Endress+Hauser Liquiphant FTL31 User Manual

Point level switch for liquids

Application

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.

The Liquiphant FTL31 can be used for process temperatures up to:

• 100 °C (212 °F)

• 150 °C (302 °F)
Not suitable for hazardous areas.

The use of the Liquiphant FTL33 is recommended for hygiene areas.

Your benefits

• Operational safety, reliability and universal application thanks to the tuning fork
measuring principle

• Robust stainless steel housing (316L)

• External function test with test magnet

• Onsite function check possible thanks to LED indication

• Compact design for easy installation even in confined conditions or hard-to-access
areas

Products Solutions Services

Technical Information

Liquiphant FTL31

Vibronic

TI01147F/00/EN/02.14
71267728

Liquiphant FTL31

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Table of contents

Document information ....................... 3

Document conventions .......................... 3

Function and system design ................... 4

Measuring principle ............................ 4

Measuring system ............................. 4

Input ..................................... 5

Measured variable ............................. 5

Measuring range .............................. 5

Output ................................... 5

Switch output ................................ 5

Operating modes .............................. 5

Power supply .............................. 5

Supply voltage ............................... 5

Power consumption ............................ 5

Current consumption ........................... 5

Residual ripple ............................... 5

Electrical connection ........................... 6

Electronic version 3-wire DC-PNP ................... 7

Electronic version 2-wire AC/DC ................... 9

Overvoltage protection ......................... 10

Performance characteristics .................. 11

Reference operating conditions ................... 11

Switch point ................................ 11

Hysteresis ................................. 11

Non-repeatability ............................ 11

Influence of ambient temperature ................. 11

Influence of medium temperature .................. 11

Influence of medium pressure .................... 11

Switching delay .............................. 11

Switch-on delay ............................. 11

Measuring frequency .......................... 11

Measured error .............................. 11

Installation ............................... 12

Orientation ................................ 12

Installation instructions ........................ 12

Length of connecting cable ...................... 14

Environment .............................. 15

Ambient temperature range ..................... 15

Storage temperature .......................... 15

Climate class ............................... 15

Altitude ................................... 15

Degree of protection .......................... 16

Shock resistance ............................. 16

Vibration resistance ........................... 16

Electromagnetic compatibility .................... 16

Reverse polarity protection ...................... 16

Short-circuit protection ........................ 16

Process .................................. 17

Process temperature range ...................... 17

Process pressure range ......................... 17

Density ................................... 17

State of aggregation ........................... 17

Viscosity .................................. 17

Solids contents .............................. 17

Lateral loading capacity ........................ 17

Mechanical construction .................... 18

Design .................................... 18

Connector ................................. 19

Tuning fork ................................ 19

Sensor type ................................ 20

Weight ................................... 23

Materials .................................. 23

Surface roughness ............................ 23

Operability ............................... 24

LED display ................................ 24

Function test with test magnet .................... 24

Certificates and approvals ................... 25

CE mark ................................... 25

C-Tick symbol ............................... 25

Approval .................................. 25

Overfill prevention ............................ 25

Marine approvals ............................ 25

CRN approval ............................... 25

Inspection certificates .......................... 25

Manufacturer declarations ...................... 25

Pressure Equipment Directive .................... 25

Other standards and guidelines ................... 25

Ordering information ...................... 26

Product Configurator .......................... 26

Services (optional) ............................ 26

Accessories ............................... 27

Weld-in adapter ............................. 27

Plug-in jack, cable ............................ 27

Additional accessories ......................... 28

Supplementary documentation ............... 29

Operating Instructions ......................... 29

Additional documentation ...................... 29

Certificates ................................. 29

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Document information

Document conventions Safety symbols

Symbol Meaning

DANGER

A0011189-EN

DANGER!

This symbol alerts you to a dangerous situation. Failure to avoid this situation
will result in serious or fatal injury.

WARNING

A0011190-EN

WARNING!

This symbol alerts you to a dangerous situation. Failure to avoid this situation
can result in serious or fatal injury.

CAUTION

A0011191-EN

CAUTION!

This symbol alerts you to a dangerous situation. Failure to avoid this situation
can result in minor or medium injury.

NOTICE

A0011192-EN

NOTE!

This symbol contains information on procedures and other facts which do not
result in personal injury.

Electrical symbols

Symbol Meaning

A0011200

Ground connection

A grounded terminal which, as far as the operator is concerned, is grounded via a grounding
system.

A0011199

Protective ground connection

A terminal which must be connected to ground prior to establishing any other connections.

Symbols for certain types of information

Symbol Meaning

A0011182

Permitted

Indicates procedures, processes or actions that are permitted.

A0011184

Forbidden

Indicates procedures, processes or actions that are forbidden.

A0011193

Tip

Indicates additional information.

A0011194

Reference to documentation

Refers to the corresponding device documentation.

A0011195

Reference to page

Refers to the corresponding page number.

Symbols in graphics

Symbol Meaning

1, 2, 3 ... Item numbers

A, B, C, ... Views

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Function and system design

Measuring principle

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 or AC/DC electrical connection.

Measuring system

The measuring system consists of a Liquiphant FTL31 point level switch, e.g. for connection to
programmable logic controllers (PLC), a mini-contactor or solenoid valve.

2

1

3

A0020911

1 Overfill prevention or upper level detection MAX (maximum safety)
2 Lower level detection MIN (minimum safety)
3 Lower level detection MIN, e.g. dry running protection for pump

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Input

Measured variable

Density

Measuring range

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

Output

Switch output

Switching behavior: On/Off

Function

3-wire DC-PNP:
Positive voltage signal at the switch output of the electronics (PNP), switching capacity 200 mA
2-wire AC/DC:
Load switching in the power supply line, switching capacity 250 mA

Operating modes

The device has two operating modes: maximum safety (MAX) and minimum safety (MIN).

By choosing the corresponding operating mode, the user ensures that the device also switches in a
safety-oriented manner even in an alarm condition, e.g. if the power supply line is disconnected.

• Maximum safety (MAX)
The device keeps the electronic switch closed as long as the liquid level is below the fork. Sample
application: overfill prevention

• Minimum safety (MIN)
The device keeps the electronic switch closed as long as the fork is immersed in liquid. Sample
application: Dry running protection for pumps

The electronic switch opens if the limit is reached, if a fault occurs or the power fails (quiescent
current principle).

Power supply

Supply voltage

DC-PNP:
AC/DC:

10 to 30 V DC, 3-wire
20 to 253 V AC/DC, 2-wire

Power consumption

DC-PNP:
AC/DC:

< 975 mW
< 850 mW

Current consumption

DC-PNP:
AC/DC:

< 15 mA
< 3.8 mA

Residual ripple

DC-PNP:
AC/DC:

5 Vss 0 to 400 Hz
—

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Electrical connection

Two electronic versions and three different connections are available for the device. A fine-wire fuse
is necessary for operation: 500 mA slow-blow.

Cable entry

A

B

C

A0020928

A Valve plug (M16x1.5; NPT ½"; QUICKON)
B M12 connector
C Cable 5 m (16 ft); 10 m (33 ft), captive when delivered, cannot be dismantled

Cable specification

• Valve plug
– Cable cross-section: max. 1.5 mm2 (AWG 16)
– Ø 3.5 to 8 mm (0.14 to 0.26 in)

• M12 connector: IEC 60947-5-2

• Cable (3LPE)
– Cable cross-section: 0.75 mm2 (AWG 20)
– Ø 6 to 8 mm (0.24 to 0.31 in)
– Material: PUR

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Electronic version 3-wire DC­PNP

3-wire DC-PNP is preferably used in conjunction with programmable logic controllers (PLC), DI
modules as per EN 61131-2. Positive signal at the switch output of the electronics (PNP).

Voltage source: non-hazardous contact voltage or Class 2 circuit (North America).

M12 connector

Depending on the analysis of the switch outputs, the device works in the MAX (maximum safety) or
MIN (minimum safety) mode.

A cable is optionally available for order, see "Accessories" section (→  27).

Electrical connection Operating mode

M12 connector MAX MIN

A0022901

0.5A

L– L+

2

1

3

4

K

A0022858

0.5A

L–

L+

2

1

3

4

K

A0022859

1

21

2

A0021416

1

41

4

A0021417

K

Yellow LED (ye) not lit
Yellow LED (ye) lit
external load

Function monitoring with M12 connector

Using a two-channel analysis, function monitoring of the sensor can be implemented in addition to
level monitoring, e.g. per relay switch, PLC, AS-i Bus I/O module, …).

When both outputs are connected, the MIN and MAX outputs assume opposite states when the
device is operating fault-free (XOR). In the event of an alarm condition or a line break, both outputs
are deenergized.

Connection for function monitoring with antivalence

Yellow LED

(ye)

Red LED

(rd)

0.5A

L– L+

2

1

3

4

K1

K2

A0022917

Sensor covered

1

2

1

4

A0023016

Sensor exposed

4

1

1 2

A0023029

Fault

21

41

A0023030

K1 / K2

LED lit
LED not lit
Fault or warning
external load

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Valve plug, cable

Depending on the assignment of the connector or the wiring of the cable, the device works in either
the MAX or MIN operating mode.

Electrical connection Operating mode

Valve plug MAX MIN

A0022900

1

3

0.5A

L–

L+

2

K

+

–

A0021724

L–

L+

3

0.5A

1

2

K

+

–

A0021723

3

23

2

A0021413

2

32

3

A0021414

Cable (cannot be
dismantled)

0.5A

1

2

3

L–

L+

K

+

A0022226

L+

0.5A

K

1

2

3

L–

+

A0022227

A0022902

Core colors:
1 = BK (black)
2 = GR (gray)
3 = BN (brown)
Ground = GNYE (green­yellow)

3

23

2

A0021413

2

32

3

A0021414

K

Yellow LED (ye) not lit
Yellow LED (ye) lit
external load

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Electronic version 2-wire
AC/DC

The load is switched via an electronic switch directly in the power supply circuit. Always connect in
series with a load!

Not suitable for connection to low-voltage PLC inputs!

Selection tool for relays

2.7

2.5

2.3

2.1

1.9

1.7

1.5

1.3

1.1

0.9

0.7

0.5
20 24 27 43 48 53 60 110 121 207 230 253

P/S

U

P1

P2

A0023486

 1 Minimum rated power of the load

P/S Rated power in [W] / [VA]
U Operating voltage in [V]

Position Supply voltage

Rated power

min max

P1
AC mode

24 V
110 V
230 V

> 1.3 VA
> 1.5 VA
> 2.5 VA

< 6 VA
< 27.5 VA
< 57.5 VA

P2
DC mode

24 V
48 V
60 V

> 0.7 W
> 0.9 W
> 1.5 W

< 6 W
< 12 W
< 15 W

Relays with a lower rated power can be operated by means of an RC module connected in parallel
(optional).

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Valve plug, cable

Depending on the assignment of the connector or the wiring of the cable, the device works in either
the MAX or MIN operating mode.

When the cable is wired, one wire of the cable does not have any function in each of the operating
modes (brown in the case of MIN, and gray in the case of MAX). The cable with no function must be
secured against inadvertent contact.

Electrical connection Operating mode

Valve plug MAX MIN

A0022900

3

0.5A

1

K

>20 V

L1/L+ N/L–

A0021219

2

0.5A

1

K

>20 V

L1/L+ N/L–

A0021220

1313

A0021418

1212

A0021420

Cable (cannot be dismantled)

3

L1/L+

0.5A

K

>20 V

1

2

N/L–

A0022161

1

L1/L+

0.5A

K

2

3

N/L–

>20 V

A0022225

A0022902

Core colors:
1 = BK (black)
2 = GR (gray)
3 = BN (brown)
Ground = GNYE (green-yellow)

1313

A0021418

1212

A0021420

K

Yellow LED (ye) not lit
Yellow LED (ye) lit
external load

Overvoltage protection

Overvoltage category II