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Description / Abstract:
This standard practice covers the annual calibration of the load
cell and the deflection sensors and monthly relative calibration of
the deflection sensors of a falling weight deflectometer (FWD) or a
heavy weight deflectometer (HWD). It is used to establish
calibration factors for correcting FWD and HWD measurements.
For this practice, the term "FWD" also refers to an HWD unless
otherwise noted.
This procedure is not applicable to the calibration of
lightweight deflectometers or of cyclic loading and other types of
pavement deflection testing equipment.
Annual calibration is performed at least once per year or as
soon as possible after a deflection sensor or a load cell has been
replaced on the FWD. It shall be performed by a certified
technician.
Monthly relative calibration is performed on the deflection
sensors at least once per month and immediately after a deflection
sensor is replaced. A certified technician is not required.
The procedure results in calibration factors that are entered
into the FWD software as multipliers. When the FWD measurements are
multiplied by the calibration factors, the result is a set of
measurements that have been corrected to agree with the calibration
instrumentation.
Calibration procedures may vary slightly among FWD types. This
procedure can be used for all types of FWDs with minor
modifications within the limits of the reference calibration
equipment.
This procedure has been automated in the software package
WinFWDCal. It is required that the computer program be used to
carry out the procedure.
To use this procedure, the FWD computer shall be capable of
electronic data transfer.
Data files for all types of FWDs can be read by the
WinFWDCal software. The PDDX file format (Section 3.1.11) is
required for data input. FWD data files that are in native format
can be converted to PDDX format using PDDXconvert, which
is an integral component in WinFWDCal.
The values stated in SI units are to be regarded as standard.
U.S. Customary units given in parentheses are for information
purposes only.
This standard practice may involve hazardous materials,
operations, and equipment. It does not purport to address all of
the safety concerns associated with its use. It is the
responsibility of the user of this standard practice to consult and
establish appropriate safety and health practices and determine the
applicability of regulatory limitations prior to use.