Excitation circuit for electromagnetic flow meter

Abstract

The invention discloses an excitation circuit for an electromagnetic flow meter. The excitation circuit comprises a constant current circuit, a sensing coil, an H-bridge circuit and an H-bridge circuit control loop; the constant current circuit provides a constant current for the sensing coil through the H-bridge circuit, all control signal output ends of the H-bridge circuit control loop are connected to all control ends of the H-bridge circuit respectively, and the two ends of the sensing coil are connected to the two output ends of the H-bridge circuit respectively; the constant current circuit is a switching-mode constant current circuit and comprises a switch driving chip, a starting circuit, a switch frequency selection circuit, an error amplification and compensation circuit and an output filtering circuit; the output end of the switch driving chip is connected to a positive input of the H-bridge circuit through the output filtering circuit, a negative input of the H-bridge circuit is grounded through a current sampling resistor, and the switch driving chip collects a current signal through the current sampling resistor, so that voltage input to the H-bridge circuit is variable direct voltage, and the current passing through the sensing coil is constant.

Description

technical field [0001] The invention relates to electromagnetic flowmeter technology, in particular to a switch-mode constant current excitation circuit for sensor coils of the electromagnetic flowmeter. Background technique [0002] An electromagnetic flowmeter is an instrument used to measure fluid flow. The excitation circuit is an indispensable and important part of the electromagnetic flowmeter. Its function is to generate an excitation current with a controlled size and timing to excite the sensor coil to generate a magnetic field. The fluid cuts the magnetic field lines in the pipeline, and induces electromotive force at both ends of the signal electrode. The magnitude of the induced electromotive force is proportional to the magnetic induction intensity and the flow velocity of the fluid. [0003] Existing electromagnetic flowmeters keep the magnetic field strength constant by controlling the excitation current. The existing typical excitation circuits used in elect...

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Problems solved by technology

The constant current circuit of the above patent uses operational amplifiers and transistors to form an analog linear constant current circuit. It also loses a lot of storage power and requires the use of a radiator. The heat generated by the radiator will increase the temperature of the circuit board and affect the performance of the circuit board. Due to the use of radiators, the size of the circuit board will increase, and the overall cost of the circuit design will be high. The most important thing is that the overall power consumption of the electromagnetic flowmeter will increase a lot due to the large loss of useless power.

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