METHOD FOR SELECTING OPERATION CENTER FREQUENCY OF HARDNESS MEASURING SYSTEM, APPARATUS FOR SELECTING OPERATION CENTER FREQUENCY OF HARDNESS MEASURING SYSTEM, AND HARDNESS MEASURING SYSTEM

摘要

To facilitate selection of the operation center frequency for a hardness measuring system that uses a phase shifter circuit to measure the hardness of an object. A hardness sensor is connected to an operation center frequency selecting apparatus. During a free terminal state of the sensor, a frequency-to-amplitude characteristic and the like are measured, and their peak frequency, phase and the like are measured as free-terminal characteristics (S10-S20). Next, the hardness sensor is caused to contact with a first test piece, and the frequency, phase and the like that have changed for the peaks are measured as first characteristics (S22-S28). The same measurements are performed with a second test piece, which is harder than the first test piece, to acquire second characteristics (S30-S36). These are used to perform, based on a predetermined selection reference, peak selections suitable for the hardness measurement, and its peak frequency is used to set the operation center frequency (S38-S40).