Abstract: A radiation thermometer comprises a housing (1) within which is mounted a radiation detector system including a radiation sensor (2) positioned to receive radiation through a window (5) in the housing. The radiation detector system generates an electrical signal related to the sensed radiation. An optical signal generator (11, 14) is responsive to the electrical signal from the radiation detector system (9) and an internal housing temperature detector to generate a modulated optical signal whose frequency is related to the electrical signal from the radiation sensor and whose mark-space ratio is related to the signal from the internal temperature detector. The housing (1) is connectable with an optical waveguide, such as an optical fibre (16), into which the optical signal is coupled in use. A power source (13) is mounted within the housing (1) and is connected to the detector system (9).

Abstract: Method and apparatus for monitoring the quality of a weld performed with an electrode mounted on an automatically controlled electrode support arm which moves between a rest position and a series of spaced operative positions in each of which a weld operation is performed. The apparatus includes a radiation detector for connection to a monitoring system and a radiation collector attached to the support arm adjacent the electrode and coupled to the radiation detector by optical fibers to receive in use a first level of radiation from electrode and a second level of radiation from the weld zone when the arm is in its operative position. A reference source of radiation is also provided that is located such that when the support arm is in its rest position, the collector receives a third level of radiation from the reference source, whereby the radiation detector generates three signals corresponding to the three levels of radiation impinging on the detector for supply to the monitoring system.

Abstract: A radiation thermometer comprises two radiation detectors for detecting radiation in wavelength bands centered on two different wavelengths .lambda..sub.1,.lambda..sub.2 (where .lambda..sub.1 >.lambda..sub.2) from a rotating body such as a gas turbine motor and for generating first and second signals S.sub.1,<S.sub.2 >respectively related to the radiance profile around said body and the average radiance around said body. A time averaging circuit generates a signal <S.sub.1 >representing an average value of said first signal. A dividing circuit generates a signal related to the ratio of <S.sub.1 >to <S.sub.2 >; and a monitor monitors at least one of said signals, predetermined arithmetic combinations of said signals, and quantities related thereto and provides corresponding output signals.