Managing Lost Echoes; Preventing Unnecessary Alarms; Setting Up Linearization; Understanding Linearization - ABB LWT300 Series User Manual

Managing lost echoes

A lost echo happens when your instrument loses the signal returning to the sensor. You can set the
parameters that help your instrument manage such situations.
Period
The lost echo period is the time period during which the instrument waits before reacting.
To set a lost echo period:
1 Select Device Setup > Safety Setting > Echo Lost Period.
2 Press Edit.
3 Set the period of time for lost echoes and press OK.
Reaction
You can configure the instrument reaction when echoes are lost for the set period of time: hold the last
value measured or raise an alarm.
To do so:
1 Select Device Setup > Safety Setting > Echo Lost Reaction.
2 Press Edit.
3 Highlight the necessary reaction and press OK.

Preventing unnecessary alarms

During operation, the instrument might encounter alarm-raising, but very temporary, conditions (e.g.,
sporadic EMC interference). To prevent raising unnecessary alarms, you can configure an alarm delay
that will let a specified amount of time pass before raising an alarm.
To set such a delay:
1 Select Device Setup > Safety Setting > Alarm Delay.
2 Press Edit.
3 Set a value (between 0 and 3600 seconds; the default is 10) for the delay that you want to allow
before the instrument raises alarm and press OK.

Setting up linearization

In your LWT instrument, the linearization function allows more accurate level, volume and flow
measurements by referring to a preset linearization table.

Understanding linearization

Linearization is especially useful in irregularly shaped vessels (cylindrical lying tanks, spherical gas tanks,
etc.), but in all applications, regardless of vessel shape, it is used to convert media level to a linearized
level, or volume or flow.
The linearization table provides the instrument with data regarding known volumes at specific levels in
the irregularly shaped part of a vessel.
Below is an example of the relationship between a linearization table actual measured levels:
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User Guide