A heat radiation sensing device is provided, which comprises two receiver surfaces which are exposed to the radiation, one of which comprises a high absorption ability with respect to the heat radiation by means of a black coloring, while the other has a low absorption ability by means of a covering which reflects the heat radiation. These two receiver surfaces consist of NTC resistor material and are combined to form a bridge circuit with two cermet resistors which are independent of temperature. The four resistors are applied to a ceramic substrate and are connected with conductor path which, in turn, end in the four required connections. The ceramic substrate is fixed in a frame which carries a covering which is pervious to heat radiation to a great degree and which, in turn, carries a layer having a window over one of the two NTC resistors the layer is made of a material which reflects the heat radiation to a great degree.

A temperature sensor, e.g. a thermistor (24, 37, 41, 46, 50', 57) is provided in a hollow space in cup-shaped shell (22, 36, 39, 42, 50, 54) of a size, e.g. 30 mm diameter and 15 mm depth, at a position of 1/3 height (i.e. 5 mm) of the depth from the bottom of the shell, the shell having wide opening (23, 33, 43, 47, 55) at its top part, and the temperature sensor is heated by feeding a controlled current to itself or to a heater provided at proximity thereto; the temperature sensor senses environmental condition in the similar manner to human sensation, taking account of air temperature, air flow and radiant heat from nearby matter such as wall or ceiling; thereby enabling comfortable air controlling.

Apparatus the temperature of a thermoplastic sheet including a hollow wave guide having a bend therein, for receiving and transmitting infrared energy emitted by the sheet between a sheet heater at a sheet forming station and differential pressure forming apparatus at a forming station. One end of the hollow channel is mounted adjacent the sheet. At the opposite end of the hollow channel, a plurality of infrared energy sensors is mounted for sensing the infrared energy. Infrared sensors include mechanism for converting the infrared energy to electrical energy to operate a control system which controls the level of electrical power to the heater and thus controls the temperature of the sheet.

In a thermal-environment sensor which detects thermal conditions in an indoor environment based on the surface temperature of a heating element supplied with a thermal quantity, the spectral emissivity of the outer surface of said heating element closely conforming to the spectral emissivity of the surface of the human skin or clothes thereon so as to bring the radiant heat transfer coefficient of the sensor remarkably near that of the human body.

A thermal environment sensor has a single temperature detector for detecting temperature and producing an output representative of the detected temperature, the temperature detector having, when heated by a predetermined constant power, a convective heat transfer coefficient giving it a wind velocity dependent temperature drop characteristic in close conformity with the wind velocity dependence of the effective temperature drop felt by a human body. A heater is provided for heating the temperature detector, and an electric power supply is connected to the heater for supplying the heater with a constant electric power corresponding to the predetermined constant power, and a temperature estimating circuit is connected to the temperature detector for correcting the output of the temperature detector by a predetermined constant temperature difference for thereby obtaining the effective temperature felt by a human body.