KROHNE OPTISONIC 7060 EN - Manual (Page 16)

OPTISONIC 7060
Electrical & mechanical installation manual 730962.31.00 page 16 of 52
2.5 Self-diagnosis
In the measurement mode, the ratios of sound and path velocities, amplification settings,
and signal-to-noise are continuously monitored. If these parameters deviate from a preset
range, a warning signal is generated. This enables immediate measures to be taken to
prevent possible system malfunctions.
During commissioning or operation, you can adjust the signalling threshold values to suit
individual application requirements. This enables you to create the most effective status
warning system.
Note The "Warning" status signal does not affect the device function.
Parameter Default
threshold
value Warning
message Notes
Velocity of
sound < 5 m/s Warning SOS
Deviation This message is produced when the current measured path velocity of
sound deviates from the mean value of the mean velocities of sound
calculated for all the paths by more than the specified threshold value.
The current flow velocity is used as a weighting factor, so that
temperature stratification is disregarded at very low flow velocities. Used
to indicate whether or not the path is measuring the correct propagation
time.
Note
When setting the parameters, take into account plausible conditions for
normal operation (in particular temperature stratification).
< 6 dB Warning AGC
Deviation The absolute difference between both path gain factors is evaluated and
must remain below the threshold value.
Important
High flow rates can also increase the difference in gain.
Reception
gain
< 93 dB Warning AGC
Limit The absolute value of the reception gain is monitored.
Important
The current receiving sensitivity largely depends on the current process
pressure (inversely proportional in initial approximation, that is, when the
pressure doubles, the required receiving sensitivity is halved).
If one of the alarms is triggered by a path, this can indicate a malfunction
in the ultrasonic transducers, electronics, probe cables or parameter
settings (signal models, standard threshold values).
Signal-to-
noise ratio < 13 dB Warning SNR This alarm is activated when the signal-to-noise ratio is too small.
Reasons for this include interference noise caused by fittings in the
pipeline, valves that are not fully open, sources of noise near the
measuring location, or defective ultrasonic transducers.
Additional signal and system diagnosis functions monitor the accuracy of the measured
values, by checking the plausibility of the ultrasonic signals received and the ultrasound
signal propagation times calculated from them.