Two-rod capacitive probe for continuous level measurement in liquids

Liquicap T FMI21

11-35 Pcs.


  • No calibration needed (preconfigured from factory 0 to 100 % to ordered probe length)

  • Corrosion resistant materials (carbon fiber, stainless steel)

  • Simply shorten the probe rods on site

  • Safe operation - regardless of tank geometry


Conductive liquids as of

30 μS/cm



Probe length:

150 to 2500 mm

Product temperature:

-40 to +100 °C

Process pressure:

-1 to +10 bar


Max. 2000 cSt

Product/VersionPrice/pcs. in NZ$Order code
Capacitive rod probe
ApprovalProbe Length; MaterialElectronics; Output1 to 34 to 1011 to 35
Non-hazardous area2000mm L; PP >316 With Shortening KitFEI20; 4-20mA + display840.-781.-739.-FMI21-A1A1C2
The above model is ex stock. Please ask for pricing and delivery time of other FMI21 versions.

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 Liquicap T FMI21 sensor is used in conductive liquids for continuous level measurement. The Liquicap T FMI21 is particularly suited to small measuring tanks and works independently of the tank's shape or material (plastic, stainless steel, concrete…).

It is resistant to aggressive liquids like acids or alkalis.


The probe and medium form an electric capacitor. If the probe is in air, a certain low initial capacitance is measured. When the tank is filled, the capacitance increases the more the probe is covered. The electronic insert of the probe converts the capacitance measured to a 4-20mA signal in proportion to the level.


Application example

a) Factory calibration

b) Transmitter power supply


The measuring system consists of:

  • The Liquicap T FMI21 capacitance probe (the probe rods should never be in contact with the tank) with
  • Electronic insert FEI20
  • Display and housing cover (optional)
  • A transmitter power supply unit such as RIA45/RIA46 or RIA452. Ask us about other Endress+Hauser transmitter supply units.

Technical Data

  • Maximum viscosity
2000 cSt
  • Measuring range

0 pF to 2000 pF

  • Probe length

150 to 2500 mm

  • Permitted span

∆C = 10 pF to 2000 pF

  • Measuring frequency
250 kHz
  • Input signal

Probes covered => high capacitance

Probes exposed => low capacitance

Output (electronic insert FEI20/4 to 20mA)
  • Output signal

3.8 to 20.5 mA

  • Switch-on current
max. 20 mA (< 500 ms)
  • Signal on alarm

> 21 mA

Power supply
  • Connection voltage
U = 10 to 30 V DC, reverse polarity protection (integrated)
  • Power consumption
P < 0.7 W
  • Current consumption
I < 22 mA
  • Cable entries

M20×1.5 (screw connection)

Performance characteristics (with installed electronic insert)

  • Reference operating conditions
Ambient temperature 23 °C, atmospheric pressure, probe installation vertical from above
  • Max. measured error

≤ 1 % of full scale value (0 to 2000 pF)

  • Repeatability
0.25 % of full scale value (0 to 100 pF)
  • Start-up settling time
< 2 s
  • Influence of ambient temperature

< 0.01 %/K (-40 to +70 °C) probe length 1 m

  • Integration time
1 s
  • Calibration

In an installed state, recalibration is only necessary if:

  • the 0 % and 100 % value should be adjusted to suit customer specifications
  • after the probe rods have been shortened
Operating conditions
  • Ambient temperature

-40 to +70 °C

  • Storage temperature

-40 to +80 °C

  • Climate class
Tropicalized as per DIN IEC 68 Part 2-38
  • Degree of protection
IP 66
  • Shock resistance

DIN EN 60068-2-27/IEC 68-2-27: 30g

  • Vibration resistance

DIN EN 60068-2-64/IEC 68-2-64:

20 to 2000 Hz, 1 (m/s²)² /Hz (with min. rod length 150 mm)

  • EMC
Interference emission to EN 61326, electrical equipment class B; Interference immunity to EN 61326, annex A (industrial)
  • Conductivity of medium

≥ 30 µS/cm

  • Process pressure

-1 to +10 bar

  • Process temperature

-40 to +100 °C

  • Lateral loading capacity

2 Nm

Materials in contact with medium
  • Probe rods

Rod: 1.4404/316L; Optional: carbon fiber CFC;

Sealing ring: EPDM;

Insulation: PP;

Spacer: PP

  • Process connections
G 1 ½ A (PPS, DIN ISO 228/l)
  • Seals

Sealing ring for process connection

G 1½ A: Elastomer fiber asbestos-free (resistant to oils, solvents, steam, weak acids and alkalis)

  • Green LED

operational status (slow flashing), calibration status (fast flashing)

  •  Red LED
for key enter validation (short flashing), alarm or warning (flashing);display for measured value in % (optional)
  • WHG approval
Overspill protection to §19 WHG (Germany)
  • Ex approval

Dimensions (in mm)


a) SW/AF 55

b) Ground rod (uninsulated)

c) Probe rod insulated

L = Probe length


Installation according to operation instructions

Electrical connection

Endress+Hauser transmitter power supply with optional measurement display

Technical Datasheet