Abstract: An apparatus for detecting the presence or absence of foreign matter in a product is provided which includes a reaction signal generating circuit 2 for outputting a reaction signal associated with the product by detecting a change in pattern of distribution of magnetic fluxes when the product P is passed through an alternating magnetic field; a determining circuit 10 for comparing a value of the reaction signal at a predetermined phase point p1 with a threshold value SH to thereby determine the presence or absence of the foreign matter in the product; and a sensitivity adjusting circuit 12A for adjusting a sensitivity of the reaction signal generating circuit 2 so that the value of a first test reaction signal A at the predetermined phase point p1, which is obtained when a product P added with foreign matter of a minimum size to be detected is passed through the alternating magnetic field, attains a desired level relative to the threshold value SH.

Abstract: In order to provide a combination weighing apparatus having an automatic filter adjusting capability which is effective to secure a weighing accuracy and also to adjust a filter characteristic of a digital filter having a short response time, the filter characteristic is automatically adjusted, based on a result of comparison of respective vibration components U of filtered weight signals FW1 to FWn with a permissible level US of the vibration components, so that the respective vibration components U of the filtered weight signals FW1 to FWn can attain a value approximating to the permissible level US, but not exceeding the permissible level US. In this way, by damping the vibration components U down to a value within the permissible level US, the weighing accuracy can be secured and, on the other hand, by damping the vibration components U down to a value approximating to the permissible level US, the filter characteristic can be obtained quickly in a short time.