1) Electromagnetic flowmeter need straight pipe that is shorter than ultrasonic flowmeter’s. Electromagnetic flowmeter installation site may no longer straight pipe, so compare at the scene, pay attention to the position of measuring whether can meet the requirements of straight pipe ultrasonic flowmeter, if does not meet the straight pipe should be nearby choose conforms to the position of the ultrasonic flowmeter measurement, comparison the results won’t be correct.
2) Check whether the installation position of the electromagnetic flowmeter meets the requirements of the liquid flow (such as the conductivity of the liquid, whether the installation is in the lower position of the pipeline, whether bubbles may accumulate, etc.). If not, it should be proposed to the user that this may be the cause of the problem.
3) Electromagnetic flowmeter is a good instrument to measure the flow of conductive liquid. Its measurement accuracy is also very high, generally in 0.5%, and it is best to reach 0.2%. At the same time, attention should be paid to the manufacturer of electromagnetic flowmeter. If the brand product is installed without error and the liquid conductivity meets the requirements, the measurement value should be carefully suspected, while for non-mainstream manufacturers, according to the electromagnetic field value stability and error size, you can be bold to doubt.
4) Understand the material condition of the pipeline, whether there is lining, scaling and other phenomena as well as related parameters of the pipeline from the user. Polish the pipeline when installing the ultrasonic sensor, and choose the Z method for measurement and comparison as far as possible.
5) The liquid that can be measured by the ultrasonic flowmeter is not affected by the conductivity. If the ultrasonic value is stable while the electromagnetic value is unstable during comparison, it indicates that the conductivity of the flow body being measured is in the boundary state of the index, rather than caused by the fluid containing gas, and the value of the ultrasonic flowmeter is credible. If both are unstable at the same time, the possibility of bubbles is greater.
6) electromagnetic flowmeter requirements to be measured liquid must be equal potential with the earth, otherwise there will be a strong interference measurement, so when the grounding is incorrect or bad grounding (electromagnetic grounding has more complex and strict requirements), there will be problems, should check the grounding situation. Compared with ultrasonic flowmeter, there is no potential requirement for liquid. If grounding is questionable, the value of ultrasonic flowmeter is correct.
7) If there are interference electric and magnetic fields nearby, the influence of ultrasonic flowmeter is less than that of electromagnetic flowmeter, and the reliability of ultrasonic display value should be greater than that of electromagnetic flowmeter.
8) If there is a interfering sound source in the pipeline (such as the sound generated by a large differential pressure regulating valve), the influence on ultrasonic is far greater than that on electromagnetic, and the reliability of electromagnetic indication value is greater than that of ultrasonic.
Post time: Jul-15-2022