Abstract: A heating element device is provided with a heat dissipation case (2) made of metal having a first case plate (2a) and a second case plate (2b) which have peripheral edge portions (6, 9) air-tightly connected to each other. A plurality of ceramic semiconductor heating elements (14) are sandwiched between the both case plates (2a, 2b) through electrode plates (16) in between. An electricity supply path (4b) to each of the electrode plates (16) is disposed air-tightly to the inside of the heat dissipation case (2). Moreover, a hollow portion in the heat dissipation case (2) is maintained in a vacuum state so that an inner face (8) of the first case plate (2a) and an inner face (12) of the second case plate (2b) are always subjected to an attraction force in a direction in which they get closer to each other.

Abstract: The humidity within a controlled chamber is detected with a humidity detector, the proportional value, integrated value and differentiated value of the difference between the detected signal and a preset objective value signal are added to be an operation amount signal and an oscillator of an ultrasonic humidifier is oscillated with an amplitude adjusted in response to this operation amount signal to keep the humidity within the controlled chamber constant.

Abstract: The humidity within a controlled chamber is detected with a humidity detector and the proportional value, integrated value and differentiated value of the difference between the detected signal and a preset objective value are added to form an operation amount signal. A predetermined period is divided into a spray time during which an oscillator of an ultrasonic humidifier is operated at an amplitude obtaining a predetermined sprayed amount per unit time and a stopping time during which the oscillator cooperated with such small amplitude as to generate no spray. The predetermined period is repeated and the spraying time in each fixed period is adjusted in response to the above mentioned operation amount signal to keep the humidity within the controlled chamber constant.