Flowmeter accuracy decline processing method

There are many kinds of current flowmeters , but there are several commonly used volumetric flowmeters, electromagnetic flowmeters, turbine flowmeters, and vortex flowmeters. The accuracy of the flowmeter is generally determined at the factory reference conditions. Factors affecting the reference conditions include environmental conditions, electromagnetic flowmeter power source conditions, and fluid conditions. However, the actual operating conditions of the flow meter are usually different from the reference conditions, and therefore, the accuracy may decrease during use. Moreover, the degree of accuracy of different meter changes is different. So, how can we handle the decrease in the accuracy of the flowmeter? The following Xiao Bian will give you a detailed description of the measures to reduce the accuracy of the flow meter.
1, throttling device
　　 The accuracy of such devices such as throttling devices generally does not require fluid calibration, and the factory inspection mostly uses the “dry label” method, and the basic accuracy can be calculated. The calculation is based on the “rated value” provided by the acquirer. The density of the medium can be automatically compensated and displayed intelligently. In this case, it is important to pay attention to whether the location where the instrument is installed meets the requirements of the instrument, such as the length of the straight pipe. If it does not meet the requirements, the calculation of its additional error should refer to the instrument's instructions. If the density of the medium is calculated manually, when the actual state of the fluid medium is different from the design state, the flow display value is multiplied by a correction factor for the general gas. T, Z, P are the rated working conditions at design time. The media temperature, compression factor, and media pressure; t, z, and p are the media temperature, compression factor, and media pressure under actual operating conditions, respectively. Obviously, the temperature and pressure of the fluid in the actual work are randomly changed. The artificial compensation of the ultrasonic flowmeter can only compensate for the average value, and the error is significant. The method is to use the intelligent instrument to automatically compensate. For ideal (or near-ideal) gases, this compensation accuracy is quite high, showing an accuracy of ± 1% for mass flow or standard volume flow.

The throttling device has certain requirements for the straight pipe section, and the additional error caused when the throttling device fails to meet the requirements is stipulated for the standard throttling device.
2, volumetric flowmeter
 
For the volumetric flowmeter under the actual working conditions, the additional error caused is usually due to the influence of the temperature and pressure of the fluid medium on the volume of the measuring chamber. Under the condition of the known cavity material, the volume change can be calculated and displayed. Meter readings are corrected. The viscosity of the actual fluid may also have an effect on meter readings, which should be considered in accordance with the meter's instructions. The length of the straight section does not generally affect its accuracy. This is an outstanding advantage of this type of instrument. This type of instrument shows the volumetric flow rate of the fluid in the operating state. The user usually needs the volume flow or the mass flow in the standard state, and the fluid density compensation is also required. Most of the new flowmeters now use smart display instruments and automatic density compensation.
3, electromagnetic flowmeter
 
　　 The principle of electromagnetic flowmeter is based on Faraday’s electromagnetic induction theorem. The inner diameter (flow area) of the sensor has influence on the measured value. When the pressure and temperature of the fluid medium is different from the reference condition, the change of the meter reading caused by the different flow area can be calculated. Come out, otherwise it will produce a certain amount of error. The meter has a lower requirement for the straight pipe section, and the user of the pressure transmitter should pay attention that there is no correction formula when the straight pipe section is insufficient. The meter measures the volumetric flow in the working state. If the volume flow or mass flow in the standard state is required, density compensation is still required.
4, turbine flowmeter

This meter is sensitive to the conditions on site and the user fully meets its requirements in order to maintain the factory accuracy. When the temperature and pressure of the fluid medium differ greatly from the reference conditions, the volume change of the sensor housing can be calculated based on the material of the sensor and the temperature pressure, and the meter reading can be corrected. When the viscosity of the fluid medium under working conditions is different from the viscosity of the calibration fluid, it should be corrected according to the viscosity correction curve provided by the instrument manufacturer. Turbine flowmeters have certain requirements on the length of straight sections upstream and downstream of them, and they should be managed, especially when the user requires high accuracy. The meter shows the volumetric flow under the working conditions of the media. To know the standard volume flow or mass flow, density compensation is also required. Turbine flowmeters have a high degree of measurement accuracy and are often used as standard gauges for calibrating work instruments.
5, vortex flowmeter
 
　　 Input-type hydrostatic level transmitter This type of instrument is sensitive to the conditions on site, and the user fully meets its requirements in order to maintain the factory accuracy. When the temperature, pressure, and reference conditions of the fluid medium are greatly different, the volume change of the sensor housing can be calculated based on the sensor material, temperature, and pressure, and the meter reading can be corrected. Vortex flowmeters have requirements for the lengths of straight sections upstream and downstream, and they should be managed, especially when the user requires high precision. The meter shows the volumetric flow under the working conditions of the media. To know the standard volume flow or mass flow, density compensation is also required.

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