11
Figure 10. Probe length and measuring range
between the lower range value [4mA] and the upper range value [20mA] of the analog
current output is equal to 0...100% of your continuous level measurement reading. It is
recommended that the span between those two range values stays within the measuring
range [M].
For more details, please consult the section MEASUREMENT SPECIFICATIONS in page
13.
8
DISTURBANCE SIGNAL SCAN
The disturbance signal scan is a powerful disturbance signal suppression feature of
LTDR. The sensor scans its entire probe length for any disturbance signals in the
application that could potentially be misinterpreted as level readings, memorizes and
suppresses them during operation; that way LTDR only recognizes the actual level signals
caused by the liquid to be measured.
The disturbance signal scan is intended for the single rod probe and the rope probe, since
its signal has a wider detection radius around the rod, making it more responsive for
measurement signal disturbances.
The disturbance signal scan works most efficiently on stationary interference targets like
tall and narrow nozzles or close-by objects. Thus, LTDR has to be mounted in its final
position and the tank has to be completely empty in order to perform a disturbance signal
scan; that will ensure a reliable identification of the actual disturbance signals only. In
case that non-stationary interference targets close to the single rod probe, like slowly
rotating agitator blades or streams of liquid being filled into the tank, cause problems with
the measurement, it is recommended to use the coaxial probe.
Performing a disturbance signal scan is the prerequisite for utilizing this feature of LTDR.
