| 摘要 |
<p>A hardness measuring apparatus in which a frequency deviation detecting circuit is used has a contact element (5), an oscillator (3), a self-oscillating circuit (11) and a gain variation compensating circuit (13). The self-oscillating circuit (11) feeds back oscillation information of the oscillator (3) to generate a resonant state. The gain variation compensating circuit (13) is disposed in the self-oscillating circuit (11). The gain variation compensating circuit (13) has a central frequency different from that of the self-oscillating circuit (11), and increases gain in response to a change in frequency. <IMAGE></p> |
