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THE LOAD CELL AND STRAIN GAUGING SPECIALISTS

Definitions

Definition of Load Cell Specification Terms

  • Accuracy – Normally quoted as either a percentage of full scale output or a percentage of the applied load. The accuracy figure is the combined error caused by non linearity, repeatability and hysteresis error values in the load cell.
  • Rated Capacity – The maximum load over which the load cell which operate within its specifications.
  • Compensated Temperature Range – The range of temperatures over which the output from the cell is compensated. If used outside this range the output cannot be guaranteed to follow the specifications.
  • Environmental Protection – IP rating against moisture and dust e.g. IP65.
  • Excitation – The voltage applied to the Ex+ and Ex- wires, normally quoted as minimum and maximum values e.g. 5 to 15VDC or as a recommended value and maximum value.
  • Hysteresis – When a load cell is taken from zero to full load and back to zero the millivolt (mV) output for a given load value will be slightly different when the load is rising to when the load is falling. The maximum difference is used to calculate the hysteresis. Normally quoted as a percentage of full load.
  • Input Resistance – The resistance measured across S+ and S- with load cell disconnected and no load.
  • Output Resistance – The nominal resistance measured between Ex+ and Ex- with load cell disconnected and no load.
  • Insulation Resistance – Normally measured at 50VDC this is the minimum resistance between the metal body of the load cell and any of its electrical connections.
  • Mechanical Failure – The load at which the cell is likely to fail mechanically i.e. break or deform.
  • Rated Output – The nominal mV/V output of the load cell.
  • Repeatability – A measure of the ability of the load cell to repeatedly give the same output for the same load under the same conditions. The error is normally quoted as a percentage of full load.
  • Safe Overload – The amount by which the capacity of the cell can be exceeded e.g. 150% of capacity.
  • Temperature Effect On Span – Usually quoted as a percentage of full scale this is the change in output at full load due to temperature changes. e.g. 0.01 %/1 0°C means a change of up to 0.01% of full load output per temperature change of 10°C.
  • Temperature Effect On Zero – As above but measured at zero load.
  • Zero Balance – The output of the load cell at no load, normally quoted as a percentage of full load. Also know as zero offset.
  • Zero Return (Creep) – The difference between the mV output at zero before a load is applied and the mV output at zero when returning from being loaded (after being given time to stabilise). Normally quoted as a percentage of full load over a time period e.g. 0.03% (30 mins).