KROHNE LS 72xx EN - Manual (Page 6)

02/2013 LS 72xx 6
2 Electrical connection
External level converter module
Terminal 1 is for the electrode potential, terminal 2 for ground (housing). Wire these two
connections to the appropriate terminals of your evaluation unit (see also “Accessories“). The pin
assignment for the M12 plug connection is shown in the connection diagram. Make absolutely
sure that the sensor has no DC voltage, as this could damage the sensor or tank! The most
suitable devices are evaluators with a frequency higher than 200 Hz. Do not use devices with an
r.m.s. voltage of more than 5 V. Also pay regard to currently valid installation regulations.
With integrated level converter module
Terminals 1 and 2 are used for supplying a DC voltage of 18...36 V. According to polarity, the
output switches to active or inactive when the electrode is immersed (see connection diagram).
The terminal wired to the negative pole is connected to the housing via an internal protective
diode. The maximum power consumption is 10 mA (without load switched). This value should be
taken into account for the recommended fuse. An active switching output (pnp) is available at
terminal 3. The switching voltage is a minimum of 1 V below the supply voltage. The maximum
output current is 50 mA. At higher loads, the current is limited accordingly. Damage through
shorting cannot occur. At terminal 4 (connection “R“) the sensitivity can be set in three stages,
either by fixed wiring or by external activation for changeover in the case of product changes (see
Table). The pin assignment for the M12 plug connection is shown in the connection diagram.
Please pay regard to the respectively valid installation regulations.
R Operating
point Examples
L 200
Ω
acids, alkalis
open 2 k
Ω
beer, juice, yoghurt
L+ 20 k
Ω
(pure) water Connection diagram