How to measure device output that is an "mA" output?

Discussion in 'The Projects Forum' started by MikeA, May 25, 2016.

  1. MikeA

    Thread Starter Member

    Jan 20, 2013
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    I have a device that has an analog output that I would like to measure it with a 5v Arduino. The output is rated 5-50mA.

    How would one go about measuring current? A resistor across the terminals and measure voltage across the resistor? Am I on the right track? :confused:
     
  2. Brevor

    Active Member

    Apr 9, 2011
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    54
    Yes, thats the way it's usually done. A 100 ohm resistor will have 5 Volts across it at 50 ma.
     
  3. MikeA

    Thread Starter Member

    Jan 20, 2013
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    17
    That's easy enough. :D

    Now I'm just curious why would some devices have voltage outs and some amps outs? What are the ups and downs of using one over the other?
     
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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  5. crutschow

    Expert

    Mar 14, 2008
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    What type of "devices" are you talking about.
     
  6. MikeA

    Thread Starter Member

    Jan 20, 2013
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    An HVAC environment monitor that might hang on a wall hundreds and hundreds of feet away from the main control panel.
     
  7. crutschow

    Expert

    Mar 14, 2008
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    For that a current-loop (commonly 4-20mA) is often used since it's less sensitive to noise pickup then a voltage signal.
    Also the same current can be used to provide power to the remote sensor, so two wires can provide both power and signal.
     
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