Mono-dual frequency electromagnetic flowmeter excitation control system based on linear power supply

Abstract

The invention relates to a mono-dual frequency electromagnetic flowmeter excitation control system based on linear power supply, comprising a constant current source circuit, a current bypass circuit,an exciting coil driving circuit, an excitation time sequence generating circuit and a galvo circuit. A high voltage power supply is adopted for supplying power, the constant current source is constructed by linear power supply to supplying electricity for the exciting coil driving circuit, the current bypass circuit is jointed in parallel with the input / output end of the linear power supply to solve the problem of energy dissipation, the exciting coil driving circuit is composed of an H bridge and a control circuit thereof, the galvo circuit is bridge-jointed between the lower end of the H bridge and a reference ground, and a digital signal processor (DSP) is used for controlling multiple switches and an electrical level matching device to generate time sequence and control the action ofthe exciting coil driving circuit. The excitation control system can obviously improve excitation frequency range and excitation frequency preciseness, is suitable for single frequency high frequencysquare wave excitation or dual frequency square wave excitation, and can simultaneously provide more exact current detection to correct the flow signal processing result.

Description

technical field [0001] The invention relates to the field of flow detection, and is an electromagnetic flowmeter excitation control system based on a linear power supply and using a DSP control hardware circuit that can realize single-frequency high-frequency square wave and double-frequency square wave excitation. Background technique [0002] The electromagnetic flowmeter applies a magnetic field to the measured fluid through the excitation coil, and the measured fluid moves in the magnetic field to induce an induced electromotive force, and the fluid flow velocity can be obtained by detecting and processing the electromotive force signal, thereby realizing flow measurement. At present, the excitation method is mainly low-frequency square wave excitation, that is, the excitation coil is powered by a constant current source, and the direction of the current in the excitation coil is constantly switched, so that the excitation current changes periodically between positive and...

AI Technical Summary

Problems solved by technology

[0006] The technical solution adopted in the present invention is: use a high-voltage source for power supply, use a linear power supply to construct a constant current source, and supply power to the excitation control H-bridge to improve the dynamic response speed of the excitation constant current control, thereby providing a stable zero-point high-frequency Single-frequency square-wave excitation or dual-frequency square-wave excitation provides conditions; a current bypass circuit is used to solve the power dissipation problem on the linear power supply; the constant current control circuit of the linear power supply is located at the high end of the H bridge (power supply end), and the low end of the H bridge Only the low-resistance current-sensing resistor is connected to the reference ground to ensure the stability of the low-end of the H-bridge; the high-end bridge arm of the H-bridge uses a flow control device PNP tube as the switch tube, and controls its conduction through the current to avoid the high-end voltage. It is difficult to stabilize the problem of stable control. The low-end uses a voltage-controlled device MOS tube as a switch tube, and its conduction is controlled by voltage; since the current-sensing resistor is located between the low-end of the H-bridge and the ground, the gate current of the MOS tube is very high. In addition, the linkage control of the H-bridge diagonal switching devices is implemented during the excitation process, so as to ensure the accuracy of the excitation current detected by the current-sensing resistor in each stage of the excitation; the switch control circuit of the H-bridge is combined by a Darlington array tube The triode and resistors are implemented; the Darlington array tube receives the excitation sequence signal from the excitation sequence generation circuit; the excitation sequence generation circuit is composed of a digital signal processor (DSP) with multiple switches and level matching devices, and the excitation sequence control signal is composed of digital The peripherals on the signal processor (DSP) chip control the generation, and do not require software participation in the excitation process, thereby improving the accuracy of the excitation frequency

Images