AASHTO R 33-20

AASHTO R 33-20 covers the calibration of the reference load cell that is used for calibration of a Falling Weight Deflectometer (FWD) in R 32. It is used to establish calibration coefficients for the reference load cell.

This procedure has been automated in a software package named RefLCCal. It is required that the computer program be used to carry out the procedure.

Reference load cell calibration is performed at least once per year, or immediately after the reference load cell fails to pass certain quality assurance checks in the R 32 software (WinFWDCal).

The reference load cell, the cables, the associated signal conditioner, and the data acquisition system are considered a system of instruments that shall be calibrated together and used together.

This procedure results in load cell calibration coefficients that are entered into the R 32 software. These factors are used in WinFWDCal to convert analog voltage readings from the reference load cell to engineering units.