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7.4.1.7
Determining the signal-to-noise ratio
1
1 Signal from flowmeter
sensor
2 Filtered signal
7.4.1.8
Determining the magnetic linearity
ML =
Determining the maximum DAC value
7.4.1.9
D184B140U02
x
x
x
x
-1
Z
2
+
+
G00578e
I
U
R
G00578f
I
U
1
R
2
I
U
2
R
1
Driver
1011
U
ref
G00578g
Detect changes in fluid, e.g., gas bubbles, increased/reduced
amount of solids.
To determine the signal-to-noise ratio (SNR), the electrode AC
voltage - raw signal for the flowmeter sensor is set in relation to
the digitally filtered signal.
Filtered
signal
SNR =
Signal
from
flowmeter
The SNR is measured without impairing the flow measurement
in any way. To perform this calculation, it is necessary to switch
on one of the relevant errors or warnings in the submenu
"Diagnostics / Alarm Settings" (see page 82).
Detect magnetic field interference. This can affect the accuracy
of the measurement.
When measuring magnetic linearity (ML), the coil current I
measured at current reference voltage U
approximately half the reference voltage U
The operating time at half the reference voltage is approx. 1
sec. During this period, the most recently acquired value is
retained.
To perform this test, it is necessary to switch on one of the
relevant errors or warnings in the submenu "Diagnostics/Alarm
Settings" (see page 82).
For detecting changes in the coil circuit.
To compensate the set reference voltage Uref, the level of the
digital/analog converter (DAC) value is manipulated in the
transmitter's driver circuit to vary the coil's excitation signal. The
amplitude of this value then serves as an indicator of the level
of the excitation signal.
The DAC value is measured without affecting the flow
measurement in any way.
To perform this measurement, it is necessary to switch on one
of the relevant errors or warnings in the submenu
"Diagnostics / Alarm Settings" (see page 82).
FSM4000
Parameterization
sensor
and coil current I
R1
.
R2
is
1
at
2
91
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