Open hardware multimeter concept

EEVblog has a video about DIY multimeters. A few months ago the EEVblog forum talked about designing their own multimeter, so Dave made a video about his ideas on the subject.

We’ve also toyed with the idea of an open source digital multimeter, but ready-made devices are so cheap and ubiquitous it hasn’t become a priority.

Thanks Voidptr! Via the forum.

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12 Comments

  1. I for one would really like to know the circuitry wizardry behind the autoranging voltmeters. I have so many applications where its useful to have a auto gain control type thing.

    1. In the digital domain, you can start with high gain and check to see if your ADC is railed, change the gain to your PGA on the front end, then check again. In the analog domain, I imagine you could probably do something similar with a comparator – that way you wouldn’t even need an ADC.

      You should start a topic in the forum and see what ideas pop up!

  2. Dave has also been video blogging about a MCU controlled lab power supply design recently that might be worthy of a project/product. I’d love to purchase something like the Rigol DP1308A, but after blowing my entire annual budget on an brand new Agilent 3014A scope it will have to wait a while…. and I won’t have the patience to build one myself.

  3. Well, if it has some nifty features missing in commercial models, it might be worse to go.
    However, at the moment I could not think of any option I miss.
    Most likely, if you start to think about and try to add new features, you end up with an DSO with an integrated function generator.

    Well, just thinking, I think a modular system might be nice, take the upper part with the displays and the uC and allow to attach measurement modules for different purpose (the analogue part). Thus, you could have ultra-sensitive current readings (200A. Modules for thermocouples, capacitance, inductance, energy consumption, component testers, etc. Just provide a open and well documented interface, the base unit and a generic module for the standard tasks, and leave it to the community to come up with more modules.

    Storing to a SDcard and bluetooth or wifi connection to a PC might be interesting too.

  4. I need a multimeter – mostly voltage – that connects to a PC (via USB) and that gives me access to the current reading so that I can store the data myself and write my own user interface. The voltages need to go to 240 V approximately.
    That’s why I looked under open source.
    Can you offer me any guidance?

    Thanking you in advance.

    Alan

  5. Alan, There are many reasonably low cost multimeters with USB interfaces on the market. As far as I know most (all?) have a simple to use protocols. If you’re dealing with utility level voltages, a multimeter is probably a good idea as it will electrically isolate your equipment. The down side is that a battery operated device will operate for only a few hours. Just did a quick search on Deal Extreme and found this model : MS8226T at about $50. I think you can do even better pricewise… but I’d look for reviews before making a purchase.

    1. Correction: the Mastech MS8250C is USB, the one I mentioned above (MS8226T) is RS232 with is a big pain for most people these days.

      1. appreciate the prompt response, Joe. But here’s the problem. I need to have access to the data buffer. The spec sheet, which I downloaded, specifies that there’s a USB connection. That’s a great start. The challenge has been that the vendor writes an interface that doesn’t give access to the data in real time. Only after closing the application does data get stored – and only then can I access it.

        What I want is that each time I have a reading on the USB I can capture that point and decide how to process it. For example, I want to store it immediately (perhaps share the data with another application) and plot it in my own way.

        I need access to the real-time data.

        Can you please reconsider my problem in that light, Joe?

      2. just replied, but because there was a link in it, it went to the moderator for approval. I was saying basically these multimeters present them selves as a serial port device when connected to a computer and usually transmit data in a easy to understand text format. You don’t need to use their software (which is usually crap anyway). So you can read with whatever your favorite computer language in real time (ok there maybe a small lag, but well under 1s).

  6. Ya, I’d never use the Windows crudware that comes with these things. In most (all?) cases the devices presents itself as a serial port and it will stream data at the same rate that the display updates. At least that’s how my multimeters work. So there may be a lag of about half a second … but no more. So if you are using a Linux device, it will be matter of opening a device like /dev/ttyUSB0 and reading it like a file. Or you could use a short script (like this one I wrote: http://jdesbonnet.blogspot.ie/2011/12/time-tagging-data-streams-using-short.html ) to save it to a file with time information.

  7. We’ve been working on a multimeter that has many of the ideas talked about here including:

    – Two channel sampling (voltage-current or high voltage-low voltage)
    – BLE connection to smartphone or PC
    – SD card logging
    – App with time-graphs and XY plots on smartphone
    – Open BLE interface so people can write their apps, PC applications, etc.

    Check it out:
    moosh.im/mooshimeter
    Or support the project:
    http://www.dragoninnovation.com/projects/34-mooshimeter

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