[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.
We remember when buying even a modest digital multimeter was a big investment. These days, you can find tool stores giving away cheap meters and if you are willing to spend even a little money, you can buy a meter with tons of features like capacitance, temperature, and other measurements.
Like most things, though, you can pay a little money for a bargain, or you can overpay for a dud. To help you pick, [TechnologyCatalyst] decided to do an extensive video review of 15 different meters in the under $50 price category.
If you are looking for a quick video to watch, you might want to move along. The review is in nine videos ranging from an introduction, to a comparison of build quality, discussion about the displays on each meter, and, of course, the measurement capability of each meter. There’s even a video that shows tear downs so you can see inside the instruments.
Continue reading “$50 Multimeter Comparison and Teardown”
You can’t argue that Arduinos are extremely popular with the maker/hacker community. Some would say that there is certainly no shortage of projects to make using them. [Milen] thought otherwise and felt it was time to create an Arduino-based multimeter.
At the heart of this project is a common Arduino Uno. The additional parts were kept to a minimum in order to keep down the overall cost and project complexity. The finished product can measure voltage from 0-100v, amperage up to 500mA and resistance between 0-250 kohm. If you need to check for continuity, it can do that too.
All of the parts required to make the multimeter fit on a shield that plugs directly into the Arduino. Banana plugs allow for attaching test leads. The measurement values are displayed on an LCD screen and/or (if connected) to the Arduino IDE Serial Monitor. If only using the serial monitor, the LCD screen can be omitted to save a few bucks.
Continue reading “DIY Multimeter, Arduino Sold Seperately”
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]
[funnypolynomial] saw this Pong clock years ago and had been planning on building his own version. With a move looming he decided it was finally time to finish up his Pong clock since completed projects take far less room than incomplete ones. The core of the system is a ThinkPad. He separated the hinge and bolted the keyboard to the back of the screen. The display ribbon was long enough, but he had to extend the wires for the backlight. The power button was also extended and the battery removed. The software is a Windows screen saver that uses the two mouse buttons for navigation similar to how you set a two button watch. Every minute the the left player misses the ball and the right player’s score increases. You can see a video of the clock below. In the past, he also turned a digital multimeter into a clock. Continue reading “Pong clock”