shunt resistor

Discussion in 'General Electronics Chat' started by mlkcampion, Mar 14, 2007.

  1. mlkcampion

    Thread Starter Active Member

    Nov 16, 2006
    59
    0
    The circuit i have consists of one circuit which can carry anything up to
    50Adc at 12vDC. A shunt resistor (60mV = 100A) is placed in series with this
    circuit and thus produces a voltage drop between 0mV and 60mV depending on the current. Iam tyring to read this voltage into a PLC and i have placed an
    op-amp circuit giving me a gain of 50. This op-amp circuit is supplied via a 24vDC supply and i have commoned the two power supplies. My problem is when i measure the voltage across the shunt i get for example 10mV however when i measure across the 4.7uf capacitor (see circuit) i end up getting something like 16mV. What i dont understand is that the + and - of the shunt and the + and - of the capcitor are effectively the same points in the circuit?

    With the mV signal i would have expected a voltage drop due to maybe the wiring which i've shortened as much as i can but there still seems to be this error? if anyone knows of another way of acheiving the same thing with the shunt i would appreciate it?

    Thanks
     
  2. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,159
    MLKCampion,

    It looks like you didn't ground the input properly.
     
  3. mlkcampion

    Thread Starter Active Member

    Nov 16, 2006
    59
    0
    When i tried to download the .pdf file you attached it came up
    with a corrupt error.

    Thanks
     
  4. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,159
    try a right mouse....save target as....

    If that don't work, I'll post the three graphics
     
  5. mlkcampion

    Thread Starter Active Member

    Nov 16, 2006
    59
    0
    Hey Joe
    Yea i've tried that but it still wont open. I just check the picture that i attached, can you please note that i actually have a ground (pspice ground) to the left of the picture, i just noiced that i cut it out by accident.

    Thanks
     
  6. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
    144
    Strange, you should be able to either open or download the file. You haven't got file downloads disabled have you? If not can you screenshot the corruption error?

    Dave
     
  7. mlkcampion

    Thread Starter Active Member

    Nov 16, 2006
    59
    0
    No i dont, it downloads ok, just opening is the problem
     
  8. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
    144
    Then it must be an issue with your PDF reader. I would suggest you update to the latest version; if you're using Adobe Reader update to version 7.0.9 - I can confirm it opens fine with version 7.0.9 - or version 8.

    Dave
     
  9. mlkcampion

    Thread Starter Active Member

    Nov 16, 2006
    59
    0
    I've upgraded to 7.0.9 and i still get the same error. I s there another
    way you could post it?

    Thanks
     
  10. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Let's try this:

    jj-1.jpg

    jj2.jpg

    jj-3.jpg
     
  11. mlkcampion

    Thread Starter Active Member

    Nov 16, 2006
    59
    0
    Hey
    Thanks for that,
    i was able to download these. I ran a few more simulations and even
    though got slightly different results, i kinda get what you were sayin bout the
    ground. I am still working on the problem because simulating is one thing but trying to find the problem on the physical wiring ain't shown up much.

    Thanks
     
Loading...