4-20 mA to RPM calculation

Discussion in 'The Projects Forum' started by vijay s, Apr 1, 2010.

  1. vijay s

    Thread Starter New Member

    Jun 20, 2008
    Hai Folks
    i need little clarity.. i am using 4-20 mA curren loop Transmitter for RPM Measurement.. The Transmitter has a Frequency Range of 0.0005Hz to 50KHZ... i have 250ohm Resistor connected to a current loop.. which intend produce Voltage of 1-5V.. i Got confusion with calculating this to Frequency..
    Please i need help on this....
  2. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    Subtract 4mA or 1V to make the result zero based.

    That makes the scale 0 - 4V for 0 - 50KHz.

    Example, 2.2V /4 *50 = 27.5 KHz

    Add the 1V back, so 3.2V across the 250 Ohms is 27.5 KHz