Heat Loss Flowmeter for Water Based on Thick Film Thermistors in Power Save Regime

Abstract

Novel heat loss flowmeter for water consists of the small plastic housing and two NTC thick film segmented thermistors with reduced dimensions placed along the main axis. The segmented thermistors were printed using the modified nickel-manganese paste and sintered in air at 850 degrees C / 10 min in the conveyor furnace. The first thermistor Th-1 is cold and measures input water temperature and the second thermistor Th-2 is self-heated at constant voltage and measures water flow rate. A short switch mode operating cycle for the self-heating thermistor was introduced: 30s of self-heating from the initial state and after that 90s of natural cooling to the initial state. The self heating DC current in 30th second I-30 is recognized as the flowmeter response on stable water flow Q, while input water temperature T-w was used as a parameter. The flowmeter temperature range was divided in a few sub-ranges and adaptive DC voltage power supply (RCV) was introduced for each sub-range. The flowmeter measuring range and inaccuracy were compared with respective ones of other flowmeters.