Give Your Multimeter A Wireless Remote Display

Multimeters are one of the key tools in a hardware hacker’s bench. For 90% of us, the meter leads are perfect for making measurements and looking over at the results. Sometimes you need a bit more distance though, and for that, [Ken Kaarvik] has created the Multimeter remote display. Remote displays are pretty handy when you want to measure something several feet away from your bench. They’re also great if you need to check something in an enclosed space, like a server rack or a refrigerator. Fluke actually sells multimeters with wireless displays, such as their model 233.

The key to this project is the FS9721 LP3 chip by Fortune Semiconductor. (PDF link) The FS9721 is essentially a system on chip (SOC) for multimeters. It contains a digital to analog to digital converter, an LCD driver, and a microcontroller. It also can send data out over a 2400 baud serial link. Two of [Ken’s] multimeters, the Digitek DT-4000ZC and a Fluke 17B, both have this chip. The Digitek has a 1/8″ plug for connecting to the outside world, while the Fluke requires some simple hardware mods to enable data output.

Since this was his entry for the Trinket EDC contest,  [Ken] connected the serial output of the FS9721 to an Adafruit Pro Trinket. The Trinket formats the data and sends it to an  nRF24L01+ 2.4GHz radio module. The receiving end has an identical radio, and another Pro Trinket. [Ken] actually built two wireless displays. One is a dual-boot Game Boy advance which has a really slick background on the color display. The other receiver utilizes a 128×64 OLED. The trinket, nRF24L01+ and display all fit neatly inside an Altoids tin.

Click past the break to see both wireless remote displays in action!

27 thoughts on “Give Your Multimeter A Wireless Remote Display

  1. This got me to thinking about the bluetooth meters that have been mentioned here so I did a quick search and found this meter the TekPower TP9605BT Multimeter. It is only sold by one source but cost only $79.00 usd with shipping. Here are the specs; Full Function 6000 Counts True RMS Multimeter with Intelligent Connections, Bluetooth Cellphone Connected Multimeter ( Android Only Now), USB connected multimeter, Comes with K-Type Thermo sensor and Optical USB Cable, Free APP software and USB Data logger software. It seems to be so new I am unable to find any reviews. I did purchase one to play with and see how “hackable” it might be.

  2. “They’re also great if you need to check something in an enclosed space, like a server rack or a refrigerator.”

    In a server rack, maybe, but not for sure. It depends of the rack. Inside a fridge, definitely not, because the fridge case is metallic, and it will act as a Faraday cage.

    1. Fridges aren’t designed to be Faraday cages. They will attenuate the signal somewhat, but you you’ll have no problem getting a signal through them. Put your cell phone in the fridge and you’ll have no problem calling it (Yes, I just tried this myself – and am getting strange looks from my wife)

      1. Indeed, my phone too was ringing just fine inside my fridge. I was wrong about the fridge acting as Faraday cage.
        You made me laugh to tears picturing that last sentence of yours. Sorry for getting you into trouble!

  3. Perhaps I don’t have a good enough imagination, but I can’t imagine ANY scenario that I would need the testing part (i.e. the leads) at one place, and the display readout at another. Can’t reach from the bench equipment to the experiment – use a handheld meter. Testing points are buried inside the experiment, use longer leads. Feel free to expand my horizons.

    1. First off, I accidentally clicked Report Comment on your comment. Sorry! I meant to hit reply.

      “I’m turning the key, but the car isn’t starting. Is it even drawing power? I’ll just put my remote volt meter on the battery, and put the screen in the cab while I crank it.”

    2. I have this scenario frequently. I work as a licensed passenger elevator mechanic and this happens often. I usually have to get a second person to read and phone measurements or results and getting help is not often convenient. The controller is in a remote location and the elevator is moving somewhere else. Or I am metering something in the car and I am located on top of the car. Or like have been fighting this week, i am in the machine room and the selector control cabinet is in one location and the front of the controller with relays I need to verify operation/voltages is 20 feet away and on opposite facing side to not miss the result. I literally have had to place calls on selector relays and RUN around to front of controller to not miss the event lasting about 5 seconds. I ordered a meter with phone app and still considering buying the Fluke 233.

  4. I’m not sure that I would use the wireless functionality of a dmm enough to warrant the extra cost, but what I’d like is to have the ability to have the reading spoken to me. To be able to get the measurement without looking away from the probes would be nice in tight spots.

  5. I have several fluke 233s – they are mostly junk as they eat batteries like crazy, even when they are “off” as the display is always pinging the measurement half.

    I assume it goes into to some sort of low voltage, only check in every once in a while type of mode when off, but they sure love the batteries.

    Nothing like pushing my tool cart across the building for a job and pulling a meter out just to find that it’s dead, and all it’s friends are dead too. I only have so much room on there for spare batteries.

    My 287, while largeish and heavy, has way more functions and a nice large screen and doesn’t go through near as many batteries. I tend to use it more often.

    The 233s are nice for floating up inside a cabinet. I don’t think HV has ever glitched one out that I’ve noticed… yet.

  6. Might mod my DT-991-4 as though it does not have a serial port I can probably find the relevant pins.
    Reporting current rotary switch position isn’t quite as simple but still doable.

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