LC Type Elliptical gear flowmeter

Factors affecting the measurement accuracy of electromagnetic flow meters

一、Influence of test solution

1、The liquid to be tested contains bubbles

This is a common phenomenon. It is caused by external inhalation and internal liquid dissolution. However, electromagnetic flow meters cannot distinguish between liquids and bubbles, so calculation and measurement can cause errors.

2、The liquid to be tested is not full

It can be said that partially filled pipes contain bubbles. The liquid inside the tube is not full and there are a large number of bubbles at the top. If the liquid does not pass through the electrode, the measurement results of the electromagnetic flowmeter will be greatly reduced. This is an error in engineering design.

3、The conductivity of the measured liquid changes sharply

When the conductivity of the measured liquid is high, it will cause significant fluctuations in the displayed value.If the problem is serious, it is difficult for the control system to achieve normal operation; When the conductivity of the measured liquid is too low, it is difficult for the electrode to achieve normal output. If the conductivity of the measured liquid falls below the lower limit during operation, it will be difficult for the electromagnetic flowmeter to function properly. In response to these situations, firstly, based on actual needs, combined with relevant standards and requirements, choose the model of electromagnetic flow meter; Secondly, install a reactor or straight pipe section to ensure sufficient mixing of materials and promote the smooth implementation of chemical reactions; Thirdly, choose a new type of flow meter.

4、Space electromagnetic interference

Generally speaking, if the cable between the sensor and the converter is long and there is strong electromagnetic interference around, the cable may introduce interference signals and form Common-mode interference, resulting in distortion, nonlinearity or large jitter of the electromagnetic flowmeter.

二、Improper selection of model

1、Selection of electrode and lining materials

The electrode and lining material come into direct contact with the liquid to be tested. The electrode and lining materials should be selected based on the characteristics of the tested liquid (such as corrosiveness, abrasiveness, etc.) and working temperature. If selected improperly, it can cause problems such as rapid adhesion, corrosion, formation of dirt, wear, and deformation of the lining, which in turn can cause measurement errors in electromagnetic flow meters.

2、Excitation stability

The excitation methods for electromagnetic flow meters include DC excitation, AC sine wave excitation, and dual frequency square wave excitation. DC excitation is prone to electrode and DC interference issues. AC sine excitation can easily cause zero point changes, while dual frequency square wave excitation has excellent zero point stability with low-frequency square wave excitation, and high-frequency square wave excitation has strong ability to suppress fluid noise. This is an ideal excitation method. In practical applications, the power supply voltage and frequency should be as stable as possible to ensure constant magnetic field strength and reduce measurement errors caused by changes in magnetic field strength.

3、Measurement of mixed phase fluids

When measuring the flow rate of liquid-solid mixed phase fluids (such as water containing sediment) using an electromagnetic flowmeter, if a single-phase liquid calibrated electromagnetic flowmeter is used, measurement errors may occur.

■ Application scope

►  LC-A Type Cast iron oval gear flowmeter is widely used for measuring various oil products and liquids that do not corrode cast iron materials.

►  LC-E Type Cast steel oval gear flowmeter is used for measuring high-pressure and low corrosive liquid media.

►  LC-B、C Type Stainless steel oval gear flow meters are widely used for measuring highly corrosive liquid media such as acids, alkalis, salts, and organic compounds.