What does a turbine flowmeter consist of?

A turbine flowmeter is a type of velocity flowmeter, also known as an impeller flowmeter. It is based on the principle of conservation of angular momentum.

The structure of a turbine flowmeter is shown in the figure below. As fluid flows through a pipeline, it impacts the turbine blades, causing the turbine to rotate. The turbine's rotational speed varies with the flow rate. The flow rate is calculated from the turbine's rotational speed and is counted and displayed on a secondary instrument. This signal can reflect both instantaneous and cumulative flow (or total flow). It can also be converted into a standard signal for remote transmission. Furthermore, the pulse frequency signal output by the sensor can be used independently with a computer, replacing the flow meter with a flow display instrument to achieve density, temperature, and pressure compensation, indicating the fluid's volumetric or mass flow rate. It is one of the more mature and highly accurate flowmeters currently available.

Components
A turbine flowmeter typically consists of a rectifier, instrument section, sensor, and preamplifier.

The rectifier is a device installed in the pipeline upstream of the flowmeter to eliminate or reduce various non-axisymmetric and pulsating flows, such as vortices and eccentricity. The instrument section refers to the piping section that includes the rectifier, upstream and downstream straight pipe sections, and the flowmeter.
The sensor is a device that converts the rotor's rotation into an electrical signal. The turbine and its assembly (including the front and rear guide frames, bearings, housing, and preamplifier) ​​that senses fluid velocity in a turbine flowmeter are generally referred to as turbine flow sensors.
The preamplifier amplifies and shapes the sensor's electrical signal to generate an output signal. The signal processing and conversion portion of the output signal is called a secondary instrument or display instrument.