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10.3. Self-diagnostics error messages
Self-diagnostics monitors the signal of the measure-
ment channel measuring the process and the signal of
device's internal reference channel. Self-diagnostics is
capable of detecting clear fault states, in which case it
generates an alarm by freezing the current signal or
setting it to 3.75 or 22.5 mA, according to user specific-
ations.
If, however, the fault is not a clear device fault but
rather measurement drifting, then self-diagnostics may
not necessarily be able to detect it. In such cases,
comparing self-diagnostics measurements with device
drifting and seeking correlations between these may
help in locating the source of the error.
Cab temp: Shows sensor electronics temperature. A
continuously high temperature reduces the average
fault interval. If the electronics temperature is continu-
ously over 75 degrees C, then it is recommended to
install the Vortex cooler in the sensor base plate. Refer
to chapter 11.7 for more information.
Mlev: Shows the measurement signal level in millivolts.
A decrease in measurement signal level below the
alarm level may be caused by an electronics failure,
antenna leakage, or high conductivity of the measured
pulp. If it is an electronics failure, then the reference
channel signal level Rlev is usually decreased to below
alarm limits.
Rlev: Shows the device's internal reference channel's
signal level in millivolts. A decrease in the signal level
to below alarm limits is always caused by a sensor
electronics failure.
Mstab: Mstab shows the stability of the measurement
channel signal. Stability reflects the effect of both
electronics and the measured pulp. Assuming that the
electronics are in order (see Rstab), you can determine
based on the Mstab value whether or not the process
contains large air bubbles that are causing measure-
ment errors. Large air bubbles cause both a rise in the
Mstab value as well as a temporary error in consistency
measurement. The level of the Mstab value is also af-
fected by consistency and sensor model. Fork Sensor
typically has a slightly higher Mstab value than FT
Sensor. Also, Mstab value is higher at a higher consist-
ency than at a lower consistency.
Rstab: Rstab shows the stability of the device's refer-
ence channel signal. The smaller the value, the more
stable the signal. An Rstab alarm is caused by sensor
electronic failure.
El drift: El drift value shows the drift in electronic delay
measured by the reference channel. This value is
compensated out of the measurement channel result,
so electronic drift does not cause an error in the
measurement result. An El drift alarm is caused by
sensor electronic failure.
VCO drift: VCO drift shows the drift in sensor electron-
ics signal generator. A VCO drift alarm is caused by
sensor electronic failure.
Installation & Owner’s manual OUL00298 V2.3 EN 43 Valmet Mircowave Consistency Transmitter