Liquipoint T FTW31

Summary

Product Identification

• Product Name: Liquipoint T FTW31, FTW32
• Type: Conductive Point Level Switch
• Application: Multiple point detection in conductive liquids (minimum conductivity of 10 µS/cm). Suitable for overfill protection, dry running protection, and two-point pump control.

Key Features

• Detects up to five point levels with a single probe.
• Supports two-point control with additional MAX and MIN detection capabilities.
• Available in rod (FTW31) or rope (FTW32) versions.
• Flexible instrumentation options:
  • Integrated electronic insert with transistor (PNP) or relay output.
  • Connection to a separate transmitter power supply unit.
• No adjustment required for common conductive liquids.
• No moving parts, ensuring long service life and reliable operation.
• WHG approval.

Measuring Principle

The device operates by measuring the change in resistance between probe rods caused by the presence or absence of conductive liquid. An alternating voltage is applied to the probe rods. When a conductive liquid bridges the gap between the ground rod and another probe rod, a measurable current flows, triggering the switch. This AC voltage prevents probe corrosion and electrolytic damage.

Measuring System Options

The measuring system can consist of:

• Probes without integrated electronic insert (Separate Instrument Version):
  • FTW31 (rods) or FTW32 (ropes) with 2, 3, or 5 rods/ropes.
  • Paired with a Nivotester FTW325 switching unit for one to five point detection.
  • Compatible with control units, switches, or signal transmitters (e.g., PLCs, relays).
• Probes with integrated electronic insert (Compact Instrument Version):
  • FTW31 (rods) or FTW32 (ropes) with an integrated electronic insert.
  • Directly connectable to control units, switches, or signal transmitters.

Input

• Measured Variable: Resistance change between conductors due to the presence or absence of conductive liquid.
• Measuring Range (Application):
  • Rod probes: Maximum length of 4 m (13 ft).
  • Rope probes: Maximum length of 15 m (49 ft).
• Input Signal:
  • Probes covered: Measurable current flows.
  • Probes uncovered: No measurable current flows.

Output Options

Electronic Insert FEW52 (DC-PNP)

• Output Signal: Three-wire DC, PNP output. Positive signal at the switch output.
• Fail-safe Mode: MAX or MIN fail-safe. Output voltage is 0 V under fault conditions or when the switch point is exceeded (MAX) or undershot (MIN).
• Switching Delay: 2.0 s (can be activated/deactivated via DIL switch) or approx. 0.3 s if not activated.
• Sensitivity: Adjustable in four levels (100 Ω, 1 kΩ, 10 kΩ, 100 kΩ). Default setting: 100 kΩ.
• Load: Switched via transistor (PNP), continuously rated 200 mA, short-circuit proof. Residual voltage <2.9 V.
• Supply Voltage: 10.8 V to 45 V DC.
• Power Consumption: < 1.1 W.

Electronic Insert FEW54 (Relay)

• Output Signal: Two potential-free change-over contacts.
• Fail-safe Mode: MAX or MIN safety. Relay de-energizes when the switch point is exceeded (MAX), undershot (MIN), or during a fault/power failure.
• Switching Delay: 2.0 s (can be activated/deactivated via DIL switch) or approx. 0.3 s if not activated.
• Sensitivity: Adjustable in four levels (100 Ω, 1 kΩ, 10 kΩ, 100 kΩ). Default setting: 100 kΩ.
• Load Capacity:
  • AC: max. 253 V / 4 A, max. 1000 VA (cos  = 1), max. 700 VA (cos  > 0.7).
  • DC: max. 30 V / 4 A, max. 150 V / 0.2 A.
• Supply Voltage: 20 V to 55 V DC or 20 V to 253 V AC (50/60 Hz).
• Power Consumption: < 2.0 W.

Electronic Insert FEW58 (NAMUR)

• Output Signal: For connection to isolating amplifiers according to NAMUR (IEC 60947-5-6). Output signal jumps from high to low current (H-L edge) at point level.
  • Normal: 2.2 to 6.5 mA.
  • Alarm: 0.4 to 1.0 mA.
• Fail-safe Mode: MAX or MIN safety. Output signal <1.0 mA during fault conditions or when the switch point is exceeded (MAX) or undershot (MIN).
• Switching Delay: 2.0 s (can be activated/deactivated via DIL switch) or approx. 0.3 s if not activated.
• Sensitivity: Adjustable in four levels (100 Ω, 1 kΩ, 10 kΩ, 100 kΩ). Default setting: 100 kΩ.
• Supply Voltage: Refer to the technical data of the connected isolating amplifier.
• Signal on Alarm: < 1.0 mA (damaged sensor).

Cable Monitoring

Available for separate instrumented probes (requires a printed circuit board). This feature is mandatory for probes with WHG certification.

Performance Characteristics

• Reference Operating Conditions: Ambient temperature 23 °C, medium temperature 23 °C, 0 bar pressure, vertical installation.
• Measuring Error: ±10 % (100 Ω - 100 kΩ), ±5 % (1 kΩ - 10 kΩ).
• Non-repeatability: ±5 % (100 Ω - 100 kΩ), ±1 % (1 kΩ - 10 kΩ).
• Hysteresis: -10 % for MAX probe (Δs function disabled).
• Switch-on Delay: < 3 s.
• Influence of Ambient Temperature: < 0.05 %/K.

Installation

• Mounting Location: Predominantly in tanks; can be used in partially filled piping for applications like pump dry running protection (two-rod probes).
• Orientation: Vertical mounting is standard. Lateral mounting is possible for MAX detection with two-rod probes (max. probe length 200 mm).

Environment

• Ambient Temperature Range:
  • Non-hazardous area: –40 to 70 °C (–40 to 158 °F).
  • FEW58 (NAMUR): –40 to 60 °C (–40 to 140 °F).
• Storage Temperature: –40 to 80 °C (–40 to 176 °F).
• Climate Class: Tropicalized as per DIN IEC 68, part 2-38.
• Degree of Protection: IP66.
• Shock Resistance: Practical test.
• Vibration Resistance: 20 to 2000 Hz, 1 (m/s²)²/Hz (at minimum rod length).
• Electromagnetic Compatibility:
  • Interference Emission: EN 61326, Electrical Equipment Class B.
  • Interference Immunity: EN 61326, Annex A (Industrial).
  • Screened cable recommended for separate-instrumented probes.

Process

• Conductivity: ≥ 10 µS/cm.
• Limiting Medium Pressure Range: –1 to 10 bar (–14.5 to 145 psi).

Mechanical Construction

• Materials:
  • Wetted parts: EPDM seals, PP spacer, elastomer fiber seals, PPS process connections, 316L or carbon fiber probe rods, PP insulation for rods, 316Ti probe ropes, FEP insulation for ropes.
  • Non-wetted parts: PPS or PBT housing, PBT-FR or PA12 covers.
• Probe Rods:
  • Diameter (uninsulated): 4 mm (0.16 in).
  • Length: 100 mm to 4000 mm (3.94 to 157 in).
• Rope Probes:
  • Diameter (uninsulated): 1 mm (0.04 in).
  • Length: 250 mm to 15000 mm (9.84 to 591 in).
• Weights: Varies based on configuration (e.g., Separate instrument version, 1m rod probe: 415 g to 760 g).

Human Interface

• Operating Elements: DIL switches for fail-safe mode, switching delay, and sensitivity settings.
• Display Elements: LEDs on compact instrument versions (red for fault/status, green for operation). Separate instrument versions rely on the display of the connected switching unit.

Certificates and Approvals

• CE Mark: Complies with EC directives.
• Overfill Protection: WHG approval.
• Other Standards: Low Voltage Directive, DIN EN 61010, EN 61326.
• RoHS: Complies with Directive 2011/65/EU.
• RCM-Tick Marking: Meets ACMA requirements.
• Ex-Approvals: Specific data in separate Ex documentation.
  • [EEx ia] IIC (FEW58)
  • [EEx na/C(L)] IIC (FEW52, FEW54)

Ordering Information

Detailed ordering information is available via the Endress+Hauser website Product Configurator or from sales centers.

Accessories

• Lock nut G 1 1/2"
• Electronic insert FEW52 (PNP)
• Electronic insert FEW54 (Relay)
• Electronic insert FEW58 (NAMUR)

Documentation

• Operating Instructions: KA00204F/00
• Certificates: WHG (ZE00043F/00), ATEX (XA00226F/00, XA00230F/00)

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Disclaimer: This extraction may miss figures, footnotes, or revisions. Contractual data must match the OEM PDF revision used on the project.

Official datasheet (PDF)

Lenntech datasheet mirror