Home
Cart

Cart

product added to request

Get an offer

Full name*

E-Mail*

telephone*

Company*

street*

place*

zip code*

country*

additional information

I agree that my details and data are collected and stored electronically in order to answer my enquiry.

Your cart

22 article(s) in your cart
pos.	image	product	Configure	Actions
1		QFS-55
2		TK-301
3		DS-CAN-01
4		ZDT-H
5		ZMF-202e-IR
6		T209-0.F
7		TRM-100
8		Ex-BK
9		TK-101 EX
10		EFV2 24V
11		T202
12		TK-315
13		KS-210 KS-220
14		ES-20
15		LU-180 EX
16		TK-300
17		EE-2XF
18		T204-0.F
19		HD-100 \| HD-102 \| HD-104
20		ViscoScope® VA-300
21		LU-1X0
22		T205-0

QFS-55 configure

1 Ausführung

2 Kontakt

3 Schaltkontakt

4 Kabelmaterial

5 Kabellänge

6 Ex-Option

Amount

additional infomation

TK-301 configure

1 Material Rohr und Verschraubung

2 Gewinde

3 Ausführung

4 Schwimmerausführung

5 Anschluss

6 Rohrlänge

7 Auflösung

8 Zubehör

Amount

additional infomation

ZMF-202e-IR configure

1 Typ

2 Temperaturbereich

3 Messmethode

4 Signalausgang

5 Messbereich

6 Ex-Zulassung

Amount

additional infomation

TRM-100 configure

1 Material

2 Measuringrange

3 Connection

4 Flange

5 Sealing

Amount

additional infomation

Ex-BK configure

1 Ex

Amount

additional infomation

TK-101 EX configure

1 ATEX

Amount

additional infomation

EFV2 24V configure

1 Sicherheitsfunktion

2 Verstellbar

3 Elektrodenanzahl

4 Verschraubungsmaterial

5 Stabmaterial

6 Anschluss

7 Anschlussgewinde

8 Kabelbruchwiderstand

9 Auswerteelektronik

10 Standaufnehmerlänge

11 SIL

Amount

additional infomation

TK-315 configure

1 Gehäuse

2 Eingang

Amount

additional infomation

ES-20 configure

1 Measurand

2 Safety-Function-1

3 Safety-Function-2

4 Direction

5 Measuringrange

6 Channel-Expansion

Amount

additional infomation

LU-180 EX configure

1 Typ

Amount

additional infomation

TK-300 configure

1 Rohr-Verschraubungsmaterial

2 Gewinde

3 Ausführung

4 Schwimmerausführung

5 Anschluss

6 Rohrlänge

7 Auflösung

8 Zubehör

Amount

additional infomation

EE-2XF configure

1 Typ

2 Elektrodenanzahl

3 Anschlussgewinde

4 Stabmaterial

5 Stabdurchmesser

6 Beschichtung

7 Kabelbruchwiderstand

8 Sicherheitsfunktion

9 Stablänge

Amount

additional infomation

HD-100 | HD-102 | HD-104 configure

1 Gehäuse

2 Messbereich

3 Ausgangssignal

4 Kabelart

5 Kabellänge

6 Abdichtung

7 Sondermesszelle

Amount

additional infomation

ViscoScope® VA-300 configure

1 Viscosity

2 Temperature

3 Process-Connection

4 Material

5 Non-active-Extension

6 Ex-Bereich

Amount

additional infomation

LU-1X0 configure

1 Typ

Amount

additional infomation

QFS-55

Teflon float switch in rod design

The float switch combination is built with float switches of the QFS-50 and QFS-60 series. This makes it possible to control a level in a simple way.

Technical Data

Material : PTFE (Teflon)
connection cable : Silikon, Teflon
Material rod : VA-Rohr, PTFE beschichtet
Operating temperature : max. +150 °C
media density : ρ ≥ 0,75 g/cm³
Switching system : Reed-Schalter
Contact : Wechsler, NO, NC
Inductive/capacitive loads : Unbedingt Kontaktschutz vorsehen
Ex-protection optional : Elektrische Daten siehe EG-Prüfbescheinigung IBExU10ATEX 1089

Reed contact

Switching current : 1 mA ... 1 A
Switching voltage : 24 ... 250 V AC/DC
Switching capacity : Max. 1A, 60 VA / 60 W
Switching hysteresis : ca. 100 mm
Switching angle : ca. +20°...–20°

Namur circuit (1kΩ/12kQ)

Switching current / switching voltage : nur zum Anschluss an KR-163... oder andere „Namur”-Relais
Switching hysteresis : ca. 100 mm
Switching angle : ca. +20°...–20°

TK-301

Liquid Level Measuring Instruments Series

T30... continuous magnetic immersible probes are used for quasi-acquisition of the filling level in containers with liquid media.

Technical Data

connection : Dose
Protection class socket / plug : IP 65
Protection class EN60529 cable : IP 55
Float type : 05 (06)
connection cable : 1000 mm Silikon 0,5 mm²
Sliding tube length : max. 6000 mm
Operating temperature : max. 130 °C
Operating pressure : max. 20 bar
Resolution : 7,5 mm | 10 mm | 15 mm | 20 mm| 1 % | 2 % | 5 %
Accessories : R/I-Wandler TK-101

MaterialDensity

Type 05 : 0,81 g/cm³
Type 06 : 0,67 g/cm³

DS-CAN-01

CANopen pressure transmitter with CAN bus signal output

Versatile, media-compatible pressure transmitter with CAN bus interface.

technical properties

Pressure type : Relativdruck gegen Umgebungsdruck bzw. gegen interne Atmosphäre
measuring resolution : 10 Bit
Measuring accuracy : Klasse 0,5 bei RT
Total error : < 1,5 % v.E bei -10 °C … +80 °C.
measuring grid : ab 5 ms
CAN protocol : CANopen 2.0 A
Physical Layer : nach DIN 11898

ambient conditions

Operating temperature range : -40 °C … +80 °C
Storage temperature range : -40 °C … +120 °C
Shock resistance : 30 g, Dauer
Vibration resistance : 10 g bei 20-1000 Hz
EMC/ESD : EN 50082-1 und EN 50082-2
Duration : 14 ms bei RT

Pressure measuring ranges

kPa : bar
0...500 : 0…5
0...1.000 : 0…10
0...2.000 : 0…20
0...5.000 : 0…50
0...10.000 : 0…100
0...35.000 : 0…350
0...50.000 : 0…500
0...70.000 : 0…700
0...200.000 : 0…2.000
0...400.000 : 0…4.000
Standard pressure range : in kPa
Non-standard ranges : auf Anfrage erhältlich

ZDT-H

Differential pressure transmitter for high pressure applications

Versatile and reliable differential pressure transmitter for measuring air, non-aggressive media as well as liquids and oils.

Properties

Pressure type : Differenzdruck
Housing : Kunststoff mit LCD-Anzeige (oponal)
Overpressure : 1,2* (1,5*) x Nenndruck

Measurement parameters

Total error : ± 2,5 % FS (typ. ± 0,5 %)
Linearity error : ± 1 % FS
Signal output selection : 0...10 V 4...20 mA, 2-Leiter 4...20 mA, 3-Leiter
Pressure range : 5…1.000 bar

Operating conditions

Operating voltage : 14...28 VDC ± 10 %
Operating temperature : 0...+50 °C
Storage temperature : -20°C...+120°C

Connections

Electrical connection : Schraubklemme im Gehäuse
Process connection : G1/4" (andere auf Anfrage)

ZMF-202e-IR

Robust propane gas sensor for industrial applications with extended operating temperature range and ATEX / SIL-2

The ZMF-202e-IR is a propane sensor for measuring propane concentration in harsh environments.

Properties

Operating conditions : -40 °C…+60 °C
Storage conditions : -40 °C…+85 °C
RelativeHumidity : 0…95 % nicht kondensierend
Measurement method : NDIR (dual beam technology)
Certification : SIL2, ATEX
Signal output : 4..20mA
Power supply : 12…24 V DC
Housing : Edelstahl
Standard cable length : 1,5 m
pressure conditions : 800...1200 mbar
screw thread : M46x1,5

Measuring ranges

in ppm : in vol%
0...17.000ppm : 0…1,7 vol% (100 % LEL)
0...21.000ppm : 0…2,1 vol%

Options

Other cable lengths on request :
ATEX certification (optional) :

T209-0.F

Magnetic immersion probe overfill protection for Ex zone 0 (Cat. 1)

The magnetic immersion probes T20... are used to detect fill level limit values in containers for liquid media, where an explosive atmosphere of zone 0 (cat. 1) is present in the gas space above the liquid and Ex zone 1 (cat. 2) is present outside the container, in the area of the junction box.

Properties

connection : Polyesterdose, Aluminiumdose
Protection class : IP 65 Dose
Float type : Kugel Edelstahl 105 mm Ø
Sliding tube length : max. 6000 mm
Operating temperature : max. 135°C
Operating pressure : max. 20 bar
media density : 0,54 g/cm³
F-Contact : 1 / 12 kΩ
Number of additional contacts : 6x Wechsler, 9x Schließer, 6x Öffner
Switching current : 1A, 2A ( nur mit Schirmung)
Switching capacity : Wechsler: 60 W/VA, Schließer: 100 W/VA Öffner: 60 W/VA
min. contact distance with several floats : 125 mm

TRM-100

Turbidimeter (0...1.000 FNU or 500...4.000 FAU)

The turbidimeter TRM-100 is a compact device for measuring turbidity in liquids. The "turbidity" is measured using the scattered light method (angle 90 degrees) for the turbidity range of < 1,000 FNU (Formazine Nephelometric Units) and the transmitted light method (angle 0 degrees) for the turbidity ranges > 1,000 FAU (Formazine Attenuation Units).

Properties

Operating pressure : max. 10 bar @ 20 °C | max. 2,5 bar @ 60 °C
Measuring range : 500...4.000 FNU / FAU
Measuring accuracy : +/-5 %
Mounting position : horizontal
Process connection : DN 20 | DN 40
Flange connection : >= DN 20
number of senders : 2
number of receivers : 1

Material

Seal : EPDM | optional FPM (Viton)
Process connection : PVC | PPH
Measuring tube : Borsilikatglas mit Nano Beschichtung

Input

Power supply : 18...30 V DC
Power consumption : < 2 W

Output

Output contact : 4...20 mA
Switching delay (adjustable) : 1...10 s
Protection class : IP 65
Switching voltage : max. 250 V AC | max. 115 V DC
Switching current : max. 3 A
Switching capacity : max. 500 VA, 60 Watt
Potential-free changeover contact : 1 @ 1...10 s

Ex-BK

Bistable change-over contact

Magnetically actuated changeover switch, which permanently changes its electrical switching state as a result of a magnetic system passing by, depending on the direction of movement.

Properties

Protection class EN60529 : IP 65
Operating temperature : –20...+120 °C
Wire cross-section max. : 1,5mm²
Switching point distance between two contacts : min. 40 mm
Switching hysteresis : ca. 10-15 mm
Dimensions : 80 mm x 75 mm x 57 mm

Material

Housing : Aluminium
Mounting clip : V2A
Rivet : V2A
Screw connection : M 20 x 1.5, V2A

Weight

BK-390-50 : 137 g
BK-390-63 / BK-380 : 140 g

Switching contact

Switching voltage : 24...250 V AC/DC
Switching current : 20 mA...6 A AC/DC
Switching capacity(min.) : max. 500 VA, 60 W
Switching capacity(max.) : min. 2 VA/W

TK-101 EX

Measuring transducer (R/I-transducer)

The measuring transducer Tk101 and Tk101Ex are built directly into the connection boxes of our Liquid Level Measuring Instruments of type TK-30.

Properties

Operating temperature : -20...+60 °C
Storage temperature : -40...+80 °C
Ex-protection : siehe Zertifikat
CE marking : siehe Konformitätserklärung

Input

Resistance range in three-wire circuit : 4...10 kΩ
Measuring current : 0,8 mA @ RE = 4 kΩ
Measuring current : 0,33 mA bei RE = 10 kΩ
Measuring voltage : 3,3 V

Supply/Output

2-wire : 4...20 mA
Voltage(Um) : 11...28 V DC
Burden / load : 0...800 Ω |RBürde max = [(Um - Um min) / 0,02] Ω
Output signal in case of error : max. 24 mA

Fault influences

Max. Total error : ± 1 %
Temperature influence : -0,015 % / °C
Supply voltage influence : 0,025 % / V

Setting range

Full deflection : 60...105 %
Zero point adjustment : 0...25 %

EFV2 24V

adaptive conductive electrodes with and without 24 V direct connection

The conductive electrode EFV2 is approved by the "DIBt" as an overfill prevention device for liquids hazardous to water.

Connection

Box : Polyesterdose (PO)
Cable : Kabel (TPK)
Plug : Stecker (ST)

Properties

Protection class : IP 65
connection thread : G2"
Union nut : G2¾", S 100x8
Material Screw connection : PE, PVC, PPH, PVDF
Material Sensor rods : Edelstahl (1.4571), Hastelloy C, Titan, Tantal, Kohlestifte
Operating temperature : PE, PVC: atmosphärisch PPH : 90 °C, PVDF: 100 °C
Operating pressure : atmosphärisch
Resistance value of line monitoring : 22 kΩ / 100 kΩ je nach Ausführung

Operating temperature

PE : atmosphärisch
PVC : atmosphärisch
PPH : 90 °C
PVDF : 100 °C

Technical specifications electronic part

Operating temperature : –20...+85 °C
Storage temperature : –30...+85 °C
nominal voltage : 24...30 V DC
Power consumption : max. 2 W
Switching voltage : max. 230 V AC / V DC min. 5 V DC (CMOS-Relais)
Switching current : max. 0,12 A AC / A DC min. <1 mA
Switching capacity : max. 25 VA / W
Sensitivity : 3k … 100 kΩ

T202

Immersible Magnetic Probe made of stainless steel (1.4571)

Magnetic immersion probes for use with highly aggressive liquid media for detecting level limits in containers

Properties

connection : Polyesterdose | Aluminiumdose
Protection class EN60529 : IP 65 Anschlussdose
Connector plug : 3- und 6-fach
connection thread : G 1/8" | G 3/8" | G 1/4" | G 1/2" | G 1" | G1 1/4" | G1 1/2" | G2" | G3"
connection cable : LiYY max. 80 °C | PTFE-Litze, 0,24 mm² | Silikon max. 150 °C
Sliding tube length : max. 1000 mm (Rohr Ø 8 mm) | 6000 mm
Operating pressure : max. 20 bar
Viscosity : < 100 cp
Protection class EN60529 : IP 68 Führungsrohr
Switching voltage : max. 250 V
Switching hysteresis : ca. 2...5 mm
Holding range : ca. 12 mm
Contact function : monostabil | bistabil

Operating temperature

ltdata. : max. +60...+150 °C
ltdata. : min. –20... –10 °C
ltdata. : höhere oder niedrigere Temperaturen auf Anfrage

Switching capacity

Changeover contact : 60 W/VA
normally open : 100 W/VA
Normally closed contact : 60 W/VA

Switching current

Changeover contact : max. 1 A
NO/NC contact : max. 2 A

Contacts

Changeover contact : 8
normally open : 10
Normally closed contact : 7

TK-315

Evaluation unit with 4 limit contacts (NO-contacts)

The TK-315 limit comparator can be used in conjunction with our TK-30... continuous level sensors with 0(4)...20 mA or 0...10 V output signal for level control/measurement.

Properties

Protection class EN60529 clamp : IP 20
Protection class EN60529 front panel housing : IP 40
Operating temperature : –20...+60 °C
nominal voltage : 24... 230 V AC/DC
Power consumption : 2 VA
Dimensions housing type B : 22,5 x 114,5 x 99 mm
Dimensions housing type C : 22,5 x 114,5 x 114 mm

Input

power : 0/4...20 mA
Voltage : 0...10 V
Resistance in three-wire circuit RG : 0–4...10 kΩ

Output

Output contacts : 4 Schließerkontakte
Switching voltage : max. 250 V AC
Switching current : max. 3 A
Switching capacity : max. 500 VA
Temperature influence tolerance : max. ± 0,6 % der Signalspanne
Mounting : Tragschiene nach EN 50022
Current output : 4...20 mA bezogen auf die Masse des Eingangs
Display (%) : 2-stellig, 7-Segment
Weight : 175 g

KS-210 KS-220

Compact sensors for temperature & humidity measurement

The KS series sensors are modular temperature and humidity measurement sensors in compact housings for use in almost any application.

Properties KS-210

Operating voltage : 12...30V DC
Power consumption : < 15mA

Properties KS-220

Operating voltage : 24V DC
Loop voltage min: : Bürde(Ohm) *0,02 + 8 V
Loop voltage max: : 30V

General properties

Housing : Aluminium, eloxiert
Dimensions (in mm) : 135 x Ø 19,2

Measuring range

measuring range (Humidity) : 0…10% rH
Measuring accuracy (humidity) : ± 2%
measuring range (Temperature) : -40...+80°C
Measuring accuracy (temperature) : ± 0,2°C
Signal output : 0...10V | 4...20mA

ES-20

Pressure limiter | Pressure monitor | Safety pressure limiter | Pressure regulator | electronic safety switching device

TÜV-certified, type-tested electronic safety switching device (SIL2)

Properties

Operating voltage : 16...32 V DC (max. 5,9 W)
Dimensions : 150 x 60 x 42 mm (L x B x H)
Housing : Aluminium (eloxiert)
Protection class : IP65

Approvals

DGRL 2014/68/EU Kat:IV : Baumustergeprüft gemäß Druckgeräterichtlinie
DIN EN12263:1998 : Kälteanlagen und Wärmepumpen Sicherheitsschalteinrichtungen zur Druckbegrenzung -Anforderungen und Prüfungen; Kategorie IV
DIN EN378:2020 : Kälteanlagen und Wärmepumpen - Sicherheitstechnische und umweltrelevante Anforderungen
DIN EN61508:2011 : SIL2

Operating conditions

Pressure type : Relativdruck, Differenzdruck
Temperature of the fluid : -40…+125 °C
Ambient temperature : -20…+65 °C
Parts in contact with media : Edelstahl

Connections

Process connection Relative pressure (internal thread) : G ¼“
Process connection differential pressure (internal thread) : G ⅛“
Analogue current output : 1 x 4...20 mA
Digital inputs/outputs (configurable) : 2 x Alarm / 1 x Alarm & 1 x Fernentriegelung

Measuring range relative pressure

Nominal pressure (variable selectable) : -1...500 bar
Overload pressure : 2 x Nenndruck
Bursting pressure : 4 x Nenndruck
Setting accuracy : 0,1 % vom Nenndruck

Measuring range differential pressure

Nominal pressure : 0...1 mbar 0...10 mbar 0...50 mbar 0...100 mbar 0...250 mbar 0...1.000 mbar
Overload pressure : 10 x Nenndruck
Bursting pressure : 15 x Nenndruck
Setting accuracy : 0,1 % vom Nenndruck

LU-180 EX

Compact Ultrasonic Level Sensor

The LU-150 is a short-range integrated ultrasonic level transmitter, intrinsically safe as Ex-version LU-180. This general purpose, 2 wire, 4 to 20 mA loop powered transmitter is ideal for liquids, slurries, and bulk materials in open or closed vessels to 5 m (16.4 ft).

Properties

Protection class EN60529 : IP 68
Power supply : 12...30 V DC / 0.1A Spitze
Power consumption : Max. 0,75 W (25 mA bei 24 V DC)
Output : 4...20 mA
Max. Load : 600 Ω bei 24 V DC
Measuring span : Proportional oder umgekehrt proportional
Measurable materials : Flüssigkeiten, Schlämme, Schuttgüter
operating temperature : –20...+60 °C
Opening angle : 12°
working pressure : Atmosphärisch
Display : 3-stelliges LCD
Process connection : Gewinde G 2" (BSPP) EN 10226 PVDF
Weight : 1,3 Kg
Cable entry : Kabelverschraubung M 20 x 1.5
Material housing electronics : Polybutylenterephthalat PBT
Material sensor / thread : PVDF-Copolymer

Input

Measuring range : 0,25...5,0 m
frequency : 54 kHz

Measuring Accuracy

Measurement deviation : ± 0,25 % vom Messbereich (in Luft)
Resolution : 3 mm
Temperature compensation : im Sensor integriert
Echo processing : „Sonic Intelligence“ von Siemens

TK-300

Level transducer

T30... continuous magnetic immersible probes are used for quasi-acquisition of the filling level in containers with liquid media.

Properties TK-300

connection : Polyesterdose | Aluminiumdose | Stecker nach DIN 43650
Protection class socket / plug : IP 65
Protection class EN60529 cable : IP 55
Float type : 10 (14)
connection cable : 1000 mm LiYY 0,5 mm² oder Silikon 0,5 mm²
Sliding tube length : max. 6000 mm
Operating pressure : max. 6 bar
Resolution : 10 mm, 15 mm oder 1%, 2%, 5% je nach Auflösung
CE marking : siehe Konformitätserklärung

Operating temperature

PV : max. 60°C
PE : max 80 °C
PP : max. 90°C

MaterialDensity

Type 10 : 0,72 g/cm³
Type 14 : 0,72 g/cm³
Type 18 : 0,82 g/cm³

EE-2XF

Conductive electrodes as overfill protection for Ex-Zone 0 (Cat. 1)

Conductive electrodes EE-2XF for monitoring conductive liquids within the Ex area Zone 0 (Cat. 1) for water-polluting and flammable liquids.

Properties

connection : Edelstahl (1.4571)
Protection class : IP 65
Ex-protection : TÜV 02 ATEX 1796 X
Ex protection type : II 1 G Ex ia IIC T6 bzw. Ex ia IIB T6 / II ½ G Ex ia IIC T6 bzw. Ex ia IIB T6
connection thread : G1", G1¼", G1½”
Coating length : voll=ganzer Stab (10 mm am Stabende sind blank) teil =ca. 250 mm von oben
Rod diameter : 4 oder 6 mm
rod length : max. 6 m
Operating pressure media side : max. 40 bar
Maximum permissible electrical connection values : Stromkreis in Zündschutzart Eigensicherheit Ex ia IIC/IIB
Connection values : Ui 15V | Li 10 mA | Pi 100 mW
Internal inductances / capacitances : vernachlässigbar klein
Spacer : ab Länge > 1000 mm je 1000 mm 1 Abstandshalter

Operating temperature

Category 1 Class T6...T1 : 60 °C
Category 2 Class T6 : Medien & Umgebung 80 °C
Category 2 Class T5 : Medien & Umgebung 95°C
Category 2 Class T4 : Medien 130°C, Umgebung 100°C
Category 2 Class T3...T1 : Medien 150°C, Umgebung 100 °C

Material

Cable entry EE-21 : Edelstahl (1.4571)
Cable entry EE-22 : PVDF
Electrode body material : Edelstahl (1.4571)
Seal (head) : Viton
Seal (media side) : Viton / PTFE
Potential equalisation conductor connection : Edelstahl (1.4571)
Material electrode rods : Edelstahl (1.4571), Hastelloy B, Hastelloy C, Tantal
material coating : PTFE

T204-0.F

Immersible Magnetic Probe for Ex Zone 0 (Cat. 1)

The T20... magnetic immersion probes are used to detect fill level limits in containers for liquid media, where an explosive atmosphere of Zone 0 (Cat. 1) exists in the gas space above the liquid and an Ex-Zone 1 (Cat. 2) exists outside the container in the area of the junction box.

Properties

connection : Kabel PUR blau
Protection class : IP 68 Dose
number of floats : max. 4x
Operating temperature : max. 135 °C
F-Contact : 1 / 12 kΩ
Number of additional contacts : max. 3x Wechsler | 5x Schließer | 3x Öffner
Switching current : 1 A, 2 A (nur mit Schirmung)
Switching voltage : 230 V AC

Float

Stainless steel ball 61 mm Ø : max. 20 bar | 0,65 g/cm³
min. contact gap type 04 : 85 mm

Switching contacts and switching capacity

Changeover contact : max. 3x | 60W/VA
normally open : max. 5x | 100 W / VA
Normally closed contact : max. 3x | 60 W/VA

HD-100 | HD-102 | HD-104

Hydrostatic immersion probes (0.8...10mWS)

Continuous and precise level measurement in unpressurised, open basins and tanks as well as underground applications such as shafts, wells and boreholes.

Properties

Protection class EN60529 : IP68
Operating temperature : -10...70 °C (PVC: -10...60 °C)
Storage temperature : -25...70 °C (PVC: -10...60 °C)
Power supply : 15...30 V DC
power : max. 25 mA
Output : 2-Leiter-Technik
Measuring range : 0,8...10 mWs (Standard)
Overpressure : abhängig vom Messbereich
Deviation from characteristic curve : Nichtlinearität,
Insulation resistance : > 100 kΩ
Short-circuit resistance : permanent
Reverse polarity protection : keine Schädigung o. Funktion bei vertauschten Anschlüssen