Endress+Hauser RN22, Руководство по эксплуатации, Страница: 33 / 40

RN22 Appendix: system overview of RN Series
Hauser 33
A
B
4
20
I (mA)
A0045578
 16 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 0 mA: wire break; circuit open
• Current <1.2 mA: sensor ready, undamped
• Current >2.1 mA: sensor ready, damped
• Current maximum value >6 mA: short-circuit, maximum current
The portfolio of the RN Series offers the following function modules:
• RN22, RN42 active barrier
• RN22 signal doubler
• RLN22, RLN42 NAMUR isolating amplifier
• RNO22 output isolating amplifier
13.2.2 RN22 active barrier
The active barriers perform several functions. In addition to galvanic signal isolation and
the proportional transmission of analog 0/4-20 mA signals, they also provide power to
connected sensors. The RN22 devices are HART-transparent, i.e. they also transmit the
HART information supplied by the PMP71B. Via the HART connections on the front, HART
signals can be measured or connected "SMART" sensors can be easily configured.
The following are examples of typical applications of the RN22 active barrier. Each
application is explained briefly and described in a schematic diagram.
Example: pressure measurement in a hazardous area
• The passive 2-wire PMP71B sensor supplies a current signal, which is proportional to
the pressure, to the active input of the RN22 active barrier
• The RN22 active barrier supplies an active current output signal, which is proportional to
the input signal, to a passive input of the evaluation unit