How important is it to periodically have the Pile Driving Analyzer® (PDA-8G) sensors recalibrated?
Generally, Pile Dynamics, Inc.® (PDI) recognizes that both acceleration and strain transducers are stable and unlikely to change their calibration outside the specified tolerance of +/- 2%. In order to check the transducer's calibration, compare the velocity (times impedance) against the force at times of early impact. A good proportionality between velocity and force indicates the proper calibration of the strain and acceleration transducers. Conversely, the calibration process may identify a defective sensor. As a result, it is important for PDI or one of its authorized agents to periodically check that the sensors are performing to specification.
PDI and the American Society for Testing and Materials (ASTM) D4945 recommend that sensors be recalibrated every 2 years despite how often they are used. Additionally, PDI suggests that sensors exhibiting questionable data before 2 years should be recalibrated. PDI's policy is to recalibrate any sensor returned to its Maintenance Department for checkup or repair.