AASHTO R 33-20 PDF Download

AASHTO R 33-20 is a standard practice document that provides guidelines for the calibration of the reference load cell used in the calibration process of a Falling Weight Deflectometer (FWD). The purpose of this standard is to establish calibration coefficients for the reference load cell.

The calibration procedure described in this standard has been automated and is carried out using a software package called RefLCCal. It is mandatory to use this computer program for the calibration process.

According to the standard, the reference load cell calibration should be performed at least once per year. Additionally, it should be carried out immediately if the reference load cell fails to pass certain quality assurance checks in the R 32 software (WinFWDCal).

It is important to note that the reference load cell, cables, signal conditioner, and data acquisition system are considered as a system of instruments that must be calibrated together and used together.

The outcome of this calibration procedure is the determination of load cell calibration coefficients, which are then entered into the R 32 software. These coefficients are used in the WinFWDCal software to convert the analog voltage readings from the reference load cell to engineering units.