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.