| 摘要 |
PURPOSE:To transmit the thermoelectromotive force of a thermocouple to an instrument body without being affected by the variation of the temperature of a reference contact and the noise, by providing an electrophoto converting circuit having a light emitting element, a detecting circuit which detects the variation of temperature, and a temperature compensating circuit. CONSTITUTION:In a connection box 1, the thermoelectromotive force of each thermocouple 2 is converted to a corresponding optical signal by an electrophoto converting circuit 6 and is transmitted to the instrument body through an optical fiber 14. In this case, a part of the optical signal emitted from a light emitting element 12 of the electrophoto converting circuit 6 is received by a detecting circuit 16 to detect the temperature variation of the electrophoto conversion efficiency of the light emitting element 12. The detection signal outputted from the detecting circuit 16 in accordance with the temperature variation of the light emitting element 12 is used as a temperature compensating signal. That is, the thermoelectrpmotive force changed by the temperature of the reference contact of the thermocouple 2 is compensated with respect to temperature on a basis of the detection signal given form the detecting circuit 16. Thus, data of the thermoelectromotive force obtained by the thermocouple 2 is transmitted to the instrument body without being affected by the variance of the temperature of the reference contact and the noise. |
