Described herein is an in-line sensor for sensing properties of a pulsed milk flow on a continuous basis. A milking cluster comprising multiple pulsed milk flow inputs from lactating animal teats and a mixing point or claw for the multiple inputs is described that includes multiple in-line sensors for each pulsed milk flow input. Methods of use of the in-line sensor and milking cluster are also described. The in-line sensor described may be easily integrated into existing milking apparatus, is reliable, has a low cost, and is self-cleaning/self-emptying.