
LNK
Page 4 LNK K06/0422
5. Operating Principle
The conductive KOBOLD level probes LNK together with the transducer for head
mounting or the external evaluating electronic are used for level detecting. This
method is based on the evaluation of the electrical conductivity of the medium. In
combination with the KOBOLD LZE or LZE-R weld-in sleeves, the probe provides
a measuring point that has no dead space and meets hygiene standards
(EHEDG approval certificate). This level switch is therefore ideally suited for
CIP/SIP cleaning.
The level switch is available with 1 or 2 - 4 electrodes. As an option, they can be
delivered with an E-CTFE coating. This allows foaming media to be detected
reliably.
The output signal from the probes with head mounted transmitter can be
connected directly to a PLC for evaluation. This means lower installation costs,
minimum wiring requirements and a high degree of noise immunity.
The device is available with an optional M12x1 plug connector.
5.1. Head transmitter LNR (Option LNK-...NPK, LNK-...NPS)
A usage of the head transmitter LNR is only possible, when the LNK as a 2-
stem probe, contains an earth stem and a monitoring stem.
The transmitter integrated in the electrode head provides a control voltage
between the detecting electrode and the earth electrode. When the electrodes dip
into a conductive liquid, a small alternating current starts flowing. An integrated
switching amplifier detects this alternating current and switches the
24 VDC active output accurately, as soon as an adjusted trigger threshold is
crossed. When the liquid drops below the limit value electrodes, the output
becomes inactive again.
5.2. External electrode relay (e.g. NE-104, 304)
When the LNK is used as a 3-stem or 4-stem probe (2 or 3 switching points), the
evaluation takes place with an external electrode relay (see instruction manual
and technical details of the external electrode relay).
In order to get an additional switching point, the electrically conductive and
grounded vessel wall can be used as ground terminal. Therefore the ground
electrode can be used as an additional switching electrode.