Particle sensor for detecting particles in a fluid, the sensor comprising: an emitter for emitting an electromagnetic wave, a detection space for containing the fluid; a detector comprising a reference fluid chamber and a reference pressure or temperature sensor, wherein the reference fluid chamber contains a reference fluid, wherein the reference pressure or temperature sensor is arranged to sense a pressure or temperature wave of the reference fluid in the reference fluid chamber, and a controller for detecting a particle and a further particle in the fluid based on the pressure or temperature wave sensed in the reference fluid chamber, wherein the emitter (1, 1') is configured to create an electromagnetic wave with a first emission spectrum modulated with a first modulation scheme and to create a further electromagnetic wave with a second emission spectrum modulated with a second modulation scheme, wherein the first modulation scheme and the second modulation scheme are distinguishable, wherein the second emission spectrum being different from the first emission spectrum, wherein the reference fluid comprises the particle to be detected or another particle which has similar absorption characteristics for the electromagnetic wave as the particle to be detected, wherein the reference fluid comprises a further particle to be detected in the fluid or another particle which has similar absorption characteristics for the further electromagnetic wave as the further particle to be detected, wherein the controller is configured to detect the particle to be detected based on the pressure or temperature wave according to the first modulation scheme and to detect the further particle to be detected based on the pressure or temperature wave according to the second modulation scheme, wherein the emitter and the detector are arranged such that the electromagnetic waves (2, 2') with the first emission spectrum and with the second emission spectrum traverse the detection space, and such that at least a part of the electromagnetic wave with the first emission spectrum which traversed the detection space enters the reference fluid chamber, and such that at least a part of the electromagnetic wave with the second emission spectrum which traversed the detection space enters the reference fluid chamber. an emitter for emitting an electromagnetic wave, a detection space for containing the fluid; a detector comprising a reference fluid chamber and a reference pressure or temperature sensor, wherein the reference fluid chamber contains a reference fluid, wherein the reference pressure or temperature sensor is arranged to sense a pressure or temperature wave of the reference fluid in the reference fluid chamber, and a controller for detecting a particle and a further particle in the fluid based on the pressure or temperature wave sensed in the reference fluid chamber, wherein the emitter (1, 1') is configured to create an electromagnetic wave with a first emission spectrum modulated with a first modulation scheme and to create a further electromagnetic wave with a second emission spectrum modulated with a second modulation scheme, wherein the first modulation scheme and the second modulation scheme are distinguishable, wherein the second emission spectrum being different from the first emission spectrum, wherein the reference fluid comprises the particle to be detected or another particle which has similar absorption characteristics for the electromagnetic wave as the particle to be detected, wherein the reference fluid comprises a further particle to be detected in the fluid or another particle which has similar absorption characteristics for the further electromagnetic wave as the further particle to be detected, wherein the controller is configured to detect the particle to be detected based on the pressure or temperature wave according to the first modulation scheme and to detect the further particle to be detected based on the pressure or temperature wave according to the second modulation scheme, wherein the emitter and the detector are arranged such that the electromagnetic waves (2, 2') with the first emission spectrum and with the second emission spectrum traverse the detection space, and such that at least a part of the electromagnetic wave with the first emission spectrum which traversed the detection space enters the reference fluid chamber, and such that at least a part of the electromagnetic wave with the second emission spectrum which traversed the detection space enters the reference fluid chamber.