Table 5.

Overview of the measuring systems used to monitor the nutrient consumption: measurands, sensors and measurement procedures.

	Measurand	Measuring Transducer	Measurement Procedure	Ref.
Nutrient flow	Air flow into the bottle	Thermistor	Sensor fixed to the lumen of a rigid tube inserted into the reservoir bung	[10]
		Pneumotachometer	Inserted at the top of the nutrient reservoir	[54]
	Milk flow	Ultrasonic flow transducer	Placed between the nipple and the bottle	[55]
Nutrient volume	Nutrient weight	Balance	Residual milk weighted continuously or at intervals	[29,48]
	Nutrient volume	Graduated reservoir	Residual milk volume measured from the graduated reservoir	[27,32,39]
	Hydrostatic Pressure	PT	PT connected to a catheter placed at the base of the residual liquid column;	[50,56]
	Intra-bottle vacuum	PT	PT connected to the top of the bottle, where the vacuum creates	[23]