ABSTRACT
Based on Faraday's Law of magnetic induction, electromagnetic flowmeters, also known as ‘Magflows’ or ‘Magmeters’, have been in widespread use throughout industry for more than 40 years and were the first of modern meters to exhibit no moving parts and zero pressure drop.
Much of the initial discussion centres on the construction – the choice of lining materials and electrodes and the need for field characterisation. A close look is also taken at how measurement can be compromised by having only partially filled pipes and the steps that can be taken to overcome this problem – ranging from actual compensation through to empty pipe detection.
The problems of varying media conductivities were also examined – especially with regards to the measurement of ultrapure water.
The chapter concludes with a discussion on capacitive-coupled electrodes, the various proposals in terms of field excitation, and finally the use of insertion meters and the movement towards two-wire operation.
