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.
Continue reading “Amp Volt Ohm Meter Model 8 Mark III From The 1960s”
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.
Continue reading “This Servo Actuated Multimeter Does The Twist”
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.
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.
Continue reading “Is That Cheap Multimeter As Good As A Fluke? Let’s Find Out”
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.
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.
Continue reading “The True Cost Of Multimeters”
For his Hackaday Prize entry, [Martin] is building an Open Source Multimeter that can measure voltage, current, and power. It’s an amazing build, and you too can build one yourself.
The features for this multimeter consist of voltage mode with a range of +/-6V and +/-60V. There’s a current mode, basically the same as voltage, with a range of +/-60 mA and +/-500mA. Unlike our bright yellow Fluke, there’s also a power mode that measures voltage and current at the same time, with all four combinations of ranges available. There’s a continuity test that sounds a buzzer when the resistance is below 50 Ω, and a component test mode that measures resistors, caps, and diodes. There’s a fully isolated USB interface capable of receiving commands and transmitting data, a real-time clock, and in the future there might be frequency measurement.
This build is based on the STM32F103 microcontroller, uses an old Nokia phone screen, and unlike so many other multimeters, this thing is small. It’s very small. More than small enough to fit in your pocket and forget about it, unlike nearly every other multimeter available. There’s one thing about multimeters, and it’s that the best multimeter is the one that you have in your hands when you need it, and this one certainly fits the bill.
The entire project is being written up on hackaday.io, there’s a GitHub repo for all the hardware and software, and there’s also a video demo covering all the features (available below). This is a stand-out project, and something we desperately want to get our hands on.
Continue reading “Finally, An Open Source Multimeter”