# Function and system design. ENDRESS+HAUSER Levelflex FMP55

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Measuring principle

Levelflex FMP55

## Function and system design

The Levelflex is a "downward-looking" measuring system that functions according to the ToF method (ToF =

Time of Flight). The distance from the reference point to the product surface is measured. High-frequency pulses are injected to a probe and led along the probe. The pulses are reflected by the product surface, received by the electronic evaluation unit and converted into level information. This method is also known as TDR (Time

Domain Reflectometry).

For interface applications this method is combined with a capacitive measurement.

R

D

L

LN

D

I

L

L

UP

L

I

DK

1

( DC

1

)

100%

F

E

0%

A0011177

R = reference point of measurement D

L

= distace level complete

E = empty calibration (= zero) L

L

= level complete

F = full calibration (= span)

LN = probe length

D

I

= distance interface (distance flange / DC

2

)

L

I

= level interface (distance probe end / DC

1

)

UP = thickness upper medium

Dielectric constant

The dielectric constant (DC) of the medium has a direct impact on the degree of reflection of the highfrequency pulses. In the case of large DC values, such as for water or ammonia, there is strong pulse reflection while, with low DC values, such as for hydrocarbons, weak pulse reflection is experienced.

Eingang

The reflected pulses are transmitted from the probe to the electronics. There, a microprocessor analyzes the signals and identifies the level echo which was generated by the reflection of the high-frequency pulses at the product surface. This clear signal detection system benefits from over 30 years' experience with pulse time-offlight procedures that have been integrated into the development of the PulseMaster® software.

The distance D to the product surface is proportional to the time of flight t of the impulse:

D = c · t/2, where c is the speed of light.

Based on the known empty distance E, the level L is calculated:

L = E – D

The reference point R of the measurement is located at the process connection. For details see the dimensional drawing:

FMP55: (® ä 32)

The Levelflex possesses functions for interference echo suppression that can be activated by the user. They guarantee that interference echoes from e.g. internals and struts are not interpreted as level echoes.

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Levelflex FMP55

Output

The Levelflex is preset at the factory to the probe length ordered so that in most cases only the application parameters that automatically adapt the device to the measuring conditions need to be entered. For models with a current output, the factory adjustment for zero point E and span F is 4 mA and 20 mA, for digital outputs and the display module 0 % and 100 %. A linearization function with max. 32 points, which is based on a table entered manually or semi-automatically, can be activated on site or via remote operation. This function allows the level to be converted into units of volume or mass, for example.

Interface measurement

When the high-frequency pulses hit the surface of the medium, only a percentage of the transmission pulse is reflected. In the case of media with a low DC

1

, in particular, the other part penetrates the medium. The pulse is reflected once more at the interface point to a second medium with a higher DC

2

. The distance to the interface layer now can also be determined taking into account the delayed time-of-flight of the pulse through the upper medium.

In addition to this, FMP55 measures the capacitance of the probe. This enables interface measurements even if the second echo is missing due to an emulsion layer between the two phases.

DK

1

( DC

1

)

R

L

L

C

0

DK

1

L

I

A0011178

L

L

= level complete

L

I

= level interface

R = reference point of measurement

In addition, the following general conditions must be observed for interface measurement:

• The DC of the upper medium must be known and constant

1)

. The DC can be determined with the aid of

the DC manual SD106F. In addition, whenever the interface thickness is existing and known, the DC can be calculated automatically via FieldCare.

• The DC of the upper medium may not be greater than 10.

• The DC difference between the upper medium and lower medium must be >10.

• The interface must have a minimum thickness of 80 mm.

• Conductivity of the upper medium: < 1 mS/cm

• Conductivity of the lower medium: > 100 mS/cm

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Levelflex FMP55

Life cycle of the product

Engineering Procurement Installation

Commissioning Operation

Maintenance Retirement

A0013773-EN

å

1 Life cycle process

Engineering

• Universal measuring principle

• Measurement unaffected by medium properties

• Hardware and software developed according to SIL IEC 61508

• Genuine, direct interface measurement

Procurement

• Endress+Hauser being the world market leader in level measurement guarantees asset protection

• Worldwide support and service

Installation

• Special tools are not required

• Reverse polarity protection

• Modern, detachable terminals

• Main electronics protected by a separate connection compartment

Commissioning

• Fast, menu-guided commissioning in only 6 steps

• Plain text display in national languages reduces the risk of error or confusion

• Direct local access of all parameters

• Short instruction manual at the device

Operation

• SensorFusion provides redundant measurement for highest safety

• Multi-echo tracking: Reliable measurement through self-learning echo-search algorithms taking into account the short-term and long-term history in order to check the found echoes for plausibility and to suppress interference echoes.

• Diagnostics in accordance with NAMUR NE107

Maintenance

• HistoROM: Data backup for instrument settings and measured values

• Exact instrument and process diagnosis to assist fast decisions with clear details concerning remedies

• Intuitive, menu-guided operating concept in national languages saves costs for training, maintenance and operation

• Cover of the electronics compartment can be opened in hazardous areas

Retirement

• Order code translation for subsequent models

• RoHS-conforming (Restriction of certain Hazardous Substances), unleaded soldering of electronic components

• Environmentally sound recycling concept

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Levelflex FMP55

Measuring system General notes on probe selection

• For interface measurement, ideally coax probes or rod probes in a bypass/stilling well are used.

• Coax probes are suited to liquids with viscosities of up to approx. 500 cst. Coax probes can measure most liquefied gases, as of a dielectric constant of 1.4. Moreover, installation conditions, such as nozzles, tank internal fittings etc., have no effect on the measurement when a coax probe is used. A coax probe offers maximum EMC safety when used in plastic tanks.

• Rod or rope probes for free installation in the tank available on request.

Rope probes may also be used in a bypass/stilling well, if the distance to the ceiling is too small for mounting a rod probe and if it can be excluded that the rope or end-of-probe weight touches the wall of the tube

(diameter large enough, precisely vertical tube).

Probe selection

The various types of probe in combination with the process connections are suitable for the following applications:

Type of probe Rod probe

Levelflex FMP55

Rope probe Coax probe

Feature 060 - Probe:

Max. probe length

For application

A0011357

A0011358

Option: Option:

CA 16 mm (PFA>316L) NA 4 mm (PFA>316)

CB 16 mm (PFA>316L) ND 1/6" (PFA>316)

Option:

UA ... mm (316L)

UB ... inch (316L)

4 m (13 ft) 10 m (33 ft) level and interface measurement in liquids

6 m (20 ft)

A0011359

If required, rod and rope probes can be replaced. They are secured with a thread coating.

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### Key Features

• Coated multiparameter probe
• Redundant measuring system
• Measuring range up to 10m
• Factory precalibrated
• Simple integration
• ATEX, IEC Ex, CSA, FM approvals