AD8215 current sensing

Discussion in 'The Projects Forum' started by TheNewGuy, Apr 4, 2013.

  1. TheNewGuy

    Thread Starter New Member

    Nov 16, 2012
    2
    0
    I am trying to use the AD8215 current sensing chip, but I am having trouble making it work. I connected it as it shows in the datasheet for high side sensing. I am currently trying to test it out using a power source from our lab. The power source goes from 0-20 volts and has a max current of .4 amps. The shunt resistor that I am using is .042 Ohms. After the sensing I continue my to complete the circuit loop with a 1k Ohm power resistor then back to ground.

    The datasheet says that the chip output with have the following equation.
    OUTPUT=(Ishunt*Rshunt)*20
    Using this eq. we are taking our output voltage and dividing it by (20*.042) which equals .84, so basically we get OUTPUT/.84 .

    When we take measurements we get
    INPUT Output from chip calculated Ishunt
    10 V 9.4 V 11.19A
    15 V 14.5 V 17.2A
    I know that these are amps are way higher than what my power source can give, but do not see where I am going wrong.
    Has anyone had similar issues with this chip. Could someone give me a point in the right direction? Does the amps have to be a certain level before the chip will work. The chip will be doing high side sensing. The input coming from a solar panel so the normal voltage will be around 28V and the current could be as high as 7 amps. I need to sense the current so that I can try to make a MPPT for the solar panel.
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,009
    3,233
    Are you sure the resistor is 0.042 ohms?
    Measure the voltage drop directly across the resistor to see if it's correct.
    Post a complete circuit diagram of your setup.
     
  3. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    Your amplifier is saturating at the positive rail. It sounds like your sense resistor is much too high, or even not connected. With a 1k load, you should be getting 16.8mV out.
     
Loading...