Zero Resistance Amp meter (ZRA)

vortexflowvortexflow Posts: 2
I am looking for an easy way to measure milliamp current using a zero resistance method ( no Shunt).
Anybody have any idea where to look or start?


  • 9 Comments sorted by Date Added Votes
  • BeanBean Posts: 7,824
    edited February 2009 Vote Up0Vote Down
    Use a hall effect type current sensor.
    These are a ring that you run the wire through. It senses the magnetic field generated by the current flowing through the wire.


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  • SRLMSRLM Posts: 5,044
    edited February 2009 Vote Up0Vote Down
    A forum member had a bunch of current meters for sale recently, he may still have some. I'm not sure if they match your specs, but if you do some searching you may find the thread.
  • vortexflowvortexflow Posts: 2
    edited February 2009 Vote Up0Vote Down
    I am not sure if a hall sensor is sensitive enough for what i am trying to accomplish. The only method i know off is using a combo of Op Amp and am ADC in a feed back loop. Also, I was reading somewhere that you can take advantage of the Basic stamp internal function to measure low current without a shunt. Unfortunately, there is not much out there to give specifics on either method.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited February 2009 Vote Up0Vote Down
    Moving from BASIC Stamps to Sesnros forum...

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  • BradCBradC Posts: 2,601
    edited February 2009 Vote Up0Vote Down
    vortexflow said...
    I am not sure if a hall sensor is sensitive enough for what i am trying to accomplish.

    Wrap the wire several times through a ferrite core with a slot cut in it. Insert the Hall Effect into the slot in the core to measure the field.

    Wrap the wire as many times as you need to get the sensitivity you need.

    Of course this is only any good if you are not worried about suppressing or interfering with AC in the wire, but it works well for very low speed or DC.

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  • RickBRickB Posts: 385
    edited February 2009 Vote Up0Vote Down
    The input to an inverting op amp is a virtual ground. Fluke uses this technique to create a lossless (zero burden) current to voltage converter for one of their 6.5 digit meters on the 20 and 200 uA ranges. You might try making a power transistor input/output op amp to see if this technique will work at higher currents.


    Correction!!! 6.5 digits

    Post Edited (RickB) : 3/4/2009 6:59:05 AM GMT
  • datsun2literdatsun2liter Posts: 5
    edited March 2009 Vote Up0Vote Down
    Similar question, I'm using a Energy Detective to measure household energy use. I'd like to monitor individual circuits in the house main panel. A Propeller would have enough inputs to monitor all the important stuff. If I put a coil of wire around each "hot" wire, how can i measure current with a basic stamp? Once you standardize the coils you could see how much power each line is using.
  • FranklinFranklin Posts: 4,747
    edited March 2009 Vote Up0Vote Down
    These kinds of devices are designed to measure current. [noparse][[/noparse]url[noparse][[/noparse]

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