Connect with us

DIY wallwart-powered DMM?

Discussion in 'General Electronics Discussion' started by moeburn, Aug 6, 2013.

Scroll to continue with content
  1. moeburn


    Jun 25, 2012
    Since the accuracy of my DMM is so dependent on the battery voltage, and it takes 3 AAAs, which tend to be hard to come by in this house, would it be as simple as getting a 4.5v wall wart DC transformer with a decent current rating and wiring it to the battery leads, so I can stop relying on battery voltage? Or would the ripple in the rectified voltage affect the accuracy of the DMM?
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    1) Who says it is "so dependant on battery voltage"?

    2) If you use an external power source you need to be aware that your measurements are no longer completely isolated.

    3) The circuit will have been designed knowing the supply has no ripple, so any ripple on the supply *may* have unintended effects.

    I have a meter which starts to read incorrectly when the batteries go flat, but it only happens when they are quite flat.

    I would get a good brand of AAA cells. They'll probably last a lot longer and be less prone to leakage. I can't tell you how many things I have had damaged due to cheap batteries...
    hevans1944 likes this.
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day