KROHNE LS 4100 EN User Manual
Page 3
03/2002
LS 4100/LS 4150
3
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1.1
Function and configuration
LS 4100/LS 4150 detect levels of liquids with a viscosity of 0.2 up to 10.000 mPa s and a density
of
≥
0.6 g/cm
3
. Modular construction enables their use in machines, plants, vessels and pipelines,
even in applications severely limited in space. Typical applications are overfill and dry run
protection.
LS 4100 is optionally available with threads G 1 A and 1" NPT. The stainless steel housing
(1.4571) is in protection class IP 67.
LS 4150 is mainly suitable for level detection in the food processing and pharmaceutical industry.
Due to the polished sensor surface (Ra
≤
0.5 µm or Ra
≤
1.5 µm) bacteria have no chance to
collect. LS 4150 is also suitable for CIP and SIP cleaning. Many different hygienic fittings such as
cone with compression nut, Tri-Clamp 1" and 2", bolting, Tuchenhagen VARIVENT or special
hygienic connections are available.
Due to the simple and rugged measuring system, LS 4100/LS 4150 is virtually unaffected by the
chemical and physical properties of the liquid. They work even under unfavourable conditions
such as turbulence, air bubbles, foam generation, build-up or varying products. An adjustment to
the medium is not necessary.
The electronics can be exchanged without problems. LS 4100/LS 4150 must not be removed.
LS 4100/LS 4150 has an integrated test switch which can be activated magnetically. It tests the
sensor electronics and the connected instruments.
1.2
Principle of operation
The tuning fork is piezoelectrically energised and vibrates at its mechanical resonance frequency
of approx. 400 Hz. This frequency is transferred to the electronics of LS 4100/LS 4150. When the
tuning fork is submerged in the product, the frequency changes. This change is detected by the
integrated oscillator and converted into a switching command.
By changing of poles of the supply voltage, the switching condition can be defined (max.
detection/min. detection). With the transistor version, PNP or NPN action can be preset by a
different connection of the consumer (load).
The integrated fault monitoring detects:
•
interruption of the connection cable to the piezo elements
•
extreme wear on the tuning fork
•
break of the tuning fork
•
no vibration
If one of the stated failures is determined or in case of voltage loss, the electronics takes on a
defined switching condition, e.g. the output transistor blocks.