10.3. Self-diagnostics error messages
The self-diagnostics monitors the signals of the process
measurement channel and the internal reference
channel. This system is able to detect clear device
faults. When such a fault occurs, the system gives an
alarm by either freezing the signal or by setting it to a
user-selected value, either 3.75 or 22.5 mA.
However, if the measurement result drifts but no
obvious device failure is observed, the self-diagnostics
system may not be able to detect the situation. In such
cases it may be useful to compare the self-diagnostics
measurement results to the observed drift, and to look
for any correspondences between these, in order to
locate the fault.
Cab temp: Temperature of sensor electronics. If this
temperature is continuously very high, faults are likely
to occur more frequently.
Mlev: Measurement signal level, mV. If the measure-
ment signal level drops below the alarm limit, the
reason may be either an electronics fault, an antenna
leak, or very high conductivity of the measured sludge.
In case of an electronics fault, usually also the refer-
ence signal level Rlev has dropped below the alarm
limit.
Rlev: Signal level of the internal reference channel,
mV. If this signal level drops below the alarm limit, the
problem is always in the sensor electronics.
Mstab: Indicates the stability of the measurement
channel signal; this reflects the effect of both sensor
electronics and the measured sludge. If the sensor
electronics is OK (see Rstab), the Mstab value indicates
if the process contains large air bubbles that may cause
measurement errors. Large air bubbles cause a higher
Mstab value, and too high total solids content results.
The Mstab level is also influenced by the total solids
content, and sensor model. When the total solids con-
tent is high, the Mstab value is higher than for lower
solids contents.
Rstab: Stability of the internal reference channel signal.
The lower this value, the more stable the signal is.
Rstab alarm is caused by a fault in sensor electronics.
El drift: Indicates the drift in the electronics delay
measured by the reference channel. This value is
eliminated from the measurement channel by compens-
ation, and thus any electronics drift will not cause errors
in the measurement result. The El drift alarm is caused
by a fault in sensor electronics.
VCO drift: Indicates the drift of the signal generator in
the sensor electronics. This alarm is caused by a fault
in sensor electronics.
Installation & Owner's manual, OUL00489 V2.3 EN
35
Valmet Total Solids Transmitter
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