Linear flow meter based on thermodynamic laws - measures temp upstream and downstream of heat source in fluid flow

摘要

Gas (1) whose flow is to be measured passes along a tube (2) containing a resistive heat source (3) powered from a regulated supply (40) ensuring a constant number of calories per unit time. Two thermometric probes with low thermal inertia are placed upstream (4) and downstream (7) of the heat source. Two probe outputs (5, 8) of the same polarity are connected together (50) while the second outputs (6, 9) provide an output voltage proportional to temperature differences of the probes. The flow is determined from this measurement using the calorific capacity of the gas and heat flow. A thermal screen (10) between the heat source and downstream probe aids mminiaturisation.