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Agitated tank radar readings may rise and fall even when the average liquid quantity is nearly constant. Waves, a vortex, foam and moving internal reflectors can affect the observed distance. Increasing damping can make the trend look smoother while hiding a mounting problem or delaying a real level change.
Compare the oscillation with mixer operation
Record mixer state and speed with the radar distance and controller value. Where the process permits an authorised comparison, observe the tank under different normal mixer conditions. Do not stop required agitation merely to obtain a cleaner measurement trace.
A repeating pattern associated with mixer operation suggests a process or geometry relationship, but does not identify the cause by itself. Review the antenna position relative to the shaft, blades, inlet and likely surface depression. Save the original trend before changing response settings.
Where are agitated tank radar readings being filtered?
| Stage | Question to answer |
|---|---|
| Radar | What response or damping is configured in the instrument? |
| PLC input | Does the channel apply additional filtering or update slowly? |
| Control program | Is another averaging or rate-limiting calculation applied? |
| Trend display | Does the plotted trace average, compress or omit samples? |
Stacked filters can produce much more delay than the technician expects from the transmitter setting alone. Compare the time of a safely observed genuine level change at each stage. Use the response required by the process to judge whether the delay is acceptable.
The METRAVON MV-RD12 is a liquid radar with a nominal 8-degree beam. Evaluate its path through the nozzle and away from moving internals. The instrument's nominal distance accuracy does not describe the difference between a wave crest, vortex depression and the tank's average liquid surface.
Choose the correction from the cause
If the beam encounters a moving obstruction, assess a physical installation change. If the measurement follows a real fluctuating surface, determine what degree of averaging the operating duty can tolerate. If the local reading is reasonable but the PLC oscillates differently, inspect the downstream calculation or signal handling.
Do not validate a new damping value only at steady level. Check response during the relevant filling or emptying condition as well. A level trend used for slow inventory estimation and a signal used for rapid process action may need different treatment; neither should inherit a setting without review.
Q1. Can the indicated level be averaged until it stops moving?
Averaging reduces visible variation but can delay important changes. Select and verify the response against the actual operating requirement rather than a preference for a flat line.
Q2. Does the radar measure average tank volume through agitation?
It observes a reflecting surface within its beam. Converting that observation to volume requires tank geometry and consideration of whether the measured surface represents the intended inventory.
Summary
Relate oscillation to the mixer and signal path before adding damping. Share the MV-RD12 mounting drawing, mixer conditions and unfiltered observations for a targeted review.
