Endress+Hauser Nivocompact FTC 131, Nivocompact FTC 231, Nivocompact FTC 331 Technical Information

Technical
Information
TI 133F/00/en

Capacitance Limit Detection

nivocompact FTC 131/231/331

Compact level limit switches for bulk solids

FTC 131

Applications

The Nivocompact FTC… is used for limit
detection in silos containing bulk solids
(for minimum or maximum level
indication). Three versions cover almost
any measuring application:

FTC 131 with rod probe ø 25 mm,

for mounting laterally or from above.
Mainly for maximum detection of
fine-grained or powdery bulk solids.
For minimum detection in small silos
with light bulk solids.
For use in the food processing industry.

FTC 231 with rope probe ø 10 mm,

for mounting from above.
Mainly for maximum detection.
For minimum detection with light bulk
solids.

FTC 331 with rope probe ø 16 mm,

for mounting from above.
For maximum and minimum detection
with heavy bulk solids.

FTC 231

FTC 331

Advantages:

• Complete unit consisting of probe with

plug-in electronic insert:
– simple mounting, low installation

costs

– for automation and control systems

(PLC, PCS, PC, relays, contactors,
etc.)

• No moving parts in silo:

– no wear, long operating life
– no maintenance

• Simple calibration:

– variable switchpoint with probes

mounted from above

• Rope version can be easily shortened:

– can be used for various limit values
– short delivery time

Endress

Nothing beats know-how

Hauser

+

Application Examples

Sand Glass aggregate
Gravel Moulding sand
Lime Ore, crushed
Plaster Aluminium shavings
Cement Grain
Pumice Flour
Dolomite Sugar beet chips
Kaolin Fodder
and similar bulk solids

Note:
Bulk solids should have dielectric
constants ε

≥ 2.5.

r

The Complete
Measuring System

The Nivocompact is an electronic switch.
The entire measuring system consists of:

• Nivocompact FTC…

• power supply and

• connected control systems, switches,

signal transmitters
(e.g. process control systems, PLC,
relays, microcontactors, lamps, sirens
etc.)

The capacitance
level limit switches
Nivocompact
FTC 131...FTC 331
in practice

FTC 231/331

Power
supply

FTC 131

Power
supply

TI133Y01

Operation

The probe (rod or rope) and the silo wall
form the two electrodes of a capacitor,
with a high frequency voltage between
them.
The limit value is based on the principle
of a discharge circuit:
As long as the probe is in air with a
dielectric constant of ε
discharge time constant is τ = R x C

= 1, then the

r

A

where R is the resistance of the circuit
and C

the capacitance of the capacitor

A

formed by the probe and silo wall.
If bulk material with a high dielectric
constant moves into the electrical field
between the probe and silo wall, then
the capacitance C

increases and with

A

it the time constant τ.
The change in the time constant is
evaluated and the Nivocompact is
activated according to its switching
mode.

The capacitor
consisting of the silo
wall and probe

The Nivocompact is extremely
insensitive to low build-up on the probe
and silo wall as long as the material
does not form a bridge between the
probe and wall (e.g. on the threaded
boss).

εr > 1εr = 1

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2

Fail-Safe Mode

Safety
Switching

Maximum

fail-safe
mode

Level Electronic Switch

Connected

(load circuit closed)

Minimum

fail-safe
mode

Power failure

The electronic switch
operates according to
the fail-safe switching
and the level.

The built-in feature for minimum/
maximum fail-safe switching allows the
Nivocompact to be used in all
applications requiring high operational
safety:

• Maximum Fail-Safe:

The current circuit is blocked
if the probe is covered
or the power supply fails.

Full

Disconnected

(load circuit open)

Connected

(load circuit closed)

Disconnected

(load circuit open)

Empty

Disconnected

(load circuit open)

TI133Y02

• Minimum Fail-Safe:

The current circuit is blocked
if the probe is uncovered
or the power supply fails.

A red LED on the electronic insert
indicates switching status.

Main Features of the
Different Electronic
Inserts

Electrical connections
available with the
different electronic
inserts.

Electronic Insert EC 20
Two-wire AC connection
21 V…250 V
Electronic switch, max. 350 mA

Electronic Insert EC 23
Three-wire DC connection
10 V…55 V
Transistor circuit,

load connection NPN, max. 350 mA
Electronic Insert EC 22
Three-wire DC connection
10 V…55 V
Transistor circuit,
load connection PNP, max. 350 mA

Electronic Insert EC 24

with potential-free relay output,

AC voltage operation

21 V…250 V or

DC voltage operation

20 V…200 V

EC 20 EC 22 EC 23 EC 24

U

U =

U =

3

U
U =

TI133Y13

Basic Differences
Between Probes

Nivocompact FTC 131

Rod probe, ø 25 mm
Insulation PE
Probe length 350 mm

Nivocompact FTC 231

Rope probe, ø 10 mm
Insulation PA
Probe length max. 22 m
Tensile load max. 3 t

Nivocompact FTC 331

Rope probe, ø 16 mm
Insulation PVC
Probe length max. 22 m
Tensile load max. 8 t

approx.140

L = 350

(Standard)

max. 88∅

∅ 25

max. 80

60 AF

G 1½
or
NPT 1½"

Steel rod
Insulation PE

TI133E18

approx.140

Dimensions FTC 131

max. 88∅

max. 80

approx.155

60 AF

G 1½

55

∅ 20

∅ 10

or
NPT 1½"

Insulation

Steel rope
Partial insulation

100

max. 88∅

max. 80

∅ 24

∅ 16

60 AF

G 1½
or
NPT 1½"

Insulation

Steel rope
Partial insulation

L max. 22000

approx.250

Dimensions FTC 231

∅ 40

Cast iron

TI133E19

L max. 22000

Cast iron

∅ 40

approx.250

TI133E20

Dimensions FTC 331

4

Installation
General Information

Filling the Silo

The filling stream should not be directed
onto the probe.

Angle of Material Flow

Note the angle of material flow or the
outlet funnel when determining the
measuring point or probe length.

Distance Between Probes

If more than one probe is mounted in a
silo, then a minimum distance of 0.5 m
must be allowed for in order to avoid
mutual interference.

Threaded Socket for Mounting

Use the shortest possible threaded
socket when mounting the Nivocompact
FTC 131…331.
Condensation can form in long threaded
sockets and interfere with correct
operation of the probe.

Heat Insulation

With high silo temperatures:
Insulate the outside silo wall to avoid
exceeding the max. permissible
temperature of the Nivocompact
housing. This insulation also prevents
condensation near the threaded boss
and so reduces build-up and the
danger of error switching.

Installation in the Open

A protective sun cover as an accessory
protects the Nivocompact with the
aluminium housing from excessive
temperatures and from condensation
which may form in the housing due to
large temperature variations.

Distance

Angle of
slope

FTC 231
FTC 331

min.
500 mm

Angle of
slope

min.
500 mm

min.
500 mm

max. 80 °C

Protective
roof

approx.
200 mm

FTC 131

max. 60 °C

Protective
sun cover

FTC 131

TI133Y03

General information
for installing the
capacitance
Nivocompact FTC…
level limit switch.

5