DC amp probe for O'scope to measure 100-400ma

Discussion in 'The Projects Forum' started by dick56, Apr 1, 2014.

  1. dick56

    Thread Starter New Member

    Apr 27, 2011
    23
    3
    I would like to build a probe that connects to my Fluke 97 o'scope that will measure small DC current. I will be measuring small DC motors on aircraft like fuel pumps and landing gear and flap motors. I want to establish a baseline scope tracing of each motor so I can come back in a year and reread and see if something is going fishy with the armature and or the brushes. There are lots of clamp-on DC probes in the marketplace, but the current I will be reading is in the 100ma to 400ma range.

    I see in the Completed Projects Forum there is a project for an AC probe for a digital multimeter, but I want to look at and store the current waveforms on the Fluke 97. A probe like the AC one seems simple enough to build so can a small current DC probe for a scope be as easy to build?

    Does anyone have a schematic they could pencil up with the needed components? Thanks for the help.
     
    Last edited: Apr 1, 2014
  2. crutschow

    Expert

    Mar 14, 2008
    13,000
    3,229
    DC probes are much more complicated. A simple coil of wire can detect an AC current but not DC. For that you need something to detect DC current such as a Hall-effect sensor. Perhaps one of these would work for you.
     
  3. dick56

    Thread Starter New Member

    Apr 27, 2011
    23
    3
    Zapper, thanks for the heads up. I would be hard pressed to make one for those numbers.
     
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