Device and method for synthesizing start-up signal of Coriolis flowmeter with full digital waveform

Abstract

The invention relates to a device and a method for synthesizing Coriolis flowmeter vibration starting signals through all-digital waveforms. The device comprises a microcontroller, a direct digital frequency synthesizer (DDS), a multiplication digital-analog converter (MDAC) and an audio power amplifier. After the device is powered on, the DDS is controlled by the microcontroller to constantly synthesize and output 1-Hz square wave signals, at the same time, the microcontroller writes control words into the MDAC, the square wave signals passing the MDAC are subjected to amplitude modulation and amplification according to size of the control words and amplified by a fixed multiple through work, and final amplitude of the square wave signals is adjusted to 9 Vpp. The signals are input into a flow tube to realize quick vibration starting of the flow tube.

Description

technical field [0001] The invention aims at the driving system of the Coriolis mass flowmeter, and designs a 1Hz all-digital driving vibration starting device and method based on harmonic decomposition. Background technique [0002] Coriolis mass flowmeter (hereinafter referred to as Coriolis flowmeter) is a kind of direct mass flowmeter made by Coriolis principle. It is one of the most rapidly developing flowmeters. It can measure various conventional liquids, and can also be applied to the measurement of unconventional fluids such as slurry, liquefied gas and compressed natural gas, and is widely used in petrochemical, food and pharmaceutical industries. [0003] The Coriolis flowmeter is mainly composed of a flow tube (also known as a vibrating tube), a sensor, a signal processing system, and a drive system (also known as an excitation system). Among them, the performance of the drive system directly affects the overall measurement accuracy of the flowmeter. The tradit...

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Problems solved by technology

However, the design of this method is extremely complicated, and the control process is cumbersome. Due to the influence of industrial site environmental noise, etc., the zero point mentioned in the method is difficult to find. Even if a hysteresis band b is set near the zero point to avoid system malfunction caused by noise , but the value of b needs to be set according to the actual noise level. This method needs to determine the prior noise information of the scene in advance in different working scenarios, and cannot adapt to the environment well.

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