ELECTROMAGNETIC FLOWMETER

PURPOSE:To remove a reduction in an output due to changes in the temperature of a magnet and enable a size and a weight to be reduced by generating a temperature correcting signal in accordance with the temperature of the magnet and correcting a flow rate signal by an output correcting signal obtained by applying the temperature correcting signal to a variable gain amplifier. CONSTITUTION:A permanent magnet 22 is built in the outside of a pipeline 20 wherein an electrically conductive fluid 21 flows and an induced power detecting electrode 25 is mounted to the pipeline 20. A signal detected 25 in accordance with a flow rate is amplified 28 and inputted to a correcting circuit 29 and a direct-coupled circuit 30. The circuit 29 has a reference resistor 31 in a normal temperature portion and a temperature measuring resistor 32 with a resistance value changing with the temperature of the fluid 21 is mounted to a high temperature portion, namely, the surface of the magnet 22. An output correcting signal obtained from both the ends of the resistor 32 is inputted to an arithmetic circuit 34 via a variable gain amplifier 33. By selecting the resistance value of the resistor 32, a temperature coefficient relative to the output of the amplifier 33 and the resistance values of the resistors 32 and 31, the temperature dependency of a flowmeter can be removed. Further, by adjusting the gain of the amplifier 33, the magnet 22 can be compensated for a secular change.