It is an outline of the procedure and methods for calibrating load cells. 

Calibrations may use deadweight or hydraulic test equipment.

Methods to determine uncertainty of the test results and local specific gravity.

Definition of curve fitting using a second order polynomial fit.

Calibration should be carried out in 10% intervals throughout the range.  If lower load limits are required less than 10% intervals may be used.  A total of 30 force applications are required with at least ten different forces used. 

Good calibration practices, like temperature control and application of weights are described. Temperature should not change by more than ±1.0º C during the calibration.

Before each calibration, the load cell should be preloaded to the maximum force at least two times to establish the hysteresis pattern. 

A total of three calibrations are required with a one-third or 120º rotation between each of the calibrations. A total of 30 force applications must be made with at least ten different forces. 

The uncertainty is defined as 2.4 times the standard deviation. The standard deviation uses the differences between each reading and the corresponding curve fit data point. 

For Class AA load cells (instruments used as secondary standards), the uncertainty must not exceed 0.05% and the lower load limit is 2,000 times the uncertainty. 

For Class A load cells (instruments used to verify test equipment), the uncertainty must not exceed 0.25% and the lower load limit is 400 times the uncertainty.

For devices with temperature compensation built in the error due to temperature on Class AA load cells should not exceed 0.01% and 0.05% for Class A load cells. 

Class AA load cells (secondary standards) need to be calibrated annually. Class A load cells shall be recalibrated one year after the first calibration and then every two years, if the first recalibration did not change by 0.1% from the first calibration.

The report or calibration certificate should include the following: the reference standard used for the calibration including a statement of errors and uncertainty, the coefficients from the curve fit equations, the uncertainty with the calibration results and the limits of the Class A load range. The report is not required to state the accuracy, linearity or hysteresis of the load cell.