1 Introduction
1.1 Application
The FEC 12 electronic insert is a transmitter for capacitive level measurement. It
converts changes in capacitance resulting from changes in level into a
capacitance-proportional impressed current. In vessels with a uniform cross section,
the level or quantity (volume) can be thus displayed as a percentage of full level or, if
a handheld terminal is used, in technical units. A pre-stored linearisation program
also allows volumes to be measured in horizontal cylinders.
The FEC 12 electronic insert is installed in the housing of the Multicap probe. It can
be used for applications in explosion hazardous areas.
Versions
Versions with corresponding features
Two versions of the FEC 12 electronic insert are available:
•
With HART protocol to be used with the Universal HART Communicator (described
in these operating instructions) and
•
With INTENSOR protocol to be used with the Commulog VU 260 Z (see operating
instructions BA 149F/00/e).
The version with the INTENSOR protocol can also be used for communication with
the Silometer FMX 770.
Features
•
Analogue output signal: standard 4...20 mA current.
•
Easy on-site settings: Settings "empty calibration" (= 4 mA) and "full calibration"
(= 20 mA) using pushbuttons on the electronic insert.
•
Operates with a linear characteristic as well as with a stored linearisation curve for
horizontal cylinders.
•
The adjustable integration time ensures stable measured values even with agitated
materials.
1.2 Measuring System
The measuring system consists of a
capacitive Multicap level probe and an
FEC 12 electronic insert. A DC power
supply is also required. The two-wire
power cable is also used for signal
transmission, and delivers a 4...20 mA
signal with a superimposed bidirectional
digital signal conforming to the HART
protocol. The superimposed signal has
no influence on the follow-up
instrumentation.
1.3 Operating Principle
Capacitive measurement functions as follows: the probe and vessel wall form a
capacitor. Depending on the level, the space between these "capacitor plates" is filled
either with air (empty vessel) or an unspecified quantity of material. The initial
capacitance for the empty vessel is low but increases proportionally to the amount of
material covering the probe.
4...20 mA with
digital signal
e.g. display
e.g. plotter
DC power
supply or
PLC
Multicap
probe
Fig. 2
Measuring system:
the electronic insert is used in a
Multicap probe for capacitive
measurement.
Electronic insert FEC 12 (HART)
1 Introduction
Hauser
3
