PURPOSE:To improve heat resistance preventing outflow of a cooling water, by filling insulation coils with a heat resistant resin while a heat shielding case, a ring guard and a housing are arranged and bonded watertight. CONSTITUTION:Insulation coils 1 are housed into a heat shielding case 2 and a heat resistant resin 8 is filled between insulation coils 1 to solidify. Then, the side and the top of the heat shielding case 2 are covered with a ring guard 9 and joined together with an adhesive 10. A housing 4 is bonded watertight with an adhesive 12 outside the ring guard 9 through a heat resistant packing 11. In this manner, the insulation coils 1 are protected from a high heat to prevent outflow of a cooling water to a hot slab 7 and a transducer highly resisting to heat impact can be obtained thereby improving the heat resistance and durability.