Appendix: system overview of RN Series
RLN42
28
Hauser
A transmitter can also be connected downstream of the sensor. This transmitter converts
the analog measured value signal to a standard signal and thereby enables the further
processing of the signal with additional standardized, electrical modules. The transmitter
can also be integrated in the sensor housing.
Binary signals
only assume two values and signal the states "on" or "off" / "1" or "0" with
these values. Binary signals are often equated with "digital" signals because digital signals
are generally binary encoded.
HART
(Highway Addressable Remote Transducer) signals are essentially characterized by
the fact that they are operated and used as a complement to classic analog standard
signals, in contrast to other digital fieldbus systems. HART therefore does not replace
point-to-point wiring but rather enables the integration of smart field devices. The digital
signals are modulated onto an analog 4 to 20 mA standard current signal using HART
modulation in order to transmit digital information in addition to the analog information
of the process value.
A
B
4
20
I (mA)
A0045578
11
Modulated HART signal
A
Analog signal
B
Digital signal
NAMUR
sensors are operated with a transmitted current and have four states so that
sensor errors can also be detected by an analog evaluation unit. This is sometimes referred
to as the "closed circuit current principle".
NAMUR sensors can adopt four states at the output:
• Current of 0 mA: wire break; circuit open
• Current below 1.2 mA: sensor ready, undamped
• Current above 2.1 mA: sensor ready, damped
• Current of maximum value above 6 mA: short-circuit, maximum current
The portfolio of the RN Series offers the following function modules:
• Active barrier
• Signal doubler
• NAMUR isolating amplifier
• Output isolating amplifier
13.2.2 RLN42 NAMUR isolating amplifier
The NAMUR isolating amplifiers isolate and convert the analog NAMUR signal of
connected proximity or limit switches to binary relay output states.
The abbreviation "NAMUR" is based on the former association name "Normen
Arbeitsgemeinschaft für Mess- und Regeltechnik in der chemischen Industrie
(Standardization Association for Measurement and Control in Chemical Industries)". While
NAMUR's subtitle has since changed, the abbreviation has been kept. NAMUR sensors are
proximity sensors or limit switches that are widely used in process automation. Endress
+Hauser offers capacitance, conductive and vibronic sensors for the various applications.
The electrical properties of sensors according to the NAMUR standard and their measuring
characteristics are standardized. Therefore, they are vendor-independent and replacement
is not restricted to the products of a specific vendor. NAMUR sensors are short-circuit