OPTISWITCH 3000 Series Vibration Level Switches

The OPTISWITCH series from KROHNE consists of compact vibration level switches designed for reliable point level detection of liquids and bulk solids.

• OPTISWITCH 3100 – universal stainless steel version for standard and hazardous areas (up to Zone 0/20).

• OPTISWITCH 3200 – with PFA coating for aggressive and corrosive media.

• OPTISWITCH 3300 – hygienic design for food & beverage and pharmaceutical industries (EHEDG, 3A).

Operating Principle

A piezoelectric element excites the tuning fork (or rod) to vibrate at its resonant frequency ≈ 1.4 kHz. When the sensor comes into contact with liquid or bulk solid, the amplitude and frequency of vibration change. The integrated electronics instantly detect this change and generate a switching output (relay, transistor, or NAMUR). The measurement is completely independent of conductivity, density, foam, or product build-up.

General Technical Specifications

All models feature a compact stainless steel housing with IP66/67 protection rating, power supply 10–30 V DC or 90–253 V AC, and power consumption less than 1 W. Process temperature range: –50 °C to +250 °C (model-dependent); pressure from vacuum up to 100 bar. Insertion length: 80 mm to 6 m (with cable extension). Wetted materials: stainless steel 1.4404/1.4571, optional PFA coating or polished surface Ra < 0.76 µm for hygienic applications. Outputs: relay (SPDT/DPDT), transistor (Puls), NAMUR, frequency, optional HART or IO-Link. Switching accuracy ±1 mm, response time < 0.5 seconds. Explosion protection: ATEX, IECEx, FM, CSA (up to Zone 0/20). Hygienic certifications (3300 only): EHEDG, 3A, FDA-compliant materials.

Main Application Areas

• Chemical, petrochemical, and oil & gas industries (aggressive liquids)

• Power generation, water and wastewater treatment (pump dry-run protection, overfill prevention)

• Food & beverage, dairy, and pharmaceutical industries (hygienic level monitoring)

• Bulk solids storage (grain, cement, plastic pellets, powders)

Advantages of OPTISWITCH Vibration Level Switches

• No moving parts → virtually maintenance-free

• Immune to product build-up, condensation, and external vibration

• Works with very low density media (liquids ≥ 0.5 kg/m³, solids ≥ 20 g/l)

• Fast response and excellent repeatability

• Simple installation and commissioning (one-button or no adjustment required)

• High level of explosion protection and hygienic certification

• Extremely long service life (MTTF > 50 years)

• Compact design and low total cost of ownership