2
0
2
0
-1
1
54
Description of Sensor Parameters
8.4.3
Evaluation Method
The "Evaluation method" parameter allows you to specify the extent to which values of previous
measurements are included in the evaluation of the current measurement. The objective is to
ensure a robust measurement even when confronted with short-term disturbances such as
rain, compressed air, agitators, or wave formation on liquid surfaces.
Evaluation Methods in Practice
In most applications
the "Average value" setting
is proven to be effective. This involves cal-
culating a floating arithmetic average value over the latest data in accordance with the setting of
the "Averages & skip count" parameter.
When detecting a tank fill level where the liquid surface is heavily agitated, the
"Low pass"
setting
can be of benefit. With this evaluation method, previous data is included when deter-
mining the current distance value according to the "Weighting of former measurement",
"Allowed deviation to former measurement" and "Skip time" parameters. The evaluation pro-
duces a typical low pass behavior, i.e., the distance value output by the sensor follows the
actual measured value and the sensor response time is delayed accordingly. In addition, large
changes to the measured value are only taken into account if they occur repeatedly and/or after
a certain period of time.
With the
"None" setting
each individual measured value is output directly at the output. This
setting is not recommended for most applications as faulty measurements resulting from exter-
nal influences immediately have an effect on the output. When using the evaluation method, fil-
tering and/or validation of the data by downstream logic controllers (like a programmable logic
controller (PLC)) is recommended.
Note
This parameter is visible in the DTM advanced view.
Parameter name
Access
Value range
Evaluation method
Read/write
•
Average value
•
Low pass
•
None
Table 8.21
