Apparatus for detecting metal

Abstract

Abstract PURPOSE:To make it possible to detect the presence of a minute amount of a metal with high accuracy without being affected by noise, by outputting a detection signal only when a second inverse phase non-equilibrium signal is obtained after a predetermined time is elapsed from a time when a first non-equilibrium signal is obtained. CONSTITUTION:When an object W to be inspected passes a first and a second receiving coils 3a, 3b and the presence of a metal mixed therein is ascertained, the output signal of a DC amplifier 7 rises, while starting the timer operation of a timer 15 by the rising in the output signal of a comparator 11 changed as shown by the drawing, and falls after a time To when the object W to be inspected reaches the center of the coil 3b from the center of the coil 3a is elapsed and a monostable multi-vibrator 17 outputs a pulse. Because the output of the comparator 12 is concincided with the timer 15 at the time of rising, a metal detection signal is issued from an AND circuit 19. When noise does not exceed a reference level Vo, the output is generated from the comparator 11 but the output is not generated from the comparator 12 and, therefore, the metal detection signal is not generated.

Inventors

• 👤 Fujio Kamata
• 👤 釜田　冨士夫
• 👤 Yasumoto Suzuki
• 👤 鈴木　康元

Bibliographic Details