Rebound hammer

Abstract

A measuring apparatus which detects defects in underwater concrete structs by measuring the compressive strength of the structure. The measuring apparatus comprises a rebound hammer which has extending from the nose thereof a plunger. The plunger is pressed against the structure whose compressive strength is being measured forcing the plunger into the rebound hammer's housing which releases a spring driven mass. A resistive film strip which is in electrical contact with the mass detects the maximum rebound of the mass and provides an electrical signal indicative of this maximum rebound. A data acquisition and processing circuit comprising a microprocessor and signal conditioning electronics receives, processes and stores the electrical signals provided by the resistive strip. This circuit includes a peak detection circuit which captures the peak output signal from the resistive strip. The peak detection circuit then interrupts the microprocessor and sends an analog signal proportional to the maximum rebound of the mass to an analog to digital converter which converts the analog signal to a digital data for processing by the microprocessor. The microprocessor then calculates the compressive strength of the underwater concrete structure under test.