How to check a load cell and his converter

Considerations

  • The measurements in the conectors must be with the screws properly tightened, in this way we can assure a good connexion.
  • The load cell has 4 basic wires, 2 of them are for power supply (+Vexc y -Vexc) and the other two for the output signal.
  • The signal in mV, changes proportionally to the effort applied to the load cell and to his power supply.
    • E.g a 2mV sensitivity cell with 10V in Vexc, will give you 20mV for an effort equivalent to his scale.

How to check it

1.- Check that the auxiliar supply of the converter is the correct one, 24VDC, 230VAC

2.-Connect the power wires to the load cell to the correct connectors of the converter (+Vexc and -Vexc), leaving the output wires(+Vsignal y -Vsignal) without connecting to the converter.

  • Measure the input voltage of the cell it should be about constant 10VDC.
    • If there’s no power, or it’s variable, or unstable, the module is broken.
  • Measure the mV signal in the output wires without connecting (+Vsignal and -Vsignal), this signal should be proportional to the effort in the load cell, so the mV should change with the effort.
    • If the mV doesn’t change cell is broken.
    • The cell without load should give a 0mV signal, to compensate it adjust with the ZERO adjustable.
  • Connect the 4 wires of the cell to the converter, if the supply and the cell signal are the porper ones.
    • Respect the polarity, a negative signal , it may display ” 0 ” in the output , pretending it does not work

3.- Measure the corresponding output with a multimeter. It should be proportional to the effort in the input.

  • If the output is in the maximun and it doesn’t correspond with the input signal, the converter is broken.
  • If the output gives a “0”, check the connexions of the load cell, the polarity could be inverted.

Here  you can find different kind of adders for load cells, converters, load limiters for cranes, power supplies, load sim. and load cells.