How can I check the calibration of the Pile Driving Analyzer® (PDA)?

The calibration of the internal circuits of the PDA can be checked by connecting the sensors and setting the accelerometer and force calibration to a preset number, and then generating a Calibration Test (CT). The calibration accuracy of the PDA signal conditioning can be evaluated by looking at the maximum velocity (VMX), which checks both the accelerometer input circuit and the integration process, and by looking at the maximum strain (MEX). The (dimensionless) maximum strain MEX is independent of pile properties. The calibration settings and the resulting values of MEX and VMX depend on the PDA model:

•PAK and PAL: accelerometer calibrations should be set to 834; force calibrations should be set to 147.5; MEX should read 737.5; VMX should read 4.02 m/s (13.2 ft/s).

•PAX: PE accelerometer calibrations should be set to 100; force calibrations should be set to 147.5; MEX should read 737.5; VMX should read 4.09 m/s (13.4 ft/s).

•8G: PE accelerometer calibrations should be set to 385; PR accelerometer calibrations should be set to 1000; force calibrations should be set to 147.5; MEX should read 737.5; VMX should read 4.09 m/s (13.4 ft/s) for PE or 4.21 m/s (13.8 ft/s) for PR.

All results should be within +/- 2% of the values shown above. If they are not, the unit must be sent to Pile Dynamics or one of its authorized agents for recalibration.

Important: the above procedure will only check the signal conditioning of piezoelectric (PE) accelerometers. An external calibration box (available from Pile Dynamics, Inc.) is needed to check the signal conditioning of piezoresistive (PR) accelerometers,

Note that if you save the Calibration Test signal before you start a test, that CT signal can be later replayed using the calibration factors specified above. It will then be possible to confirm that the internal calibration of the PDA was correct when the test was done. PDI recommends that a CT signal be saved with the actual pile test data at least once per day per job site.

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