System for monitoring of temperature trends for particles moving along a path of movement from a first position to a second position, the system comprising: a sensor arrangement , a field-of-view of which is arranged in the path of movement of the particles to detect a signal related to the temperature of particles moving through said field-of-view, the sensor arrangement comprising at least one set of sensing elements detecting radiation emitted from the particles , each set comprising at least two sensing elements arranged to co-operate with mutually separated sensing zones along the path of movement of the particles ; and at least one processing device , which is arranged to: receive signals from the sensor arrangement ; form signals from the at least one set of sensing elements into at least one pulse train when a particle moves through the field-of-view of the sensor arrangement ; and based on this at least one pulse train, monitor changes over time in the temperature of particles moving through the field-of-view of the sensor arrangement by monitoring changes over time in the wavelength distribution of the radiation emitted from the particles , wherein the sensor arrangement comprises first and second sets of sensing elements , wherein the first set of sensing elements detects radiation of wavelengths within a first wavelength range, and the second set of sensing elements detects radiation of wavelengths within a second wavelength range, wherein the second wavelength range differs from the first wavelength range, characterized in that the at least one processing device is arranged to determine a relation between the signal strengths of the signals detected by the first and second sets of sensing elements , and based on this relation monitor changes over time in the wavelength distribution of the radiation emitted from the particles . a sensor arrangement , a field-of-view of which is arranged in the path of movement of the particles to detect a signal related to the temperature of particles moving through said field-of-view, the sensor arrangement comprising at least one set of sensing elements detecting radiation emitted from the particles , each set comprising at least two sensing elements arranged to co-operate with mutually separated sensing zones along the path of movement of the particles ; and at least one processing device , which is arranged to: receive signals from the sensor arrangement ; form signals from the at least one set of sensing elements into at least one pulse train when a particle moves through the field-of-view of the sensor arrangement ; and based on this at least one pulse train, monitor changes over time in the temperature of particles moving through the field-of-view of the sensor arrangement by monitoring changes over receive signals from the sensor arrangement ; form signals from the at least one set of sensing elements into at least one pulse train when a particle moves through the field-of-view of the sensor arrangement ; and based on this at least one pulse train, monitor changes over time in the temperature of particles moving through the field-of-view of the sensor arrangement by monitoring changes over time in the wavelength distribution of the radiation emitted from the particles , wherein the sensor arrangement comprises first and second sets of sensing elements , wherein the first set of sensing elements detects radiation of wavelengths within a first wavelength range, and the second set of sensing elements detects radiation of wavelengths within a second wavelength range, wherein the second wavelength range differs from the first wavelength range, characterized in that the at least one processing device is arranged to determine a relation between the signal strengths of the signals detected by the first and second sets of sensing elements , and based on this relation monitor changes over time in the wavelength distribution of the radiation emitted from the particles . <EOS>