multimeter

86 Articles

The Swiss Army Knife Of Bench Tools

July 28, 2020 by 20 Comments

[splat238] had a ton of spare sensors laying around that he had either bought for a separate project or on an impulse buy, so he knew he had to do something with them. He decided to build his own digital multi-tool focusing on sensors that would be particularly useful in a workshop setting. Coincidentally, he was inspired by a previous hack that we covered a while back.

He’s equipped his device with a bubble level, tachometer, IR thermometer, protractor, laser pointer, and many, many more features that would make great additions to any hacker’s workspace. There’s a good summary of each sensor, making his Instructable somewhat of a quick guide to common sensing modalities for hardware designers. The tachometer, thermometer, laser pointer, and a few other capabilities are notable upgrades from the project we highlighted previously. We also appreciate the bigger display, allowing for more detailed user feedback particularly in using the compass and bullseye digital level among other features.

The number of components in [splat238’s] build is too extensive to detail one-by-one in this article, so please see his Instructable linked above for all the details. [splat238] made his own PCB for mounting each sensor and did a good job making the design modular so you wouldn’t need to add certain components if you don’t need them. Most of the components take some through-hole soldering with only a handful of 0805 resistors required otherwise. The housing was designed such that the user can handle the tool with one hand and can switch between each function with a push of a button.

Finally, the device is powered using a rechargeable lithium-polymer battery making it very reusable. And, if there weren’t enough features already, the battery can be charged via USB or through two solar panels mounted into the housing unit. Okay, solar charging might be a case of featuritis, but still a cool build either way.

Check out some other handy DIY tools on Hackaday.

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Amp Volt Ohm Meter Model 8 Mark III From The 1960s

February 16, 2020 by 22 Comments

There’s hardly any piece of test equipment more fundamental than a volt ohm meter. Today you’re likely to have a digital one, but for most of history, these devices had real needle meters. The AVOmeter Model 8 Mark III that [Jeff Tranter] shows off had an odd banana-shaped meter. Maybe that goes with the banana plugs. You can get a closer view of this vintage piece of equipment in the video after the break.

Even the outside description of the meter is interesting. There were several unique features. For example, if the meter goes full scale a little button pops out and disconnects the probes to protect the meter. Another unusual control reversed the polarity of the leads so you didn’t have to swap them manually.

Some of the other features will be familiar to anyone who has used a good analog meter. For example, the meter movement has a mirror under the needle. This is used to make sure you are looking straight down on the needle when making readings. If you can see the reflection of the needle, then you are off to one side and will not read the precise value you are interested in.

If you only want to see the insides, [Jeff] teases you until around the six minute mark. There are no active devices and this meter is old enough to not use a printed circuit board. The AC ranges work with a transformer and germanium diodes. The rest of the circuit is mostly a bunch of resistors.

The point to point wiring always makes us wonder who built this thing sixty years ago. You can only wonder what they would think if they knew we were looking at their handiwork in the year 2020.

We see a lot of meter clocks, but it would be a shame to tear this unique meter apart for its movement. Perhaps someone should make a clock that outputs a voltage to a terminal so you could read it with your favorite meter. This instrument was probably pretty precise for its day, but we doubt it can match a modern 6.5 digit digital instrument.

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This Servo Actuated Multimeter Does The Twist

February 14, 2020 by 9 Comments

This tip comes our way courtesy of [Elad Orbach], who’s been experimenting with a device that uses a servo to turn the function dial on a multimeter. It’s something you can put together in a few minutes with leftovers from the parts bin, and as you can see in the video after the break, the basic concept seems to be sound enough.

As to finding a practical reason for spinning the switch on your meter with a servo, that’s left largely as an exercise for the reader. [Elad] hints at the possibility of using such a setup to help automate repetitive testing, which we could see being useful especially in combination with a foot pedal that allows you to switch modes without having to put the probes down. The same basic idea could also be helpful as an assistive device for those who have difficulty grasping or limited dexterity.

Whether top of the line or bottom of the barrel, the multimeter is easily the hardware hacker’s most frequently used tool (beyond the screwdriver, perhaps). We’ve seen plenty of projects that try to graft additional features onto this common gadgets, though automation isn’t usually among them.

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’75 Nixie Multimeter As Digital Dice

January 20, 2020 by 10 Comments

For the casual Monopoly or Risk player, using plain six-sided dice is probably fine. For other games you may need dice with much more than six sides, and if you really want to go overboard you can do what [John] did and build electronic dice with a random number generator if you really need to remove the pesky practice of rolling physical dice during your games of chance.

The “digital dice” he built are based on a multimeter from 1975 which has some hardware in it that was worth preserving, including a high quality set of nixie tubes. Nixies can be a little hard to come by these days, but are interesting pieces of hardware in their own right. [John] added some modern hardware to it as well, including an AVR microcontroller that handles the (pseudo) random number generation. A hardware switch tells the microcontroller how many sides the “die” to be emulated will need, and then a button generates the result of the roll.

This is a pretty great use for an old piece of hardware which would otherwise be obsolete by now. [John] considers this a “Resto-Mod” and the finish and quality of the build almost makes it look all original. It’s certainly a conversation piece at the D&D sessions he frequents.

Is That Cheap Multimeter As Good As A Fluke? Let’s Find Out

December 22, 2019 by 68 Comments

When [learnelectronics] talks about cheap meters, he always says, “If you are doing this for a living, get yourself a Fluke.” But he realized he’s never shown the inside of a Fluke meter, so he rectified that in his most recent post. For comparison, he opens up a Fluke 26-III and an Aneng AN870 (retailing at about $500 and $30, respectively).

The initial opening shows that the Fluke has hefty brand name fuses, but the Aneng has little generic fuses. In addition, the Fluke has an internal case that helps keep you away from live voltage. The Fluke also has a proper rotary switch, while the cheap meter has a switch that is etched on the PC board; a cost-cutting trick that’s often a point of failure on these cheap meters.

The Fluke also has a significantly larger number of protection devices and heftier components, you presume can take more punishment. Of course, if you don’t have a few hundred volts running through your meter, it probably doesn’t matter. The cheap meters are certainly good enough, even though you do get what you pay for, as you might expect.

As long as you have a meter open, you might as well hack it to have WiFi. Or, if you prefer, a serial port.

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Multimeter Display Perked Up With Nixies, LEDs, And Neon Tubes

October 30, 2019 by 6 Comments

Just because something is newer than something else doesn’t automatically make it better. Of course the opposite is also true, but when it comes to displays on bench multimeters, a fancy LCD display is no guarantee of legibility. Take the Hewlett Packard HP 3478A multimeter; the stock transflective display with its 14-segment characters is so hard to read that people usually have to add a backlight to use it.

That wasn’t good enough for [cyclotronboy], though, who chose to completely replace the stock 3478A display with Nixie tubes. He noticed that with a little modification, six IN-17 tubes just fit in the window vacated by the LCD. He sniffed out the serial data stream going to the display with a collection of XOR gates and flip-flops, which let him write the code for a PIC18F4550. The finished display adds a trio of rectangular LEDs for the + and – indicators, and an HDLO-1414 four-character alphanumeric display to indicate units and the like. And the decimal points? Tiny neon bulbs. It already looks miles better than the stock display, and with the addition of a red filter, it should look even better.

If you’re stuck with a lame LCD multimeter but Nixies don’t quite do it for you, worry not – an LED conversion is possible too.

The True Cost Of Multimeters

October 18, 2019 by 70 Comments

If you are building a home shop, it is common to try to get the cheapest gear you can possibly get. However, professionals often look at TCO or total cost of ownership. Buying a cheap car, for example, can cost more in the long run compared to buying an expensive car that requires less maintenance. Most consumers will nod sagely and think of ink jet printers. That $20 printer with the $80 cartridges might not be such a deal after all. [JohnAudioTech] bought a few cheap multimeters and now has problems with each of them. Maybe that $120 meter isn’t such a bad deal, after all.

The problems he’s seen are the same ones we’ve all seen: noisy selector switches, suspect display readings, and worn off lettering. You can see the whole story in the video below.

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