| 摘要 |
PURPOSE:To implement an electromagnetic flowmeter without lining having a simple constitution, by utilizing a conductivity sigma of a fluid to be measured, a contact resistance (tau) between a pipe wall and the fluid, an electromotive force ev, which is generated between electrodes where an exciting magnetic field is imparted, performing specified computation, thereby obtaining a flow speed signal. CONSTITUTION:Switches SW1 and SW2 are conducted under a non-excited state, and an electric resistance R12 between signal electrodes 21 and 22 is measured. Then, the switch SW1 and a switch SW3 are conducted, and a resistance R0 between the signal electrode 21 and a pipe 1 is measured. The resistance values R12 and R0 are inputted to an operating circuit 8. Under the excited state, the switches SW1-SW3 are not conducted. An electromotive force ev based on an average flow speed (v) of a fluid to be measured, which is generated between the signal electrodes 21 and 22, is measured, and the result is applied to the operating circuit 8. At first, the operating circuit 8 performs specified computation by utilizing the resistance values R12 and R0 and obtains a conductivity sigma of the fluid to be measured and a contact resistance tau between the pipe wall and the fluid to be measured. Then, by utilizing the obtained sigma and tau and the voltage value ev, an average flow rate (v) of the fluid to be measured is obtained by the expression. |
