This invention relates to radiation pyrometer systems. 
The invention is more particularly concerned with pyrometer systems in which the effect of noise is reduced. 
Radiation pyrometers used in gas-turbine engines to obtain an indication of the temperature of the turbine blades, can suffer from noise caused by the passage of excessively hot particles, such as carbon particles, and flames in the field of view of the pyrometer.  Unless provision is made to compensate or reduce the effect of these anomalies as inaccurate measure of temperature can be given.  The high-temperature noise phenomena are generally of a transient nature and their effect can thereby be reduced readily by reducing the speed of response of the pyrometer system.  This technique can be useful in reducing noise but has the disadvantage of making the system unable to respond to other transient phenomena, such as the passage in front of the pyrometer of an overheated blade.  Another disadvantage of slow-response pyrometers is that transient signals which are unipolar in nature will, in effect, contribute a background signal causing errors in the estimation of mean temperature.  Since it can be useful in predicting engine failure to be able to detect the temperature of individual blades, a slow response pyrometer has distinct disadvantages.