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
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Parameter
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Typical Value / Range
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Process temperature
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–50 °C … +180 °C
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Process pressure
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Vacuum … +25 bar
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Probe length
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200 mm … 4000 mm (≈ 8 in … 157 in)
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Housing materials
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Aluminum, polyester, or stainless steel
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Repeatability
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± 0.1 %
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Supply / output
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Multiple electronics versions (AC, DC, relay, PNP/NPN, etc.)
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Explosion protection
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Versions available with ATEX / FM / CSA approvals
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Installation and Application Tips
- 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.
- Calibration
- Simple on-site calibration via push-button.
- Calibration data stored in EEPROM — retained even if electronics are replaced.
- Build-up compensation
- Active compensation minimizes false switching from material deposits on the probe.
- Regular cleaning still recommended for sticky or moist products.
- 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.
- 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.
