Difference load cell & strain gauge / Basic question of strain

Discussion in 'General Electronics Chat' started by aamirali, Mar 25, 2014.

  1. aamirali

    Thread Starter Member

    Feb 2, 2012
    415
    1
    Is there any difference between strain gauge & load cell.

    Load cell datasheet: http://www.meas-spec.com/downloads/FC23.pdf

    strain data: http://www.omega.com/techref/pdf/STRAIN_GAGE_TECHNICAL_DATA.pdf


    If we look at datsheet of load cell it exactly says that at full rated load voltage will be 100mV. Full rated load is given exactly.

    1. Strain gauge datasheet mentions only strain like 50000 micrstrain. How can I convert it into weight. What's is the weight when strain is 5000, 10000, microstrian. What is max weight in kg when 50000 microstrain occurs.

    2. When we connect strain gauge in quarter bridge it gives output in change in voltage when strain gauge resistance change. Let say on 1 ohm change voltage change to 1mV. Now how to convert it into load in microcontroller code.
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,446
    3,361
    A strain gauge is a single resistive element.

    A load cell is an arrangement of four strain gauges in a Wheatstone bridge arrangement.

    To use a load cell you apply a voltage to opposite nodes of the bridge and measure the voltage from the other opposite nodes.

    To use a strain gauge properly you would arrange two or four strain gauges so as to experience opposite forces. For example, one gauge can be mounted on the top side of a cantilever while another gauge is on the bottom side of the cantilever.

    You would still apply a voltage to the stain gauge bridge arrangement and measure voltage. Four strain gauges are required for temperature compensation.
     
  3. aamirali

    Thread Starter Member

    Feb 2, 2012
    415
    1
    Thanks for your reply.
    Can you answer my other two questions on how to calculate Kg of weight from voltage generated.

    Given srain gauge is 1000 ohm unstrained , gauge factor = 2 , max strain = 50000ue
     
  4. MrChips

    Moderator

    Oct 2, 2009
    12,446
    3,361
    It would depend on the physical arrangement of the strain gauge and the applied voltage.
    The simplest solution is to build and test it and then calibrated it with a known weight.
     
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