Introduction; Field Of Application; Measurement Principle; Measuring System - Endress+Hauser FEC 22 Betriebsanleitung

Elektronic insert FEC 22

1 Introduction

1.1 Field of Application

The FEC 22 electronic insert is designed as a compact limit switch to be used with the
modular family of Multicap probes for limit detection of materials.
It contains all the (microprocessor-controlled) electronics necessary for limit detection
and does not require an external switching unit.
The insert is available in two versions:
• AC version with two changeover contacts (DPDT)
• DC version with PNP output
These two versions ensure that it can be used in a wide variety of applications.

1.2 Measurement principle

This limit detection system is based on the capacitive principle, where the probe and
vessel wall together form a capacitor. The area between the probe and vessel wall is
either filled with air (vessel empty) or the material to be measured (vessel full)
according to the product level. The initial capacitance of an empty vessel is much
smaller than that of a full vessel, the maximum capacitance being a function of the
dielectric constant of the material. This change in capacitance between the initial and
final capacitance values activates the limit switch at a preset level.
The FEC 22 can also be used with probes with active build-up compensation for the
measurement of liquids which have a high viscosity or tend to form crystals.
Since these media have a strong tendency to form build up on the probe, this
combination provides a reliable, maintenance-free measurement.
If extreme build-up occurs or the probe must be mounted in an unfavorable position,
a probe with screening and active build-up compensation can be used.

1.3 Measuring system

The FEC 22 electronic insert contains all the electronics for limit switching.
A complete measuring system comprises:
• FEC 22 electronic insert
• Multicap T or Multicap
probe
• power supply
• any additional signal
transmitters, switching
units, control systems
(e.g. lamps, horns,
relays, PLC, process
control systems, etc.)
Endress+Hauser
Multicap T or
Multicap probe
BA160Y11
FEC 22
contact
(relay or PNP)
U
power supply
1 Introduction
Limit detection
Active build-up
compensation
Fig. 1.1
Measuring system
27