| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent malfunction when a DC is applied to detect, for example, the passage of a pinball game ball by constituting an LC oscillation circuit by a coil and a capacitor that are wound around a pot core using a metal dust core. SOLUTION: An LC oscillation circuit is composed of an air-core coil 4 that is wound around a pot core 3 whose one part is opened and a capacitor, and a sendust dust core is used for the pot core 3. As for the B-H characteristics of a sendust core, a magnetic flux density gradually increases for a magnetization force, and cannot be saturated even with a magnetization force of, for example, 100 oersted. The change in inductance when a DC magnetic field is applied is approximately 1/2 as compared with that of ferrite core due to the influence of absence of a core in the case of the sendust dust core, but does not decrease rapidly to the DC magnetic field, and Q characteristic is slightly smaller than that of the ferrite core, thus preventing malfunction due to, for example, the application of DC magnetic field since the effect for preventing the transmission stop due to the DC magnetic field is great.</p> |
