Endress+Hauser RN22, Руководство по эксплуатации, Страница: 32 / 40

Appendix: system overview of RN Series RN22
32 Hauser
circuit, the 24 V
DC
power is supplied in this example by two RNB22 power supplies, which
provide a short-circuit current of 2 · 5.6 A = 11.2 A.
13.2 Applications of the RN Series devices
This section describes the typical applications of the RN Series devices.
These devices perform various functions during signal conditioning:
• Amplification
• Normalization
• Filtering
• Galvanic isolation
• Supply of electrical power to connected sensors
• Line monitoring
The devices for these tasks are collectively known as isolating amplifiers or signal isolators
and are available with different functions in the Hauser RN Series. Different types
of signals are conditioned in this context.
13.2.1 Types of signals
Signals are referred to as analog signals if they can continuously assume every value
between a minimum and maximum value (e.g. 0/4-20 mA) and are therefore also known
as "value-continuous" signals. The value range in this interval is huge and is practically
infinite in terms of measuring accuracy.
Electrical analog signals are generated with the help of a sensor, for example, which
records the states, or changes of state, of physical variables and converts them to an
electrical signal.
The following variables are typically measured in system and process engineering using
Hauser measuring devices:
• Temperature
• Pressure
• Level
• Flow
• Analysis values (e.g. turbidity, conductivity, pH etc.)
These analog signals are evaluated in the controller (PLC) and the signals can be used in a
"target device": e.g. for
• Display devices, e.g. level indication via RIA15
• Control unit, e.g. level control
• Actuators, e.g. to fill a tank
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.