Patent ID: 7895904

Claim:
A multi-vortex flowmeter using a mass flow rate for determining a switching point, comprising: a vortex flowmeter for measurement of a volume flow rate; and a thermal flowmeter for measurement of the mass flow rate to selectively use the vortex flowmeter and the thermal flowmeter based on a flow rate of a fluid to be measured flowing through a flow channel, wherein the switching point between the vortex flowmeter and the thermal flowmeter is based on the mass flow rate, and a mass flow rate Qm at the switching point in a range larger than a minimum flow rate of the vortex flowmeter and smaller than a maximum flow rate of the thermal flowmeter is determined by: Qm=K3*√P (where P is a pressure of the flow channel (variable), K3 is a constant determined by an area of the flow channel, a vortex differential pressure, a constant related to the vortex differential pressure, a density at 0° C. and 1 atm, and a pressure at 1 atm).