An apparatus to dispense fluids may include a reusable portion and a disposable portion. The disposable portion may include components that come into contact with the fluid, while the reusable portion may include only components that do not come into contact with the fluid. The apparatus includes an acoustic volume sensor that acoustically excites a fixed-volume chamber and a measurement chamber with a loudspeaker and measures the acoustic response with microphones acoustically coupled to the fixed volume chamber and the measurement chamber. The loudspeaker and sensing microphones are connected to the measurement chamber by separate ports. A detachable dispensing chamber is coupled to the acoustic volume sensor. The volume of the fluid dispensed is determined by a processor based on the acoustic response of the microphones to acoustic excitement by the loudspeaker.