ABB 200900-004 DCS controller card

ABB 200900-004 DCS

The flow measurement tester is an industrial automatic appearance, also called flowmeter, used to measure the flow of liquid, gas or steam in pipelines or open ditches.

Flow refers to the amount of fluid flowing through the useful cross section of the pipeline in unit time. The amount of fluid expressed by volume is called volume flow, and the unit is m3/h, liter/h, etc. The quantity of fluid expressed by mass is called mass flow, and the unit is ton/hour, kilogram/hour, etc.

As early as 1738, the Swiss Daniel Bernoulli took Bernoulli equation as the foundation and used differential pressure method to measure water flow. Later, the Italian Venturi discussed the measurement of flow with Venturi tube, and announced the research results in 1791; In 1886, Herschel, an American, made a venturi tube into a useful device for measuring water flow.

From the early stage to the middle stage of the 20th century, the original measurement principles gradually became sophisticated, and people began to explore new measurement principles. Since 1910, the United States began to develop a groove flowmeter for measuring the water flow in open ditches. In 1922, Parshall transformed the original Venturi flume into Parshall flume.

From 1911 to 1912, Carmen, an American Hungarian, put forward a new theory of Carmen Vortex Street. In 1930s, the method of measuring the flow velocity of liquid and gas by acoustic wave was presented, but it was not greatly developed until the end of World War II. It was not until 1955 that the Maxon flowmeter with acoustic circulation method was used to measure the flow rate of aviation fuel. In 1945, Colin successfully measured the blood activity with alternating magnetic field.

After the 1960s, the measurement of appearance began to be refined and miniaturized. For example, in order to improve the accuracy of differential pressure appearance, force balance differential pressure transmitter and capacitive differential pressure transmitter are presented; In order to miniaturize the sensor of electromagnetic flowmeter and improve the signal-to-noise ratio, an electromagnetic flowmeter with non-uniform magnetic field and low-frequency excitation method is presented. In addition, the useful Karman vortex flowmeter with wide measuring scale and no moving detection parts also came out in the 1970s.

With the rapid development of integrated circuit skills, ultrasonic (wave) flowmeters with phase-locked loop skills have also been widely used. The wide use of microcomputers has further improved the ability of flow measurement. For example, the laser Doppler velocimeter can handle messy signals after using microcomputers.

Flow can be indirectly measured by various physical phenomena, so there are many kinds of appearance of flow measurement. According to the measurement methods, there are differential pressure flowmeter, variable area flowmeter, volumetric flowmeter, speed flowmeter and electromagnetic flowmeter.