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Brand: KOBOLD
KOBOLD NWS Tuning Fork Liquid Level Switch, up to 45 bar
Description
Tuning fork level switch with no moving parts for liquids
The KOBOLD NWS is a liquid level switch that works on the tuning fork principle. In air, a piezoelectric crystal excites the fork at its resonance frequency and monitors it; when the fork is immersed in a liquid the frequency changes, the electronics detect this and the output switches. It has no moving parts and is insensitive to plant vibration, with a repeatability of ±1 mm, a maximum pressure of 45 bar and a maximum medium temperature of 130 °C.
The NWS is a 2-wire or 3-wire switch for vessels and pipelines, usable as an upper or lower limiter through a mode selector. An LED seen through the cover shows the state: it is permanently on when the switch is on and flashes about once a second when it is off, which also confirms that the fork is working. KOBOLD names oils and foamed oils, water, paints, milk and liquids containing carbon dioxide as applications, and cleaning in place up to 150 °C.
Technical specifications
| Parameter | Specification |
|---|---|
| Principle | Tuning fork (piezoelectric excitation), upper or lower limit by mode selector |
| Repeatability / hysteresis | ±1 mm / 4 mm vertical, 1 mm horizontal |
| Minimum medium density / viscosity | 800 g/l / up to 5000 mm²/s at 25 °C |
| Maximum pressure | 45 bar (flange connections follow the pressure steps) |
| Medium temperature | -20 to +130 °C (NWS-…200); -20 to +90 °C (other versions); short-time 150 °C for CIP |
| Ambient temperature | -20 to +70 °C |
| Materials | Fork and process connection stainless steel 1.4404; electronics housing stainless steel 1.4301 or PAG with window (NWS-…200) |
| Process connections | R ¾ and R 1 male, ¾” and 1″ NPT, DN 25 and DN 50 flanges, 1″ and 2″ ANSI 300 lb flanges, Tri-Clamp DN 40 / DN 50, DIN 11851 DN 40 / DN 50, aseptic DIN 11864 DN 50, DRD flange |
| Supply, version 200 | 2-wire 24 to 240 VAC (50/60 Hz) or 24 to 40 VDC, load up to 400 mA; 3-wire 24 VDC PNP |
| Supply, versions 23 and 24 | 24 VDC, 3-wire, PNP (23) or NPN (24), M12 plug (S) or 1.5 m cable (F) |
| ATEX / IECEx (NWS-…2E) | II 1G Ex ia IIC T6 Ga; IECEx Ex ia IIC T6 Ga; needs an isolation switching amplifier to IEC 60947-5-6 (Namur) |
| Switching delay | 1 s wet to dry and 1 s dry to wet |
| Protection | IP65 (version 200); IP68 (23, 24); IP67 (2E) |
| Sensor length | Standard; extended 117, 300, 500 or 1000 mm, or special 140 to 3000 mm on marked models |
Output versions and connections
Version 200 has a plastic housing with cable gland and terminals for universal 24 to 240 VAC/DC supply, working as a 2-wire switch in series with the load (voltage drop about 5 V) or as a 3-wire PNP switch. Versions 23 and 24 use stainless steel housings with an M12 plug or cable for 24 VDC PLC inputs. The ATEX version 2E is intrinsically safe and must be used with a Namur isolation switching amplifier such as the KFD2-SR2-EX1.W or KFA6-SR2-EX1.W named in the datasheet.
The hygienic connections (Tri-Clamp, DIN 11851 and DIN 11864) suit food, beverage and pharmaceutical lines. The minimum immersion depth for a switch point is 12 mm, marked on the fork, and horizontal mounting gives a smaller hysteresis than vertical mounting.
Ordering the NWS
The order example is NWS-R20 200 0070: connection and model (R20, R25, N20, N25, F25, F50, A25, A50, T40, T50, L40, L50, H50, D1Z or special), electrical version (200, 23S, 24S, 2ES, 23F, 24F or 2EF) and sensor length. Extended sensors are available only on the models marked with an asterisk in the datasheet.
Confirm before ordering: the liquid density against the 800 g/l minimum, viscosity, temperature against the 130 °C or 90 °C limit, supply and output type, and whether a Namur amplifier is already in the cabinet for Ex versions.
Documents and quotation
The KOBOLD NWS datasheet (edition 1/03-2025) is attached to this page. Browse our Level Instrumentation category for related instruments, or compare with the VEGA VEGASWING 61 vibrating level switch.
For a quotation, send the connection type and size, electrical version, sensor length, liquid, density and viscosity, temperature, pressure and any hazardous-area requirement.
Datasheets & Documents
- Datasheet KOBOLD NWS tuning fork level switch datasheet Download
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About brand
KOBOLD Messring GmbH is a German instrumentation manufacturer based in Hofheim am Taunus, founded in 1980 by Klaus J. Kobold. It develops and manufactures instruments for monitoring, measuring and regulating flow, pressure, level and temperature, and the international KOBOLD group of companies serves virtually all sectors of industry.
KOBOLD flow and level instruments
The KOBOLD range covers Coriolis, thermal mass, magnetic inductive, turbine, oval gear, oscillation and variable area flow meters and flow switches, together with guided wave radar, 80 GHz radar, magnetostrictive, tuning fork and bypass level instruments. Many models carry ATEX or IECEx approvals, and several offer HART, Modbus or IO-Link communication.
Requesting KOBOLD instruments from Seven Star LLC
Seven Star LLC, an independent supplier in Muscat, lists selected KOBOLD flow and level instruments for oil and gas, water, power and process plants in Oman and the GCC. Send the model code, measuring range, process connection and approvals needed, and Seven Star LLC will prepare a quotation from the KOBOLD datasheet.
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Frequently Asked Questions
What is the KOBOLD NWS used for?
Point level detection in liquids such as oils, water, paints, milk and carbonated liquids, in vessels and pipelines.
What pressure and temperature does the NWS handle?
Up to 45 bar; medium temperature up to 130 °C on version 200 and up to 90 °C on other versions, with short-time 150 °C for CIP.
Is the NWS affected by plant vibration?
KOBOLD states it has no moving parts and is insensitive to plant vibrations.
Which supply options are available?
Version 200 takes 24 to 240 VAC or 24 to 40 VDC as a 2-wire switch; versions 23 and 24 are 24 VDC PNP or NPN 3-wire.
Is there an ATEX version of the NWS?
Yes. The 2E version is marked II 1G Ex ia IIC T6 Ga with an IECEx equivalent and needs an isolation switching amplifier to IEC 60947-5-6.
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