JPS5764128A - Loose parts monitor - Google Patents

Abstract

PURPOSE:To prevent false detection owing to noise and to detect foreign matter accurately despite the small ground level by detecting the foreign matter of apparatus from the acoustic sensor output level obtained in the output of an amplification factor variable amplifier. CONSTITUTION:The acoustic signal (a) from an acoustic sensor is applied to a divider 10 as its numerator input, and in an average value circuit 20, the average voltage of the signal (a) is detected and is applied as a signal (b) to a limiter 30. The limiter 30 applies an output average value signal (c) to the divider 10 as its denominator input. Hence, the acoustic signal (d) preventing the amplification factor from increasing unlimitedly is obtained.