Compact vibrating fork level switch for liquids

Liquiphant FTL31

11-35 Pcs.


Compact version - right

Short tube version - left (available on request)

  • Robust stainless steel housing (316L)
  • Overfill prevention or pump protection
  • Onsite function check possible thanks to LED display




Vessels or pipes from DN25

Product density:

≥ 0.7 g/cm³

(>0.5 g/cm³ as option)

Product temperature:

-40 to +100 °C/+150 °C

Product viscosity:

≤ 10000 mm²/s

(10000 cSt)

Process pressure:

Max. 40 bar

Product/VersionPrice/pcs. in NZ$Order code
Liquiphant FTL31 - 10…30 VDC
Power Supply; Output
Electrical Connection / IP rating
Process Connection1 to 34 to 1011 to 35
10-30VDC; 3-wire PNPPlug M12, IP65/67Thread G1/2 BSP, 316L260.-242.-229.-FTL31-AA4M2AAWBJ
# Accessories1 to 34 to 1011 to 35
M12 right-angle plug with 4-core, 5m PVC cable30.-52010285

Prices are net, ex store Auckland, GST additional and valid until 30/9/2016.
EMC's standard Terms and Conditions of Supply are applicable.


The Liquiphant FTL31 is a point level switch for liquids and is used in tanks, vessels and pipes. It is used for overfill prevention or pump protection in cleaning and filter systems as well as in cooling and lubrication vessels, for instance. Ideal for applications in which float switches or conductive, capacitance and optical sensors have been used up to now. The Liquiphant FTL31 also works in areas where these measuring principles are not suitable due to conductivity, buildup, turbulence, flow conditions or air bubbles.


A piezoelectric drive causes the tuning fork of the Liquiphant FTL31 to vibrate at its resonance frequency. When the tuning fork is immersed in a liquid, its intrinsic frequency changes due to the change in density of the surrounding medium. The electronics system in the point level switch monitors the resonance frequency and indicates whether the tuning fork is vibrating in air or is covered by liquid. A signal is output via the DC-PNP electrical connection.

Application Example

The point level switch can be installed in any position in a vessel, pipe or tank, e.g., as overfill prevention or upper level detection (1), lower level detection (2) or dry running protection for pump (3)

Technical Data

DC-PNP version  (AC/DC version on request)
  • Supply voltage
10 to 30 V DC, 3-wire
  • Switching capacity
200 mA
  • Current consumption
<15 mA
  • Electrical connection

M12x1 (others on request)

Output general
  • Switching delay
0.5 s when tuning fork is covered

1.0 s when tuning fork is uncovered

  • Hysteresis
max. 3 mm
  • Process connection

Thread ISO 228 G½"

(others on request)

Operating conditions
  • Orientation
As required
  • Switch point
Vertical installation: 13 mm ±1 mm

Horizontal installation: 10.5 mm

(water +25 °C, 1 bar)

  • Pipe extension
103 mm (on request)
  • Surface roughness

Metallic surface in contact with process:

Ra ≤ 3.2 μm (126 μin)

  • Ambient temperature
–40 to +70 °C
  • Process temperature
–40 to +100 °C,

optionally to 150 °C

  • Process pressure

–1 to +40 bar

  • Storage temperature

–40 to +85 °C

  • Climate class
DIN EN 60068-2-38/IEC 68-2-38: test Z/AD
  • Density

>0.7 g/cm³ (optionally available: >0.5 g/cm³)

  • Viscosity
1 to 10000 mPa·s, dynamic viscosity
  • Degree of protection

IP65/67 NEMA Type 4X Enclosure (M12 connector)

  • Electromagnetic compatibility

Electromagnetic compatibility in accordance with all relevant requirements of the EN 61326 series and NAMUR recommendation EMC (NE21). For details, refer to the EC Declaration of Conformity.

  • WHG approval
Overfill detection system: Z-65.11-531
Leak detection system: Z-65.40-532

Dimensions (in mm) and material

Compact version

a) Thread ISO 228 G½"

b) Thread ISO 228 G1" (on request)


* Dimension for process temperature max. 100 °C

** Dimension for process temperature max. 150 °C


Installation according to instruction manual

Electrical connection

Electronic version 3-wire DC PNP

a) M12 connector

b) Valve plug (on request)

c) Cable (on request)

Technical Datasheet