PCB a Week 9: MrRef voltage and current reference update

in PCBs by DP | 5 comments

MrRef1

Mats posted pictures of his MrRef voltage and current reference PCB build.  This tool helps check the accuracy of your multimeter:

Since my Agilent 34401 is currently out of calibration I didn’t bother installing the fine-adjustment trimopot. The 6350 is good for 0.02% (1mV) without any adjustments. But I installed two 10K 0.05% resistors on the board to get the 1mA output working.

The idea of using two cr1216 in each battery holder kinda works (I need >8 volts to run the chip so I have now four 3v cells in series), but the next revision of the board will use four separate battery holders. It’s too easy to short out the two positive poles of the batteries in the holder, I had to insulate them with kapton tape to get it working properly.

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Comments

  1. Oliver says:

    shut up and take my money!

    Really, I really like this idea. Having some ‘guaranteed’ reference to verify equipment against is awesome. A little more to ‘finish the edges’, like you said the battery holders etc. But if not too expensive (and it really shouldn’t be, as the only real costs are the chip) this should be available at seeed or the like.

  2. Drone says:

    This looks like it is missing one thing – a 0.1″ header and jumper to disconnect the batteries? After-all, you use a device like this infrequently and removing the batteries between uses will be a PTH. Of-course I may be missing something; I haven’t drilled down into the design (if-true, sorry for that).

    • Mats Engstrom (@matseng) says:

      There’s a nice smd slide switch just below the green led…. It turns the device on and off . :-)

      • Drone says:

        Aha! That is great. It should be a prominent feature IMHO. Thanks for the clarification.

  3. David says:

    I bought the DMMCHECK Plus, it does a lot more at:
    http://www.voltagestandard.com/DMMCheck_Plus.html
    Heard about it from David L. Jones – EEVBlog

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