主要是看中其高精确度。 Generally speaking, the choice of a turbine flow meter is mainly due to its high accuracy. At present, the accuracy of turbine flowmeters is roughly liquid: imported brands are ± 0.15% R, ± 0.2% R, ± 0.5% R, and ± 1% R, and domestic styling products are ± 0.5% R and ± 1% R; gas: Imported brands are ± 0.5% R and ± 1% R, and domestic brands are ± 1% R and ± 1.5% R. The above accuracy refers to a flow range of 6: 1 or 10: 1. In addition to its own product quality, accuracy is also closely related to the conditions of use. If the range is narrowed, the accuracy can be improved; especially the standard flow meter as a standard meter flow standard device, the accuracy can be greatly improved if it is used at a fixed point. The higher the accuracy of the turbine flowmeter, the more sensitive it is to changes in field conditions. To maintain its high accuracy, special treatment of the meter coefficients is required. One processing method is the so-called meter coefficient floating processing method. That is, the following conditions are processed in real time:
1. Viscosity is affected by temperature; 2. Density is affected by pressure and temperature; 3. Sensor signal redundancy (one sensor outputs two signals to monitor the ratio; d) Long-term stability of the coefficient (determined by control chart) Wait. For trade storage and transportation transfer measurement, it is often equipped with an online calibration device to facilitate regular calibration. The accuracy of the turbine flowmeter listed in the manufacturer's instruction manual is the basic error. The additional error should be estimated on the site, and the on-site error should be a combination of the two.
Structural characteristics of turbine flowmeter
传感器由表体、导向体（导流器）、叶轮、轴、轴承及信号检测器组成 The turbine flowmeter sensor is composed of a meter body, a guide body (a deflector), an impeller, a shaft, a bearing and a signal detector.
1. Meter body: The meter body is the main component of the turbine flowmeter sensor. It plays the role of bearing the pressure of the fluid to be tested, fixedly installing the detection component, and connecting the pipeline. The body is made of non-magnetic stainless steel or hard aluminum alloy. For large-diameter sensors, a combination of carbon steel and stainless steel has been used, and a signal detector is installed on the outer wall of the surface. 2. Guide body: A guide body is installed at the inlet and outlet of the turbine flowmeter sensor, which guides and rectifies the fluid and supports the impeller. Usually, it is made of non-magnetic stainless steel or hard aluminum. The rear deflector of the reverse thrust turbine flow sensor also needs to be able to generate sufficient reverse thrust, and it has many structural forms. The front deflector has a patented product that resists severe interference with fluid flow. 3. Turbine: Also known as impeller, it is the detection element of the turbine flowmeter sensor. It is made of highly magnetically permeable material. Impellers have straight blades, spiral blades, and T-shaped blades, and can also use a porous shroud ring embedded with many magnets to increase the frequency of a certain number of blade turbines. The number of leaves depends on the size of the aperture. The geometry and size of the impeller have a great impact on the performance of the sensor. The dynamic balance of the impeller is important to design according to the properties of the fluid, flow range, and use requirements, which directly affects the performance and service life of the instrument. 4. Shaft and bearing: It supports the impeller to rotate, and it must have sufficient rigidity, strength and hardness, wear resistance, corrosion resistance, etc. It determines the reliability and lifetime of the sensor. Sensor failure is usually caused by shafts and bearings, so its structure and material selection and maintenance are very important. 5. Signal detector: Variable magnetoresistive type commonly used in China, consisting of permanent magnetic steel, magnetically conductive rod (iron core), coil, etc. Permanent magnetic steel is attractive to the blades and generates reluctance torque. At small flow rate sensors, the reluctance torque becomes the main item among the resistance torques. For this reason, permanent magnetic steel is divided into two sizes, small diameter Small size to reduce reluctance torque. 输出信号有效值在10mV以上的可直接配用流量计算机，配上放大器则输出伏级频率信号。 The flowmeter output signal with an effective value of more than 10mV can be directly used with a flow computer, and an amplifier can output a volt-level frequency signal.