Setting Data Filtering Parameters; Selecting Maximum Level Rate; Setting Up A Median Filter - ABB LWT300 Series User Manual

All these conditions are disabled by default. They are all enabled in a similar fashion, as explained
below:
1 Select Device Setup > Application Setup > Process Condition.
2 Highlight the relevant process condition and press Edit.
3 Highlight Enable and press OK.

Setting data filtering parameters

Processes can induce noise in level measurements. The LWT filtering feature is designed stabilize
measurements by filtering out extraneous data that could negatively impact the resolution of the
measured level (spikes, obstructions by mixer blades, lack of signal, etc.).
These parameters are set in the Filtering menu under the Device Setup menu.
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Figure 38 The Device Setup menu
The various filters available are applied in a sequence as follows:
Damping — Median filter — Max Level Rate — Amplitude Threshold

Selecting maximum level rate

The maximum level rate is the rate at which the process will reach its Full limit. This influences the
processing speed of the instrument. The default value is No Filter.
To set the maximum level rate:
1 Select Device Setup > Filtering > Max Level Rate.
2 Press Edit.
3 Highlight the appropriate maximum level rate and press OK.

Setting up a median filter

The median filter is designed to filter out noisy measurement spikes in applications with fast transients
(e.g., rapidly varying processes, positioning applications, etc). It is used for discarding occasional false
measurements resulting from any occasional unwanted phenomena that might occur in the process.
The value entered corresponds to the number of measurements kept in the buffer. The filter then
generates and returns a median value of all the measurements kept in the buffer. The buffer size can
range from 1 to 50 measurements. The default value is 1.
NOTICE
Selecting 1 measurement effectively disables the median filter as no averaging can be
performed.
Configuring the instrument
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