Load Cell Frequently Asked Questions
Load Cell Sensitivity+
Typical unamplified analog load cells have a sensitivity rating with a unit of mV/V. This rating is specified on a load cell data sheet often in the 1mV/V - 3mV/V range. Most quality load cells will come with a factory calibration sheet which specifies the actual sensitivity rating for each individual load cell produced. This sensitivity value can be used to convert the load cell's output to scientific units of weight or force.
Convert Load Cell Voltage to Pounds or Kilograms or Newtons+
As mentioned above, each load cell should come with a calibration certificate denoting the sensitivity for each individual cell. This value can be used to convert the load cell's output signal to usable units of weight or force. To calculate the output voltage of the cell relative to the full load on the cell, use the following equation: S*Ve. Where S = sensitivity (mV/V), Ve = excitation voltage (V). Naturally, if we were to convert this output voltage to force/weight, we could use S*Ve/Ctot. Where Ctot = total rated capacity of the load cell (Kg or Lb or N).
If the load cell is not factory calibrated, it must be field calibrated to determine the sensitivity. To do so, record the no-load output value, then load the cell with a known load and record the output. Subtract the zero output voltage and use the resulting voltage as the calibration factor: S = Ctot(Vl-V0)/(Ve*Load). Where V0 = unloaded output voltage, Vl = loaded output voltage, Ve = excitation voltage, Load = known load, and Ctot is the total rated capacity of the cell.