1.1
Application
The Silometer FMX 570 is designed for level measurement with a capacitance or
hydrostatic pressure probe in safe or explosion hazardous areas. It possesses an
intrinsically-safe sensor circuit conforming to EEx ia IIC and IIB. A list of certificated
combinations is to be found in »Notes on Safety« preceding this chapter. A working
system for level measurement comprises:
•
Silometer FMX 570 transmitter,
•
Capacitance, Multicap or Deltapilot S probe
•
Electronic insert
Silometer function
The capacitance or pressure measured by the sensor is converted into a frequency
signal by the electronic insert located in its head. The Silometer FMX 570 supplies the
power and receives a level-proportional frequency signal over a two-core cable. The
signal is then processed to provide a level or volume measurement.
Fail-safe operation
If a fault condition is detected, e.g. a break in sensor - transmitter cable, the analogue
signal switches to -10 % or +110 % level or holds the last measured value. In addition,
the alarm relay de-energises.
2
1
1
FMX 570
mA1
0/4...20 mA,
0/2...10V
output
Silometer
FMX 570
transmitter
Liquids
Bulk solids
Channel 1
Ex
non-Ex
or
or
BA119Y01
Fig. 1.1:
Standard application showing
Silometer FMX 570 controlling
level measurement
➀
Capacitance probe
➁
Deltapilot
frequency
analog
digital
current
voltage
sens. [Hz/pF]
offset [Hz]
offset [pF] sens. [pF/cm]
range upper limit
V2
range lower limit
V1
frequency
electronic-
insert
electronic-
insert
capacit./
pressure
volume
V2
V1
level
volume
H2
H1
level
cap./press.
level
zero point shift
BA119E08
Fig. 1.2
Signal processing in the
Silometer FMX 570
Chapter 1: Introduction
Silometer FMX 570
6
