Overview – Solicap FTI55

• The Solicap FTI55 is a capacitance-based point level switch designed for solids (fine powders to coarse bulk materials).
• It belongs to the Solicap M series from Endress+Hauser.
• It is the rod version (FTI55); the rope version (for longer measuring lengths) is FTI56.

Official product page – Endress+Hauser

⚙️ Working Principle

• The FTI55 measures the capacitance change between its probe (rod electrode) and the vessel wall.
• When the bulk material covers the probe, the dielectric constant changes → the measured capacitance increases → the electronics switch state.
• Minimum detectable capacitance change (ΔC): ≥ 5 pF.
• Typical operating frequency: ~500 kHz.
• Available with fully or partially insulated probes, depending on the application.
• Includes active build-up compensation, allowing reliable operation even when material adheres to the probe surface.

Key Technical Specifications

Installation and Application Tips

1. Mounting guidelines
   • The probe must not touch the vessel wall (electrical isolation required).
   • Avoid direct installation in the filling stream (material falling directly on the sensor).
   • For non-metallic silos (plastic, fiberglass), add a metal counter-electrode plate outside the wall.
   • Ensure good grounding and shielding for stable capacitance measurement.
2. Calibration
   • Simple on-site calibration via push-button.
   • Calibration data stored in EEPROM — retained even if electronics are replaced.
3. Build-up compensation
   • Active compensation minimizes false switching from material deposits on the probe.
   • Regular cleaning still recommended for sticky or moist products.
4. Probe length selection
   • Choose length according to required switching point (high level, low level, etc.).
   • For low dielectric materials (εr < 2), sensitivity adjustments may be required.
5. Electrical protection
   • Equipped with two-stage surge and ESD protection.
   • In Ex environments, always follow specific wiring and grounding rules from the certification documents.

Typical Applications

• Point level detection in:
• Silos or bins with powders, granules, or pellets
• Cement, grain, plastic pellets, feed, sand, etc.
• Works well in dusty, abrasive, or sticky media.
• Can be used for both high-level and low-level detection.