LW2720
Electronic level sensor
10
5.1.2 Foam and turbulence
Foaming liquids or turbulence may cause weak and varying echo amplitudes. Surface turbulence is
not normally a problem unless it is excessive.
Measurement in foamy applications depends largely on the foam properties. If the foam is light and
airy, the actual level is measured. For heavy and dense foam, the unit may measure the level of the
foam’s upper surface.
5.1.3 Influence of vessel characteristics and installation
The unit should be mounted so that objects such as heating coils, ladders and agitators are not in the
radar signal path. These objects may cause false echoes which can affect the measurement and lead
to measurement errors. However, the unit has built-in functions designed to reduce the influence from
disturbing objects where such objects cannot be totally avoided. Vertical and inclined structures cause
minimal effect since the radar signal is scattered rather than directed back to the antenna.
5.2 IO-Link
The unit has an IO-Link communication interface which requires an IO-Link capable module (IO-Link
master).
The IO-Link interface enables direct access to the process and diagnostic data and provides the
possibility to set the parameters of the unit during operation.
In addition, communication is possible via a point-to-point connection with a USB IO-Link master.
The IODDs necessary for the configuration of the unit, detailed information about process data
structure, diagnostic information, parameter addresses and the necessary information about the
required IO-Link hardware and software can be found at www.ifm.com.
5.3 Outputs
The unit generates output signals according to the parameter setting. Two outputs are available:
•
OUT1: switching output / IO-Link
•
OUT2: analogue output 4...20 mA or switching output (configurable)
5.3.1 Analogue output
The unit provides an analogue signal proportional to the level (according to NAMUR NE43, DIN IEC
60381-1) or a switching signal on output OUT2. The analogue output can be configured.
•
Parameter [ou2] = [I] sets output OUT2 as analogue output.
•
Parameter [ASP2] sets at which measured value 4 mA are provided.
•
Parameter [AEP2] sets at which measured value 20 mA are provided.
•
If [ASP2] is set lower than [AEP2], a rising curve results; if [ASP2] is set higher than [AEP2], a
dropping curve results (
Ò
Fig. Analogue output).
Minimum distance between [ASP2] and [AEP2] = 20 % of the active zone
