KROHNE OPTISYS TUR 1050 EN - Manual (Page 25)

ELECTRICAL CONNECTIONS
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OPTISYS TUR 1050
www.krohne.com 11/2012 - 4002444301 MA OPTISYS TUR 1050 R02 en
4.5.2 Alarms terminal (signal output)
The terminals "ALARM 1" and "ALARM 2" are mechanical relays rated at 240 VAC and 2 A. The
abbreviations on the board and below the terminal have the following meanings:
• NO: Normally open
• NC: Normally closed
• C: Common
As the configuration of the alarms is fail-safe, the normal state is a power supplied device and
non-active alarms. For detailed information concerning the configuration of the alarms refer to
Configuring the alarm relays on page 39.
4.5.3 RS 485 or 4...20 mA signal output
The 4...20 mA output is energised by a 15 VDC power source and can drive recorder loads up to
600 Ω. It is isolated from line power and earth ground.
The RS 485 half-duplex digital interface (2-wire) operates with differential levels that are
unsusceptible to electrical interferences. This is why the usage of cable lengths up to
900 m / 2950 ft is possible. Independent of the output mode (analog or digital) always note the
following items:
• For ease of connecting, remove the plug in terminal block (the labels of the connections are
beneath this block).
• Do not run 4...20 mA or RS 485 cables in the same conduit as power as this could lead to
signal interferences.
• When using the RS 485 interface, equip the last device on each bus with a 120 Ω terminating
resistor to eliminate signal reflection on the line.
INFORMATION!
The installation of the 4...20 mA isolator will render the RS 485 non-operational. Shifting
between the 4...20 mA (analog) and the RS 485 (digital) output mode works with the help of the
software, for further information refer to Selecting the output on page 36
.
INFORMATION!
Transformer isolated outputs are available as a factory installed option.