When a fine piece of lab instrumentation crosses your bench, you’ve got to do your best to put it to work. But even in the highest quality devices no component lasts forever, especially vacuum tubes. For some vintage instruments with vacuum fluorescent displays, that means putting up with less-than-perfect digits in order to get that sweet, sweet precision. Or not – you can always reverse engineer the thing and add a spanking new OLED display.
The Hewlett-Packard 34401A digital multimeter that fell into [qu1ck]’s lap was a beauty, but it had clearly seen better days. The display was full of spuriously illuminated dots and segments, making it hard to use the 6.5 digit DMM. After a futile bit of probing to see if a relatively easy driver fix would help, and with a replacement display being made of solid unobtanium, [qu1ck] settled in for the long process of reverse engineering the front panel protocol. As luck would have it, H-P used the SPI protocol to talk to the display, and it wasn’t long before [qu1ck] had a decent prototype working. The final version is much more polished, with a display sized to fit inside the original space occupied by the VFD. The original digits and annunciator icons are recreated, and he added a USB port and the bargraph display show in the clip below.
We think it looks fabulous, and both the firmware and hardware are on Github if you’d like to rescue a similar meter. You may want to check our guide to buying old test gear first, though, to get the most bang for your buck.
Continue reading “Faded Beauty DMM Gets An OLED Makeover”
Have you ever been so frustrated with a digital display that you wanted to rip the whole thing out and create a better one? That is exactly what [xi] did. Replacing their constantly used HP 3457A multimeter’s LCD display with a brighter LED one was a necessary project — and a stress reducing one at that.
While this digital multimeter is well-known for its reliability, its standard display is rather lacking. In fact, there are several mods already out there that simply add a backlight. However, as [xi] notes, LCD screens always have a certain angle where they still don’t quite show properly. So this hack reverses the LCD’s protocol and details the process of creating new LED display.
The issue of dim displays that comes with traditional digital multimeters is not a new one. One solution to this that we have seen before is a hack where someone decided to add a backlight onto their cheap multimeter. [Ken Kaarvik] got around the dimness altogether by giving his multimeter a wireless remote display of his choosing. It is interesting to see the different solutions that are made to the same nuisance. The first item on the agenda of [xi]’s hack was to successfully analyze the HP LCD protocol. With the aid of an ATmega32, the digits were decoded throughout the transmission frames.
Continue reading “LEDs Give HP 3457A DDM’s LCD Display the Boot”
[Dannyelectronics] sometimes needs to measure tiny currents. Really tiny, like leakage currents through a capacitor. He’s built a few setups to make the measurements, but he also knew he’d sometimes want to take readings when he didn’t have his custom gear available. So he decided to see what he could do with an ordinary digital meter.
As you might expect, a common digital meter’s current scales aren’t usually up to measuring nano- or pico-amps. [Danny’s] approach was not to use the ammeter scale. Instead, he measures the voltage developed across the input impedance of the meter (which is usually very high, like one megaohm). If you know the input characteristics of the meter (or can calibrate against a known source), you can convert the voltage to a current.
For example, on a Fluke 115 meter, [Danny] found that he could read up to 60nA with a resolution of 0.01nA. A Viktor 81D could resolve down to 2.5pA–a minuscule current indeed.
We’ve looked at the difficulties involved in reading small currents before. If tiny currents aren’t your thing, maybe you’d like to try charging an iPhone with 3 KA, instead.
After a request from one of his friends, [Mastro Gippo] managed to put together a talking multimeter to be used by blind persons working in electronics. He wanted a feature-rich meter that had serial output, and recalling this Hackaday article from a few years back led him to find a DT-4000ZC on eBay, which has serial output on a 3.5mm jack. (Though, he actually recommends this knockoff version which comes with excellent documentation).
It turns out there aren’t many talking meter options available other than this expensive one and a couple of discontinued alternatives. [Mastro Gippo] needed to start from scratch with the voice synthesizer, which proved to be as easy as recording a bunch of numbers and packing them onto an SD card to be read by an Arduino running the SimpleSDAudio library.
He found a small, battery-powered external speaker used for rocking out with music on cell phones and hooked it up to the build, stuffing all the electronics into an aluminum case. Stick around after the jump for a quick video of the finished product!
Continue reading “Say Watt? A Talking Multimeter?”
Fluke just issued a response to the impounding of multimeters headed for market in the United States. Yesterday SparkFun posted their story about US Customs officials seizing a shipment of 2000 multimeters because of trademark issues. The gist of the response is that this situation sucks and they want to do what they can to lessen the pain for those involved. Fluke is providing SparkFun with a shipment of genuine Fluke DMMs which they can sell to recoup their losses, or to donate. Of course SparkFun is planning to donate the meters to the maker community.
Anyone with a clue will have already noticed the problem with this solution. The impounded shipment of 2k meters will still be destroyed… eh. The waste is visceral. But good for Fluke for trying to do something positive.
Before we sign off let’s touch on the trademark issue for just a moment. We can’t really blame Fluke too much for this. The legal crux of the matter is you either defend your trademark in every case, or you don’t defend it at all. In this case it was the border agents defending the filing, but for ease of understanding we’ll not go into that. On the other hand, speaking in general business terms, the way things are set up it is advantageous to acquire a trademark specification that is as broad as possible because it helps to discourage competitors from coming to market. So trademark is good when it keep hucksters from trying to rip off consumers. But it is bad if applied too broadly as a way of defending a company’s market share.
Where does Fluke come down in all of this? Who knows. There is literally no right answer and that’s why the discussion around yesterday’s post was full of emphatic arguments. A Fluke meter is a cream-of-the-crop device and they have the right (and obligation) to ensure that reputation is not sullied. SparkFun serves a market that probably can’t afford a Fluke at this time but may some day in the future. And this is the reason we can feel okay about this outcome.
Check out this SparkFun Digital Multimeter. Does it make your blood boil to see them ripping off Fluke by using the color yellow? From SparkFun’s side of the story that’s exactly what’s happened here. They have a shipment of 2000 of these things stuck in customs. The trademark being infringed upon can be found in their article. Fluke owns the trademark on multimeters with a dark face and yellow border. Great. This seems like a wonderful idea, right up there with Apple owning tablets that are shaped like a piece of paper.
Okay, so if you’re not crying big fat tears for Fluke being taken advantage of in this way let’s talk about more immediate issues than fixing trademark, patent, copyright, and all of the other screw-the-little-guy type of laws (not that SparkFun is necessarily the little guy but you know what we mean). The DMMs sitting in a warehouse are costing SparkFun $150 per day. We believe they have no option of choosing a warehouse with a lower cost as we must be talking a pallet or two, right? The only two options they do have are shipping them back to China where they were manufactured, or having them destroyed. The former will cost more in re-import tariffs than the cost of the product, and the latter comes with a $150/hour disposal fee and no metric on which to judge how long it would actually take. We hate seeing this kind of waste, but sure enough 2000 DMMs are headed for the shredder in a couple of days.
We know you already have your flaming sword in hand, but simmer down for just a second. Fluke makes great products, ask anyone. And companies the world over defend their trademarks. Hopefully there will soon be a positive response from Fluke on this one. If you would like to politely encourage them to do the right thing we found Fluke’s Facebook page URL in the SparkFun comments thread. Both are worth browsing.
[Thanks Chris via Reddit]
We would like to share a bit of good news; Collin’s Lab is back on the airwaves of the Internet. If you didn’t know, [Collin Cunningham] previously created excellent short videos, sometimes entertainingly tongue-in-cheek, for Make Magazines on the subjects of electronic components and fundamental electronics. In 2012 he was hired at Adafruit as a Creative Engineer to help with software development and video production.
Going forward Collin’s Lab videos will be a regular feature on Adafruit’s Blog and their YouTube channel. We’re sure there is going to be tons of entertaining learning from Collin with his unique video production skills and presentation delivery.
This first release of Collin’s Lab on Adafruit is a primer review covering fundamental multimeter functionality and measurements. Not much here for the medium to advanced electronics hacker but for the beginner this is an excellent and quick way to learn the basics on using your multimeter.
If you want to checkout Collin’s older video productions you can find them on his Narbotic Instruments site under – “Make Presents” and “Collin’s Lab” or watch them all with this convenient playlist. Just after the break you can also watch his latest edition of Collin’s Lab.
Continue reading “Collin’s Lab is Coming Back”