark in order to build your own!

Bharbour has a rich library of projects, and we encourage you to check them out! If you ever want to get yourself up to speed on Ethernet basics, we’ve talked about its entire history – and we’ve even explained PoE! After some intensive learning time, perhaps you can try your hand at crimping the shortest Ethernet cable ever.

An analog multimeter being used as a ping display

Classic Multimeter Tells You If Your WiFi’s Working

February 22, 2022 by 14 Comments

Debugging network issues isn’t easy; many a sysadmin has spent hours trying to figure out which of the many links between client and server is misbehaving. Having a few clear pointers helps: if you can show that the  internet connection is up, that already narrows down the problem to either the server or, most likely, the client computer.

After hearing “is the internet up” one too many times, [whiskeytangohotel] decided to make a clearly visible indicator to show the status of the local uplink. He used his father’s old Simpson 260 VOM as a display, with its large analog indicator pointing at a steady value if the internet’s up, and wagging back and forth if there’s an outage. The exact value indicated is determined by the average ping time for a couple of different servers, so that you can also tell if the connection is slower than normal.

The ping times are measured by an ESP8266 connected to WiFi, which checks a predefined list of web servers and calculates the average ping time every fifteen seconds. An analog value in the 2.5 V range is then generated and measured by the meter. The smooth motion of an old analog meter stands in nice contrast to the modern-day problem of unstable WiFi.

While analog multimeters definitely have their uses, we’re the first to admit that our classic meters don’t see as much action as they could. Repurposing them as [whiskeytangohotel] did is a neat way of keeping those heirlooms around for the next generation. Of course, if you don’t have an analog multimeter, you could also use an analog clock for your ping meter. Continue reading “Classic Multimeter Tells You If Your WiFi’s Working” →

Multimeters Go Big Screen

December 7, 2021 by 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” →

The HP3458A: King Of Multimeters For Three Decades

October 18, 2021 by 16 Comments

[Marco] looks at a lot of meters. However, he considers the HP3458A the best even though they were introduced more than 30 years earlier in 1989. Someone donated one to [Marco] but it presented some error messages on startup and exhibited erratic behavior, so he had some repairs to do.

The error codes hinted there were issues with the multislope analog to digital converter and that’s what sets the meter apart, according to [Marco]. The meter has 8.5 digits, so a normal conversion stage won’t cut it.

Continue reading “The HP3458A: King Of Multimeters For Three Decades” →

Hackaday Podcast 127: Whippletree Clamps, Sniffing Your Stomach Radio, Multimeter Hum Fix, And C64 Demo; No C64

July 16, 2021 by No comments

Hackaday editors Mike Szczys and Elliot Williams help you get caught up on a week of wonder hacks. We don’t remember seeing a floppy drive headline the demoscene, but sure enough, there’s a C64 demo that performs after the computer is disconnected. What causes bench tools to have unreliable measurements? Sometimes a poor crystal choice lets AC ruin the party. We dive into the ongoing saga of the Audacity open source project’s change of ownership, and talk about generator exciter circuits — specifically their role in starting grid-scale generators from shutdown.

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Direct download (60 MB or so.)

Places to follow Hackaday podcasts:

Continue reading “Hackaday Podcast 127: Whippletree Clamps, Sniffing Your Stomach Radio, Multimeter Hum Fix, And C64 Demo; No C64” →

Fixing Noisy Measurements On An Owon XDM2041 Bench Multimeter

July 14, 2021 by 21 Comments

After purchasing an Owon XDM2041 bench multimeter for an automated test setup, [Petteri Aimonen] was disappointed to find that at especially the higher mega Ohm ranges, the measured values were jumping around a lot and generally very inaccurate. Since this is an approximately $170 bench multimeter and Owon support wasn’t cooperating, [Petteri] set out to fix the issue, starting with a solid teardown.

As noted by [Petteri], there’s not a whole lot inside one of these multimeters. The main board with the guts of the whole system contains a GigaDevices GD32F103CBT6 MCU coupled with the star of the show: the HYCON Technology Corporation’s HY3131 multimeter chip. After a peek at the HY3131 datasheet, the culprit was quite apparent: while sampling the presence of mains voltage noise is usually suppressed through the selection of an appropriate crystal.

Unfortunately, instead of the recommended 4.9152 MHz crystal per the reference schematic for the HY3131, Owon’s engineers had apparently opted for a 4 MHz crystal instead, and so it’s essentially aliasing the line noise.

[Petteri] figured that the resulting sampling timing might work well enough with 60 Hz line frequency, but clearly with 50 Hz there was a lot of noise sneaking into the measurements. After swapping the crystal with a 3.072 MHz one, there was a marked improvement, as the plot shows.