Current measuring

Discussion in 'General Electronics Chat' started by ajitnayak, Sep 12, 2014.

  1. ajitnayak

    Thread Starter Member

    Feb 22, 2013
    Dear all,

    I am trying to build string monitoring current of solar application. we have 24 string . Bus bar can carry the voltage 1000v,25A. Now i am trying to build current through each string. There are 2 ways of doing it

    1) Hall effect based current sensor
    2)RShunt based current measurement.

    I need help guideline for this project.
    technique 1: pass the string through each hall sensor and measure through controller and Displayed via modbus. My sensor cost me around 300RS and price work out to be 7200Rs(Sensors)+(2k-3k) PCB/controller/voltage trasducer/enclosure/etc.
    technique 2: If use Rsh basis use of shunt resistor, filtering circuits,sognal conditioning, sampling,controlling ,etc cost work out to be 8000RS.

    Now my problem Since we measuring current not frequent basis. We measure current for Say 30min or 1 hour.Is there any way i can bring my cost down.
    Only hardware cost is more.How can bring cost down. any other way to bring it down
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
    you should measure each string of pv, not at the buss bar, but where the string connects to the bar. measuring the buss bar current at multiple places will limit the resolution of your measurements the farther you go.
  3. wayneh


    Sep 9, 2010
    You could probably save a little by multiplexing the sensors and sampling them one at a time, since you do not need a high sample rate.
  4. ajitnayak

    Thread Starter Member

    Feb 22, 2013
    that i know. That reason i am using hall sensor for each sting. But inorder to save cost . My question is is it possible to switch string via hardware so that with 1 hall sensor i can switch between strings and measure current
  5. wayneh


    Sep 9, 2010
    You want to isolate the current from one PV string while all strings remain "live"? Is it possible to pass conductors from all strings through the sensor AND around the sensor? This would allow MOSFET switching to divert just one string at a time onto the conductor passing the sensor.

    But it might be cheaper to just put a sensor on each string and multiplex them.
  6. cmartinez

    AAC Fanatic!

    Jan 17, 2007
  7. NorthGuy

    Active Member

    Jun 28, 2014
    24 strings produce 1000V and 25A, which means a single string produces 1000V and 1A. This doesn't sound right. Are you sure you have 24 strings? With regularly sized panels, to get 1000V and 25A, you would have about 3 strings consisting of about 25 panels each.
  8. Cal Rico

    New Member

    May 1, 2012
    for 1000v,25A. this is solar powering a home or building right? go to Martin Lorton YouTube channel. His early videos discusses solar paneling as he had built several system in his South Africa homes. Apparently he is now living in Ohio, USA, and again will be embarking upon solar powering this new house.
    If you have difficulty finding his YouTube channel, just go to Dave Jones EEVBlog link above, and you will Dave has a link to Martin.

    Be patient in watching. If you email him, He tries really hard to respond promptly