High/low voltage switching excitation system of electromagnetic flowmeter with bypass and energy feedback circuit

Abstract

The invention relates to a high / low voltage switching excitation system of an electromagnetic flowmeter with a bypass and an energy feedback circuit. The excitation system comprises an adjustable low voltage source circuit, a high / low voltage switching circuit, a constant-current circuit, a bypass circuit, an H-bridge excitation circuit, an excitation control circuit, a logic switching circuit, apower supply detection circuit, the energy feedback circuit and an energy leakage circuit. A practical excitation current detected on a current detecting resistor is compared with an excitation current threshold set in the logic switching circuit, thereby obtaining a control logic which is used for controlling the high / low voltage switching circuit and the bypass circuit, so as to select an excitation work voltage; introduction of the bypass circuit accelerates the response velocity of the excitation current in a coil obviously; the energy feedback circuit stores the energy fed back from an excitation coil; the power supply detection circuit, the energy leakage circuit and a switching protection circuit perform electrification, outage and error protection on the excitation system. The excitation system related to the invention improves the utilization rate of power supply, accelerates the response speed of excitation current, broadens the range of excitation frequency and provides circuit fault protection.

Description

technical field [0001] The invention relates to the field of flow detection, and is an electromagnetic flowmeter using high and low voltage for excitation, especially a high and low voltage switching as the core, a combination of logic switching circuit, constant current circuit and bypass circuit, supplemented by energy feedback The high and low voltage excitation system of circuit, power monitoring circuit, energy discharge circuit and excitation control circuit. Background technique [0002] The electromagnetic flowmeter mainly provides excitation current to the excitation coil in the sensor through the excitation circuit to generate a magnetic field of a certain strength. The direction of the magnetic field is perpendicular to the direction of fluid flow in the sensor. , an induced electromotive force of a certain intensity will be induced on both sides of the conductive fluid, and the amplitude of the electromotive force is proportional to the flow velocity when the mag...

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Problems solved by technology

However, this electromagnetic flowmeter excitation control system still has the following deficiencies: (1) The parameter distribution characteristics of the constant current control circuit are not good due to the poor parameter distribution characteristics of the Darlington tube and the triode connected to its base, which makes it difficult to realize it in practice. Carry out constant current control; (2) Use a common comparison circuit to control the power switching circuit. In the actual implementation, due to the common noise interference in the environment, the noise signal is superimposed on the output signal of the current detection resistor, so that the power switching The circuit frequently switches between high voltage and low voltage, and the output excitation current is unstable

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