1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

CURRENT LOOP Q. i HAVE ATTEMPTED, JUST NEED CORRECTION OR REJECTION . THANKS

  1. Mar 16, 2010 #1
    1. The problem statement, all variables and given/known data

    A 4-20mA current loop is being used to transfer temperature
    values in the range + 10ºC to +60ºC.
    (i) What temperature is represented by a current of 7mA?
    (A) What current would you expect when the temperature of the
    sensor is 32ºC?

    2. Relevant equations
    i HAD AN ATTEMPT, CAN U TELL ME IF ITS RIGHT. I AM REALLY STRESSED OVER THIS QUESTION. THIS IS MY 3RD ATTEMPT. tHANKS FOLKS


    3. The attempt at a solution
    20-4 =16mA
    60-10= 50 DEGRESS

    50/16=3.125

    (A)
    7mA-

    3.125=X/7
    X=21.88 DEGREES

    (B)
    32 DEGREES-

    3.125=32/X

    X=32/3.125

    =10.24A
     
  2. jcsd
  3. Mar 16, 2010 #2

    Mark44

    Staff: Mentor

    This is correct, but don't forget units. When you divide degrees by milliamps, what's the unit you get?
    I get a smaller value. For each 3.125 degree increment above 10 degrees, you need to add another mA to 4 mA.
    Your units are wrong, and the value is too small, by my calculations.

    It would probably be helpful to derive one conversion formula for converting current in mA to temperature in degrees Celsius, and another to go the other way. The formulas you are using don't take into account that neither scale starts at 0.

    See if you can get the equation of the line through these two points: (10 deg, 4 mA), (60 deg, 20 mA).
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: CURRENT LOOP Q. i HAVE ATTEMPTED, JUST NEED CORRECTION OR REJECTION . THANKS
Loading...