ABB FSM4000 Series, Operating Instruction

Page: 98 / 136

98 FSM4000 ELECTROMAGNETIC FLOWMETER | OI/FSM4000-EN REV. E
… 8 Operation
… Additional information regarding use of enhanced diagnostic functions
Determining the coil temperature
The coil temperature is a factor of the ambient and fluid
temperatures. The measurement can be for example used to
monitor overtemperature through the medium.
The coil temperature is measured indirectly via the coil DC
resistor (ABB Patent GB 2 348 011).
To perform the measurement, you need to power-up one of the
relevant errors or a warning in the submenu ‘Diagnostics / Alarm
Settings’ (see
Alarm Settings on page 85).
T
Coil
=
C
R
R R
f f
f Coil
° +
•
−
20
Re Re
Re
α
T
Coil
Coil temperature
R
Coil
Coil resistance
R
Ref
Reference coil resistance at 20 °C
f Re
α
Temperature coefficient of copper at 20 °C (0.39 %/K)
Note
The coil resistance of the flowmeter sensor must be adjusted for
a reference temperature. This applies to newly shipped systems
consisting of SE41F / SE21 and S4. When connecting an S4
transmitter to previously shipped SE41F / SE21 sensors, you
need to additionally perform the adjustment. For more
information in this regard, see
Readjusting the coil temperature
on page 106.
Determining the insulation resistance for the coil
Figure 56
Detecting problems with the coil insulation. Can be caused, e.g.,
by dampness in the flowmeter sensor or in the connection box.
When determining the insulation resistance of the coil to
ground, a DC field test signal of approx. 1 sec is sent to the coil,
separating the ground connection in the transmitter. In spite of
the separation provided by the coil, the current flowing to
ground is used to calculate the insulation resistance.
During this measurement, the flowrate cannot be measured and
the most recent value is retained.
To perform this test, you need to power-up one of the relevant
errors or warnings in the submenu ‘Diagnostics / Alarm Settings’
(see page
Alarm Settings on page 85).