Siemens SITRANS FMS500 - Design; Theory of operation

3.2 Design
The SITRANS FMS500 is an electromagnetic 󹪞ow sensor designed to meet the requirements in
ground water, drinking water, waste water, sewage or sludge applications. With its coned
design, increased low-󹪞ow accuracy is achieved making it especially useful for leak detection. It
is suitable for direct burial and constant 󹪞ooding. FMS500 complies with drinking water
approvals.
FMS500 compact version with FMT020 transmitter
(FM520)
FMS500 remote version
The sensors carry a wide range of approvals, see Technical speci󹪝cations (Page45).
3.3 Theory of operation
The 󹪞ow measuring principle is based on Faraday’s law of electromagnetic induction.
0DJQHWLF)LHOG
)ORZ
U
i
= When an electrical conductor of length L is moved at velocity v, perpendicular to the
lines of 󹪞ux through a magnetic 󹪝eld of strength B, the voltage U
i
is induced at the ends of
the conductor
U
i
= L x B x v
• U
i
= Induced voltage
• L = Conductor length = Inner pipe diameter = k
1
• B = Magnetic 󹪝eld strength = k
2
Description
3.3Theory of operation
SITRANS FMS500
14 Operating Instructions, 01/2024, A5E52677520-AA